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Lumefantrine plasma concentrations in uncontrolled conditions among patients treated with artemether-lumefantrine for uncomplicated plasmodium falciparum malaria in Mwanza, Tanzania

Open AccessPublished:September 02, 2022DOI:https://doi.org/10.1016/j.ijid.2022.08.020

      Abstract

      Background

      Therapeutic efficacy of artemether-lumefantrine is highly dependent on adequate systemic exposure to the partner drug lumefantrine particularly day 7 lumefantrine plasma concentration. There has been contradicting findings on the role of the cut-off values in predicting treatment outcomes among malaria patients in malaria endemic regions. This study assesses the day 3 and 7 lumefantrine plasma concentrations including related determinant factors and their influence on treatment outcomes among treated Tanzanian children and adults in uncontrolled conditions (real life condition).

      Methods

      Data was nested from an efficacy study employing the WHO protocol, 2015 for monitoring antimalarial drug efficacy. Lumefantrine plasma concentration was measured by high performance liquid chromatography with ultraviolet (HPLC-UV). Results: Lumefantrine plasma concentrations below 175ng/ml and 200ng/ml on day 3 and 7 did not affect adequate clinical and parasitological response (ACPR) and recurrence of infection (p = 0.428 and 0.239 respectively). Age and baseline parasitemia were not associated to day 3 median lumefantrine plasma concentrations (p = 0.08 and 0.31 respectively) and day 7 lumefantrine plasma concentrations (p = 0.07 and 0.41 respectively). However, the day 3 and day 7 lumefantrine plasma concentrations were significantly higher in males compared to females (p = 0.03 and 0.042 respectively).

      Conclusion

      Lumefantrine plasma concentrations below cut-off points (175ng/ml and 200ng/ml) on day 3 and 7 did not influence treatment outcomes.

      Keywords

      Abbreviations:

      ACT (Artemisinin-based combination therapy), DHP (Dihydroartemisinin-piperaquine), ALU (Artemether-lumefantrine), ACPR (Adequate Clinical and Parasitological Response), ETF (Early Treatment Failure), LCF (Late Clinical Failure), HPLC-UV (High performance liquid chromatography with ultra-violet), LPF (Late Parasitological Failure), WHO (World Health Organization)

      Introduction

      Sub-Saharan countries including Tanzania are the most affected with the burden of Plasmodium falciparum (P. falciparum) malaria. Treatment response in P. falciparum malaria is influenced by a vast number of factors. Such factors can be classified as drug quality, pharmacokinetic characteristics of individual drug, parasite sensitivity and host genetics (
      • Obua C.
      • Hellgren U.
      • Ntale M.
      • Gustafsson L.L.
      • Ogwal-Okeng J.W.
      • Gordi T.
      • Jerling M.
      Population pharmacokinetics of chloroquine and sulfadoxine and treatment response in children with malaria: suggestions for an improved dose regimen.
      ). Artemether-lumefantrine (ALU) is the most used artemisinin-based combination therapy (ACT) as first line drug in malaria endemic countries (
      • Organization W.H.
      Guidelines for the treatment of malaria.
      ). The rapid parasite clearance is associated with artemether whereas lumefantrine plays a significant role in clearing the remaining parasites after two parasite asexual cycles have been exposed to artemether (
      • Kloprogge F.
      • McGready R.
      • Hanpithakpong W.
      • Blessborn D.
      • Day N.P.
      • White N.J.
      • Nosten F.
      • Tarning J.
      Lumefantrine and desbutyl-lumefantrine population pharmacokinetic-pharmacodynamic relationships in pregnant women with uncomplicated Plasmodium falciparum malaria on the Thailand-Myanmar border.
      ). Artemether which is a lipid soluble derivative of dihydroartemisinin is quickly absorbed and transformed to the active metabolite dihydroartemisinin (DHA). The peak concentrations of artemether and DHA are obtained within 2 hours after administration resulting to rapid reduction in asexual parasites biomass and quick resolution of symptoms (
      • Djimdé A.
      • Lefèvre G.
      Understanding the pharmacokinetics of Coartem®.
      ;
      • White N.J.
      • van Vugt M.
      • Ezzet F.D.
      Clinical pharmacokinetics and pharmacodynamics of artemether-lumefantrine.
      ). Lumefantrine is highly lipophilic with 98% binding to plasma lipoproteins and fat (
      • Chotivanich K.
      • Mungthin M.
      • Ruengweerayuth R.
      • Udomsangpetch R.
      • Dondorp A.M.
      • Singhasivanon P.
      • Pukrittayakamee S.
      • White N.J.
      The effects of serum lipids on the in vitro activity of lumefantrine and atovaquone against Plasmodium falciparum.
      ). The bioavailability of lumefantrine is increased by concurrent uptake of fat meals (
      • Ashley E.A.
      • Stepniewska K.
      • Lindegårdh N.
      • Annerberg A.
      • Kham A.
      • Brockman A.
      • Singhasivanon P.
      • White N.J.
      • Nosten F.
      How much fat is necessary to optimize lumefantrine oral bioavailability?.
      ;
      • Djimdé A.
      • Lefèvre G.
      Understanding the pharmacokinetics of Coartem®.
      ;
      • Organization W.H.
      Guidelines for the treatment of malaria.
      ). The terminal elimination half-lives of artemether and lumefantrine are ≤ 1 hour and 3-5 days respectively (
      • Ashley E.A.
      • Stepniewska K.
      • Lindegårdh N.
      • McGready R.
      • Annerberg A.
      • Hutagalung R.
      • Singtoroj T.
      • Hla G.
      • Brockman A.
      • Proux S.
      Pharmacokinetic study of artemether–lumefantrine given once daily for the treatment of uncomplicated multidrug-resistant falciparum malaria.
      ;
      • Djimdé A.
      • Lefèvre G.
      Understanding the pharmacokinetics of Coartem®.
      ). The elimination of lumefantrine is very slow in healthy volunteers than in patients with malaria (terminal half-life 2-3 days vs 4-6 days) (
      • Djimdé A.
      • Lefèvre G.
      Understanding the pharmacokinetics of Coartem®.
      ;
      • Ezzet F.
      • Van Vugt M.
      • Nosten F.
      • Looareesuwan S.
      • White N.
      Pharmacokinetics and pharmacodynamics of lumefantrine (benflumetol) in acute falciparum malaria.
      ). The slow elimination of lumefantrine plays a great role in the elimination of residual parasites after artemether and DHA have been cleared thus preventing recrudescence (
      • Djimdé A.
      • Lefèvre G.
      Understanding the pharmacokinetics of Coartem®.
      ;
      • White N.J.
      • van Vugt M.
      • Ezzet F.D.
      Clinical pharmacokinetics and pharmacodynamics of artemether-lumefantrine.
      ) due to parasite's exposure to high levels of lumefantrine concentrations resulting from accumulation owing to a long half-life of the drug (
      • White N.J.
      • van Vugt M.
      • Ezzet F.D.
      Clinical pharmacokinetics and pharmacodynamics of artemether-lumefantrine.
      ).
      The suggested pharmacokinetics determinants of treatment outcomes in P. falciparum uncomplicated malaria are area under the curve (AUC) and day 7 plasma concentrations of partner drugs in ACT. However, some studies report day 3 plasma lumefantrine concentrations as a strong predictor of treatment outcome in infants and young children (
      • Tchaparian E.
      • Sambol N.C.
      • Arinaitwe E.
      • McCormack S.A.
      • Bigira V.
      • Wanzira H.
      • Muhindo M.
      • Creek D.J.
      • Sukumar N.
      • Blessborn D.
      Population pharmacokinetics and pharmacodynamics of lumefantrine in young Ugandan children treated with artemether-lumefantrine for uncomplicated malaria.
      ). A single plasma lumefantrine concentration on day 7 is a proven best correlate of the plasma AUC (
      • Ezzet F.
      • Mull R.
      • Karbwang J.
      Population pharmacokinetics and therapeutic response of CGP 56697 (artemether+ benflumetol) in malaria patients.
      ;
      • White N.J.
      • van Vugt M.
      • Ezzet F.D.
      Clinical pharmacokinetics and pharmacodynamics of artemether-lumefantrine.
      ). Day 7 lumefantrine concentration has been suggested to be a better determinant of therapeutic response than AUC when the two are compared (
      • White N.J.
      • Stepniewska K.
      • Barnes K.
      • Price R.N.
      • Simpson J.
      Simplified antimalarial therapeutic monitoring: using the day-7 drug level?.
      ) although some studies report the opposite (
      • Parikh S.
      • Kajubi R.
      • Huang L.
      • Ssebuliba J.
      • Kiconco S.
      • Gao Q.
      • Li F.
      • Were M.
      • Kakuru A.
      • Achan J.
      Antiretroviral choice for HIV impacts antimalarial exposure and treatment outcomes in Ugandan children.
      ). The documented therapeutic day 7 lumefantrine concentrations range between 175ng/ml and 500ng/ml. Price et al specified even a lower day 7 concentration (175ng/mL) is a predictor for treatment response (
      • Price R.N.
      • Uhlemann A.-C.
      • van Vugt M.
      • Brockman A.
      • Hutagalung R.
      • Nair S.
      • Nash D.
      • Singhasivanon P.
      • Anderson T.J.
      • Krishna S.
      Molecular and pharmacological determinants of the therapeutic response to artemether-lumefantrine in multidrug-resistant Plasmodium falciparum malaria.
      ). However, the big question is whether these commonly used cutoff values are applicable to all regions.
      Metabolism of drugs determines the plasma concentrations hence treatment response. Lumefantrine is metabolized mainly by cytochrome P450 (CYP) enzyme system, the CYP3A4 and CYP3A5 isoenzymes. The CYP3A4 gene is located on chromosome 7q21.3-q22.1 consisting of 13 exons (
      • Keshava C.
      • McCanlies E.C.
      • Weston A.
      CYP3A4 polymorphisms—potential risk factors for breast and prostate cancer: a HuGE review.
      ). The most important single nucleotide polymorphism (SNP) within the CYP3A4 family is CYP3A4*1B (rs2740574) (
      • Alessandrini M.
      • Asfaha S.
      • Dodgen T.M.
      • Warnich L.
      • Pepper M.S.
      Cytochrome P450 pharmacogenetics in African populations.
      ), an A to G transition at nucleotide 392 in the promoter sequence of the gene (
      • El-Shair S.
      • Al Shhab M.
      • Zayed K.
      • Alsmady M.
      • Zihlif M.
      Association Between CYP3A4 and CYP3A5 Genotypes and Cyclosporine's Blood Levels and Doses among Jordanian Kidney Transplanted Patients.
      ). This SNP is associated with poor metabolism of artemether and lumefantrine (
      • Staehli Hodel E.M.
      • Csajka C.
      • Ariey F.
      • Guidi M.
      • Kabanywanyi A.M.
      • Duong S.
      • Decosterd L.A.
      • Olliaro P.
      • Beck H.P.
      • Genton B.
      Effect of single nucleotide polymorphisms in cytochrome P450 isoenzyme and N-acetyltransferase 2 genes on the metabolism of artemisinin-based combination therapies in malaria patients from Cambodia and Tanzania.
      ;
      • Piedade R.
      • Gil J.P.
      The pharmacogenetics of antimalaria artemisinin combination therapy.
      ). CYP3A5*3 (rs776746) is the most important SNP in the CYP3A5 gene involving a replacement of a nucleotide adenine by nucleotide guanine at locus 6986 within intron 3 creating a mRNA splice defect thus a premature stop codon (
      • Eng H.-S.
      • Mohamed Z.
      • Calne R.
      • Lang C.
      • Mohd M.
      • Seet W.-T.
      • Tan S.-Y.
      The influence of CYP3A gene polymorphisms on cyclosporine dose requirement in renal allograft recipients.
      ;
      • Tang H.-L.
      • Ma L.-L.
      • Xie H.-G.
      • Zhang T.
      • Hu Y.-F.
      Effects of the CYP3A5* 3 variant on cyclosporine exposure and acute rejection rate in renal transplant patients: a meta-analysis.
      ). The CYP3A5*3 is involved in the metabolism of artemether, lumefantrine, mefloquine, primaquine and chloroquine (
      • Dandara C.
      • Swart M.
      • Mpeta B.
      • Wonkam A.
      • Masimirembwa C.
      Cytochrome P450 pharmacogenetics in African populations: implications for public health.
      ).
      Interindividual variability in the extent and rate of absorption, metabolism, distribution, plasma protein binding and elimination has been shown to influence the plasma concentration of drugs hence affecting treatment outcomes in turn (
      • Pang K.S.
      Modeling of intestinal drug absorption: roles of transporters and metabolic enzymes (for the Gillette Review Series).
      ). Interindividual variability is common in Africa since African populations are genetically diverse and heterogenous (
      • Bolaji O.O.
      • Adehin A.
      • Adeagbo B.A.
      Pharmacogenomics in the Nigerian population: the past, the present and the future.
      ;
      • Campbell M.C.
      • Tishkoff S.A.
      African genetic diversity: implications for human demographic history, modern human origins, and complex disease mapping.
      ;
      • Kampira E.
      • Kumwenda J.
      • J van Oosterhout J.
      • Chaponda M.
      • Dandara C.
      Pharmacogenetics research developments in Africa: a focus on Malawi.
      ) due to complex patterns of populations expansion, contraction, migration and admixture during evolutionary history (
      • Dandara C.
      • Swart M.
      • Mpeta B.
      • Wonkam A.
      • Masimirembwa C.
      Cytochrome P450 pharmacogenetics in African populations: implications for public health.
      ). Indeed, Africa is regarded as a birth place for genetic diversity (
      • Pillai G.
      • Davies G.
      • Denti P.
      • Steimer J.L.
      • McIlleron H.
      • Zvada S.
      • Chigutsa E.
      • Ngaimisi E.
      • Mirza F.
      • Tadmor B.
      Pharmacometrics: opportunity for reducing disease burden in the developing world: the case of Africa.
      ). There is a need to assess ACTs plasma concentrations in these populations since the plasma concentrations determine the extent of parasite exposure to the drug and treatment outcomes.
      Despite the wide spread use of ALU in the country there is scanty information on the drug's plasma levels and its influence on the treatment outcomes in the population. This study focuses on the day 3 and 7 lumefantrine plasma concentrations including the related determinant factors and their influence on the treatment outcomes among children and adults treated with ALU in Tanzania.

      Methods

      Study area, patient enrollment and drug administration

      The study was conducted in Igombe, Mwanza, Tanzania, the sentinel sites for conducting therapeutic efficacy studies on antimalarial drugs. The area is semi-urban and malaria meso-endemic. Patients who were P. falciparum positive after microscopy and malaria rapid diagnostic test and met the inclusion criteria as per the World Health Organization (WHO) protocol for assessment of antimalarial efficacy were enrolled after a written informed consent. Full clinical examination was performed and blood samples were taken for parasite count, hematocrit and random blood glucose determination. Malaria patients with symptoms of severe malaria according to the WHO case definition, comorbid infection(s), malnutrition, chronic diseases, history of drug allergy, history of traditional herbs use in the past 4 weeks, any antimalarial drug use in the past 4 weeks, known liver dysfunction or disease and severe anaemia were excluded from this study to avoid interference with pharmacokinetics parameters and treatment outcomes.
      A standard 6-dose of artemether 20mg -lumefantrine 120mg (Coartem®, Novartis, Switzerland) was administered as per manufacturer's dosing schedule based on body weight. Participants were not restricted on their routine diet.

      Sample collection and follow up

      Samples were collected from efficacy study which involved 35 days follow up as per the WHO protocol, 2015 for monitoring antimalarial drug efficacy (
      • Organization W.H.
      World malaria report 2015.
      ). Blood from finger pricks was collected on filter paper (FTA®Whatman paper) then dried at room temperature and stored on plastic bags on day 0,1,2,3,7,14,21,28,35 for PCR genotyping of Merozoite Surface Protein 1 (MSP1) and Merozoite Surface Protein 2 (MSP2) to distinguish between recrudescence and reinfection. Venous blood (2mls) was also collected, centrifuged at 300xg for 10 minutes and stored in cryotubes at -20°C at the clinic for few hours during the visits before final storage at -80°C at the National Institute for Medical Research (NIMR). Samples were then shipped on dry ice to the Makerere University analytical laboratory for bioanalytical measurements after storage at -80°C. Thick and thin blood smears were stained by Giemsa (on each day of the visit) according to the WHO standard protocol (
      • Organization W.H.
      Basic malaria microscopy: Part I. Learner's guide.
      ). Parasite identification and counting were done by two independent experienced microscopists.

      Genotyping and plasma lumefantrine assay

      DNA was extracted from dried blood spots (DBS) using the Invitrogen Genomic DNA extraction kit (Thermo Scientific) according to the manufacturer's instructions. Nested PCR was done to identify MSP1 and MSP2 allele variants using a method described previously (
      • Somé A.F.
      • Bazié T.
      • Zongo I.
      • Yerbanga R.S.
      • Nikiéma F.
      • Neya C.
      • Taho L.K.
      • Ouédraogo J.-B.
      Plasmodium falciparum msp 1 and msp 2 genetic diversity and allele frequencies in parasites isolated from symptomatic malaria patients in Bobo-Dioulasso.
      ). The results were classified as recrudescence or reinfection according to the WHO guideline (
      • Organization W.H.
      Methods and techniques for clinical trials on antimalarial drug efficacy: genotyping to identify parasite populations: informal consultation organized by the Medicines for Malaria Venture and cosponsored by the World Health Organization.
      ). Lumefantrine in plasma was measured by high performance liquid chromatography with ultraviolet (HPLC-UV). Chromatographic conditions were adapted from a previously published method (
      • Khuda F.
      • Iqbal Z.
      • Shah Y.
      • Ahmmad L.
      • Nasir F.
      • Khan A.Z.
      • Shahbaz N.
      Method development and validation for simultaneous determination of lumefantrine and its major metabolite, desbutyl lumefantrine in human plasma using RP-HPLC/UV detection.
      ). Quality control samples to assess precision and accuracy were set to 170, 265 and 500 ng/ml. Measurements of plasma samples in each batch of run were compared to the quality control samples. The lower limit of quantification (LOQ) and lower limit of detection(LLOD) were 18 and 12 ng/ml respectively. Intra- and inter-day coefficient of variation values were < 5%.

      Treatment outcomes

      Patients were assessed on day 0,1,2,3,7,14,21 and 28 for efficacy. The WHO 2015 protocol (

      Organization, W.H., 2015b. Methods for surveillance of antimalarial drug efficacy. 2009.

      ) was used to classify treatment outcomes as early treatment failure (ETF), late clinical failure (LCF), late parasitological failure and adequate clinical and parasitological response (ACPR). Treatment failures were classified as recrudescence or reinfection after PCR correction.

      Statistical analysis

      Ms-Excel was used for data entry and cleaning. All statistical analyses were performed using STATA version 13.1 (Statistical Corporation, College Station, TX, US). Descriptive statistics were used accordingly. Numeric variables were summarized using mean (SD) or median (IQR) Categorical data were compared using chi square tests or fisher exact tests where appropriate. Student t-test was used to compare continuous data for two groups where necessary. Per-protocol analysis was carried, patients who withdrew from the study or were lost to follow up or had reinfection were not included in the denominator. The difference between the median values were assessed using the Mann–Whitney U-test or Kruskal– Wallis test whereas student t-test was used to assess the mean difference. Exact logistic regression was used to estimate odds ratio and 95% confidence intervals for association between day 3 lumefantrine plasma concentration, day 7 lumefantrine plasma concentration with age group (children vs adults), sex (female vs male), and baseline parasitaemia. Tests of significance were performed using the 0.05 level to infer significance.

      Results

      In this study, venous blood samples were collected from 93 patients with uncomplicated P. falciparum malaria among 365 who were followed up to 35 days during the ALU efficacy study (published elsewhere). The median age of participants was 12 years and more than half (56.9%) were female. Details of the participants are provided on the Table 1 below.
      Table 1Participant characteristics at enrollment.
      CharacteristicCategoryvalues
      Age (years), median (IOR)12(4,17)
      Gender (female) n (%)Males40/93 (43.1%)
      Females53/93 (56.9%)
      Weight (Kg), mean (SD)<10 years15.38 (7.73)
      ≥10 years49.82 (17.38)
      Hemoglobin (g/dL), mean (SD)<10 years9.56 (1.24)
      ≥10 years11.10 (1.44)
      Random blood glucose<10 years5.1(0.72)
      ≥10 years5.02(0.89)
      Hepatitis B0/93(0%)
      Parasitemia (parasite/µl), geometric mean5044.2
      Residual lumefantrine plasma concentration18/93(19.4%)

      Lumefantrine plasma concentration

      Participants had at least two pharmacokinetic samples on day 0, 1, 3, 7 or 14. Residual lumefantrine plasma concentration was recorded in 19.4% of the patients where by the median concentration was 357ng/ml. The median day 0 concentration for all patients was 67ng/ml. The median day 1, 2, 3, 7 and 14 lumefantrine concentrations were 817ng/ml, 1,065ng/ml, 859ng/ml, 238ng/ml and 95ng/ml respectively.
      Sex was significantly associated with both day 3 and 7 lumefantrine plasma concentrations below the minimum cutoff values (p = 0.03 &0.042 respectively) (Figure 1). Age was not significantly associated with day 3 and day 7 lumefantrine concentrations below the minimum cut-off values (p = 0.084 and 0.071) (Figure 1). The day 3 and 7 lumefantrine plasma concentrations were not significantly influenced by the day 0 base line parasitemia (p = 0.313 and 0.413 respectively) (Figure 1). Sex of a patient showed a significant association with day 7 plasma concentration. That is, male patients had more than 4 times odds of lumefantrine plasma concentration about 200ng/ml compare to female patients. However, this association was not found with day 3 plasma concentration (Table 2).
      Figure 1
      Figure 1Day 3 and Day 7 lumefantrine plasma concentrations in relation to age, sex and baseline parasitemia.
      Table 2Day 3 and Day 7 Lumefantrine plasma concentrations in relation to age sex and baseline parasitemia.
      CharacteristicsDay 3 Lumefantrine plasma concentrationDay 7 Lumefantrine plasma concentration
      OR95%CIP valueOR95%CIP value
      Age group
       <=10 yearsRefRef
       >10 years2.2510.418-15.6510.4671.2320.346-4.5500.937
      Sex
       FemaleRefRef
       Male1.5870.293-11.0350.8164.6891.251-20.2720.018
      Baseline Parasitemia
       <=3999RefRef
       4000-200002.0160.231-+inf0.5620.5150.047-3.0450.696
       >200000.2170.031-1.2980.1040.9350.178-4.1271.000

      Treatment outcomes

      We assessed the association of day 3 and 7 lowest cut-off lumefantrine plasma concentration (175ng/ml) and the most commonly used cut-off lumefantrine plasma concentration (200ng/ml) with day 28-day outcomes. Day 3 lumefantrine plasma concentration below the minimum cut-off values predicting treatment response (175ng/ml) was not associated with low ACPR (p = 0.433). Day 7 lumefantrine plasma concentration below the minimum cut-off values (175ng/ml) was also not associated with low ACPR compared to concentration above the 175ng/ml values (p = 0.313) (Figure 2). Both lumefantrine plasma concentrations below 200ng/ml and above 200ng/ml on day 3 and 7 did not affect ACPR (p = 0.428 and 0.239 respectively) Figure 2.
      Figure 2
      Figure 2Association between lumefantrine plasma concentrations and treatment outcomes.

      Discussion

      Therapeutic efficacy of ALU is highly dependent on adequate systemic bioavailability to the partner drug lumefantrine (
      • Fogg C.
      • Bajunirwe F.
      • Piola P.
      • Biraro S.
      • Checchi F.
      • Kiguli J.
      • Namiiro P.
      • Musabe J.
      • Kyomugisha A.
      • Guthmann J.P.
      Adherence to a six-dose regimen of artemether-lumefantrine for treatment of uncomplicated Plasmodium falciparum malaria in Uganda.
      ;
      • Parikh S.
      • Kajubi R.
      • Huang L.
      • Ssebuliba J.
      • Kiconco S.
      • Gao Q.
      • Li F.
      • Were M.
      • Kakuru A.
      • Achan J.
      Antiretroviral choice for HIV impacts antimalarial exposure and treatment outcomes in Ugandan children.
      ). The present study documents lumefantrine plasma concentrations in routine conditions/ uncontrolled diet intake in the population. A substantial proportion of the patients had day 7 lumefantrine plasma concentration below the cut-off values predicting for treatment failure. Hodel et al performed simulations in a similar population and suggested a substantial proportion of patients would have day 7 lumefantrine concentrations below the cut-off values proposed (
      • Hodel E.M.S.
      • Guidi M.
      • Zanolari B.
      • Mercier T.
      • Duong S.
      • Kabanywanyi A.M.
      • Ariey F.
      • Buclin T.
      • Beck H.-P.
      • Decosterd L.A.
      Population pharmacokinetics of mefloquine, piperaquine and artemether-lumefantrine in Cambodian and Tanzanian malaria patients.
      ). We understand the low levels of lumefantrine concentrations could be due to uncontrolled dietary pattern during the study period unlike in other PK studies, the study focus was on determining plasma concentrations in uncontrolled conditions (real life situation) to reflect what is really happening in the population. An intake of 16g of milk has been shown to increase lumefantrine concentration 6 folds compared to a fasted state (
      • White N.J.
      • van Vugt M.
      • Ezzet F.D.
      Clinical pharmacokinetics and pharmacodynamics of artemether-lumefantrine.
      ). However a small intake of fat (1.2g) has been shown to be associated with adequate lumefantrine exposure (
      • Djimdé A.
      • Lefèvre G.
      Understanding the pharmacokinetics of Coartem®.
      ). Recent studies have suggested the typical african diet is sufficient to archieve adequate lumefantrine exposure (
      • Borrmann S.
      • Sallas W.M.
      • Machevo S.
      • González R.
      • Björkman A.
      • Mårtensson A.
      • Hamel M.
      • Juma E.
      • Peshu J.
      • Ogutu B.
      The effect of food consumption on lumefantrine bioavailability in African children receiving artemether–lumefantrine crushed or dispersible tablets (Coartem®) for acute uncomplicated Plasmodium falciparum malaria.
      ). This study is one of the few studies which have assesed lumefantrine concentrations under real life situation in African population considering a previous study in another area of the country had indicated only 0.4% of malaria patients do take ALU with food despite the empasize given by health care providers that ALU works better if taken with food (
      • Kabanywanyi A.M.
      • Lengeler C.
      • Kasim P.
      • King'eng'ena S.
      • Schlienger R.
      • Mulure N.
      • Genton B.
      Adherence to and acceptability of artemether-lumefantrine as first-line anti-malarial treatment: evidence from a rural community in Tanzania.
      ). It is easy to record high concentrations in controlled PK studies thus showing adequate lumefantrine concentrations but this may be unrealistic because in clinical practice patients receive drugs without control of dietary intake.
      Sex has been suggested to affect pharmacokinetic and pharmacodynamic parameters between men and women for various drugs (
      • Soldin O.P.
      • Chung S.H.
      • Mattison D.R.
      Sex differences in drug disposition.
      ;
      • Whitley H.P.
      • Lindsey W.
      Sex-based differences in drug activity.
      ). The influence of sex on lumefantrine exposure is not well established in humans. In this study, sex influenced both day 3 and 7 lumefantrine concentrations where by males had higher concentrations than females similar to findings reported in malawi (

      TEKETE, M.M., 2020. Day 7 concentration effects of partner drugs of artemisinin and derivatives on recurrent episodes of uncomplicated Plasmodium falciparum malaria after repetitive treatment with the same drug during two years in Mali.

      ). Evidence from animal (rats) study showed higher AUC and bioavailability in males than females (1.66 times higher) possibly due reduced absorption of lumefantrine in female rats (
      • Wahajuddin, Singh S.P.
      • Jain G.K.
      Gender differences in pharmacokinetics of lumefantrine and its metabolite desbutyl-lumefantrine in rats.
      ).
      The present study has also reports a lack of association between age and day 3 and 7 lumefantrine plasma concentrations. Our findings are similar to those reported previously in Thailand (
      • Ezzet F.
      • Van Vugt M.
      • Nosten F.
      • Looareesuwan S.
      • White N.
      Pharmacokinetics and pharmacodynamics of lumefantrine (benflumetol) in acute falciparum malaria.
      ). However, these findings are in contrast with those from other areas (
      • Tchaparian E.
      • Sambol N.C.
      • Arinaitwe E.
      • McCormack S.A.
      • Bigira V.
      • Wanzira H.
      • Muhindo M.
      • Creek D.J.
      • Sukumar N.
      • Blessborn D.
      Population pharmacokinetics and pharmacodynamics of lumefantrine in young Ugandan children treated with artemether-lumefantrine for uncomplicated malaria.
      ;

      TEKETE, M.M., 2020. Day 7 concentration effects of partner drugs of artemisinin and derivatives on recurrent episodes of uncomplicated Plasmodium falciparum malaria after repetitive treatment with the same drug during two years in Mali.

      ). The discrepancy observed may be due to most of children who participated in our study being not very young (above 3 years) since most studies have reported lower day 7 lumefantrine concentrations among very young children than older children and adults (
      • Kloprogge F.
      • Workman L.
      • Borrmann S.
      • Tékété M.
      • Lefèvre G.
      • Hamed K.
      • Piola P.
      • Ursing J.
      • Kofoed P.E.
      • Mårtensson A.
      Artemether-lumefantrine dosing for malaria treatment in young children and pregnant women: a pharmacokinetic-pharmacodynamic meta-analysis.
      ;
      Org W.A.R.N.L.P.P.S.G.k.b.w
      Artemether-lumefantrine treatment of uncomplicated Plasmodium falciparum malaria: a systematic review and meta-analysis of day 7 lumefantrine concentrations and therapeutic response using individual patient data.
      ). Similarily, day 3 lumefantrine concentration was not affected by age contrarily to findings in Uganda (
      • Tchaparian E.
      • Sambol N.C.
      • Arinaitwe E.
      • McCormack S.A.
      • Bigira V.
      • Wanzira H.
      • Muhindo M.
      • Creek D.J.
      • Sukumar N.
      • Blessborn D.
      Population pharmacokinetics and pharmacodynamics of lumefantrine in young Ugandan children treated with artemether-lumefantrine for uncomplicated malaria.
      ), although our findings are in match with another previous study in Uganda (
      • Checchi F.
      • Piola P.
      • Fogg C.
      • Bajunirwe F.
      • Biraro S.
      • Grandesso F.
      • Ruzagira E.
      • Babigumira J.
      • Kigozi I.
      • Kiguli J.
      Supervised versus unsupervised antimalarial treatment with six-dose artemether-lumefantrine: pharmacokinetic and dosage-related findings from a clinical trial in Uganda.
      ). The explanation above on age differences of the study participants may accentuate for the contradiction observed.
      Day 3 lumefantrine plasma concentration is associated with absorption and distribution taking into account the peak lumefantrine concentration after treatment occurs at 70 hours since adminstration, whereas day 7 lumefantrine concentration is suggested to be a result of metabolism and elimination (
      • Checchi F.
      • Piola P.
      • Fogg C.
      • Bajunirwe F.
      • Biraro S.
      • Grandesso F.
      • Ruzagira E.
      • Babigumira J.
      • Kigozi I.
      • Kiguli J.
      Supervised versus unsupervised antimalarial treatment with six-dose artemether-lumefantrine: pharmacokinetic and dosage-related findings from a clinical trial in Uganda.
      ). Day 7 lumefantrine concentrations below cut-off values (175ng/ml & 200ng/ml) were not associated with treatment failure. Our findings are comparable with similar studies in other African populations (
      • Bell D.J.
      • Wootton D.
      • Mukaka M.
      • Montgomery J.
      • Kayange N.
      • Chimpeni P.
      • Hughes D.A.
      • Molyneux M.E.
      • Ward S.A.
      • Winstanley P.A.
      Measurement of adherence, drug concentrations and the effectiveness of artemether-lumefantrine, chlorproguanil-dapsone or sulphadoxine-pyrimethamine in the treatment of uncomplicated malaria in Malawi.
      ;
      • Checchi F.
      • Piola P.
      • Fogg C.
      • Bajunirwe F.
      • Biraro S.
      • Grandesso F.
      • Ruzagira E.
      • Babigumira J.
      • Kigozi I.
      • Kiguli J.
      Supervised versus unsupervised antimalarial treatment with six-dose artemether-lumefantrine: pharmacokinetic and dosage-related findings from a clinical trial in Uganda.
      ;
      • Hodel E.M.S.
      • Guidi M.
      • Zanolari B.
      • Mercier T.
      • Duong S.
      • Kabanywanyi A.M.
      • Ariey F.
      • Buclin T.
      • Beck H.-P.
      • Decosterd L.A.
      Population pharmacokinetics of mefloquine, piperaquine and artemether-lumefantrine in Cambodian and Tanzanian malaria patients.
      ;
      • Kilonzi M.
      • Minzi O.
      • Mutagonda R.
      • Baraka V.
      • Sasi P.
      • Aklillu E.
      • Kamuhabwa A.
      Usefulness of day 7 lumefantrine plasma concentration as a predictor of malaria treatment outcome in under-fives children treated with artemether-lumefantrine in Tanzania.
      ). Studies done in other areas have reported that patients with day 7 lumefantrine levels below 175ng/ml are likely to experience treatment failure than their counterpart contrarily to our findings (
      • Price R.N.
      • Uhlemann A.-C.
      • van Vugt M.
      • Brockman A.
      • Hutagalung R.
      • Nair S.
      • Nash D.
      • Singhasivanon P.
      • Anderson T.J.
      • Krishna S.
      Molecular and pharmacological determinants of the therapeutic response to artemether-lumefantrine in multidrug-resistant Plasmodium falciparum malaria.
      ). The lack of correlation between therapeutic day 7 lumefantrine concentrations (175ng/mL and 200ng/mL) and treatment outcomes suggest that these cut-off values may not be applicable to all regions/populations as documented in Malawi and Northern part of Tanzania (
      • Bell D.J.
      • Wootton D.
      • Mukaka M.
      • Montgomery J.
      • Kayange N.
      • Chimpeni P.
      • Hughes D.A.
      • Molyneux M.E.
      • Ward S.A.
      • Winstanley P.A.
      Measurement of adherence, drug concentrations and the effectiveness of artemether-lumefantrine, chlorproguanil-dapsone or sulphadoxine-pyrimethamine in the treatment of uncomplicated malaria in Malawi.
      ;
      • Kilonzi M.
      • Minzi O.
      • Mutagonda R.
      • Baraka V.
      • Sasi P.
      • Aklillu E.
      • Kamuhabwa A.
      Usefulness of day 7 lumefantrine plasma concentration as a predictor of malaria treatment outcome in under-fives children treated with artemether-lumefantrine in Tanzania.
      ). The lack of predictive effect of the lumefantrine plasma concentrations cut-off values observed in malaria endemic areas may be due to early acquisition of natural immunity against malaria infections unlike to the current concept that children below 5 are naïve. This may be attributed to an increase in frequency of mosquito bites during early childhood. Background immunity acts in synergy with antimalarial chemotherapy in malaria endemic areas (
      • Ezzet F.
      • Van Vugt M.
      • Nosten F.
      • Looareesuwan S.
      • White N.
      Pharmacokinetics and pharmacodynamics of lumefantrine (benflumetol) in acute falciparum malaria.
      ;
      • Kloprogge F.
      • Piola P.
      • Dhorda M.
      • Muwanga S.
      • Turyakira E.
      • Apinan S.
      • Lindegårdh N.
      • Nosten F.
      • Day N.
      • White N.
      Population pharmacokinetics of lumefantrine in pregnant and nonpregnant women with uncomplicated Plasmodium falciparum malaria in Uganda.
      ). The high parasite sensitivity in the studied countries may also account for the lack of correlation between the day 7 plasma concentrations and treatment outcomes observed.
      Few studies have reported day 3 lumefantrine concentration as a strong predictor of treatment failure in young children (
      • Tchaparian E.
      • Sambol N.C.
      • Arinaitwe E.
      • McCormack S.A.
      • Bigira V.
      • Wanzira H.
      • Muhindo M.
      • Creek D.J.
      • Sukumar N.
      • Blessborn D.
      Population pharmacokinetics and pharmacodynamics of lumefantrine in young Ugandan children treated with artemether-lumefantrine for uncomplicated malaria.
      ) and is regarded as a close surrogate predictor of treatment outcomes (
      • Checchi F.
      • Piola P.
      • Fogg C.
      • Bajunirwe F.
      • Biraro S.
      • Grandesso F.
      • Ruzagira E.
      • Babigumira J.
      • Kigozi I.
      • Kiguli J.
      Supervised versus unsupervised antimalarial treatment with six-dose artemether-lumefantrine: pharmacokinetic and dosage-related findings from a clinical trial in Uganda.
      ) than day 7 plasma concentration (
      • Tchaparian E.
      • Sambol N.C.
      • Arinaitwe E.
      • McCormack S.A.
      • Bigira V.
      • Wanzira H.
      • Muhindo M.
      • Creek D.J.
      • Sukumar N.
      • Blessborn D.
      Population pharmacokinetics and pharmacodynamics of lumefantrine in young Ugandan children treated with artemether-lumefantrine for uncomplicated malaria.
      ). The peak lumefantrine concentration is attained approximately 70 hours after the first dose (
      • Ezzet F.
      • Van Vugt M.
      • Nosten F.
      • Looareesuwan S.
      • White N.
      Pharmacokinetics and pharmacodynamics of lumefantrine (benflumetol) in acute falciparum malaria.
      ;
      • White N.J.
      • van Vugt M.
      • Ezzet F.D.
      Clinical pharmacokinetics and pharmacodynamics of artemether-lumefantrine.
      ) thus measuring lumefantrine concentration approximately at 72 hours (day 3) is substantial. Since the day 3 lumefantrine concentration cut-off values predicting treatment failure are inadequately defined, we decided to employ similar cut-off values to day 7 lumefantrine concentration(s) which are widely used. Day 3 lumefantrine concentrations below cut-off values (175ng/ml & 200ng/ml) were not associated with treatment failure. The reasons given for day 7 lumefantrine concentrations may also explain the observed findings above.
      Studies have suggested plasma lumefantrine concentrations are lower in younger children than older children and adults (
      • Barnes K.I.
      • Watkins W.M.
      • White N.J.
      Antimalarial dosing regimens and drug resistance.
      ;
      • Tchaparian E.
      • Sambol N.C.
      • Arinaitwe E.
      • McCormack S.A.
      • Bigira V.
      • Wanzira H.
      • Muhindo M.
      • Creek D.J.
      • Sukumar N.
      • Blessborn D.
      Population pharmacokinetics and pharmacodynamics of lumefantrine in young Ugandan children treated with artemether-lumefantrine for uncomplicated malaria.
      ). Difference in bioavailability of oral administered drugs (which in turn affects plasma concentration) between adults or older children and young children has been attributed to the differences in gastric pH, immaturity of secretion and activity of bile and pancreatic fluid, intestinal transit time and gastric emptying time. Our study has not established a significant difference in lumefantrine plasma levels between adults and children similar to other previous studies. The lack of the difference in lumefantrine exposure between the two age groups could be due to a small number of young children as most of the children in our study were older children. Older children have greater food intake and low vomiting tendency than young children (
      • Borrmann S.
      • Sallas W.M.
      • Machevo S.
      • González R.
      • Björkman A.
      • Mårtensson A.
      • Hamel M.
      • Juma E.
      • Peshu J.
      • Ogutu B.
      The effect of food consumption on lumefantrine bioavailability in African children receiving artemether–lumefantrine crushed or dispersible tablets (Coartem®) for acute uncomplicated Plasmodium falciparum malaria.
      ) which could explain a high absorption compared to young children.
      Although inadequate lumefantrine concentrations (<175ng/ml & <200ng/ml) in real life did not affect treatment outcomes in terms of ACPR and recurrence of parasites at individual level, its contribution to the risk for development of parasite resistance at population level due to the parasite exposure to sub-optimal concentrations cannot be ruled out thus posing a major public health issue.
      Our study has recorded a high proportion of patients with residual lumefantrine concentrations despite patients declaring they had not taken ALU tablets for the past 28 days. Hodel et al recorded similar findings (
      • Hodel E.M.
      • Kabanywanyi A.M.
      • Malila A.
      • Zanolari B.
      • Mercier T.
      • Beck H.-P.
      • Buclin T.
      • Olliaro P.
      • Decosterd L.A.
      • Genton B.
      Residual antimalarials in malaria patients from Tanzania–implications on drug efficacy assessment and spread of parasite resistance.
      ). The presence of low residual lumefantrine concentrations is alarming since exposure of parasites to sub-optimal concentrations may select for resistant parasites. The high proportion of patients with residual lumefantrine concentrations indicates self-medication is common to most patients before coming to hospitals and there is a high drug selection pressure to parasites in the population. Residual drug levels may also expose patients to toxicity upon initiating the treatment. A large proportion of patients with drug concentration prior treatment also suggests that, the patient's history may be not reliable thus there is a need for measuring plasma concentrations at enrollment prior initiation of treatment in antimalaria efficacy studies in malaria endemic regions since the impact of residual plasma concentrations to treatment outcomes is unknown. There may be a need for a modification in the WHO guidelines for antimalarial drugs efficacy surveillance specifically in malaria endemic countries. A similar suggestion was made by
      • Hodel E.M.
      • Kabanywanyi A.M.
      • Malila A.
      • Zanolari B.
      • Mercier T.
      • Beck H.-P.
      • Buclin T.
      • Olliaro P.
      • Decosterd L.A.
      • Genton B.
      Residual antimalarials in malaria patients from Tanzania–implications on drug efficacy assessment and spread of parasite resistance.
      .

      Limitations

      We collected samples on 24 hours basis thus samples between time 0 hours and 24 hours were not collected thus limiting the predictions of absorption related kinetics. Another shortcoming of the present study is unavailability of CYP3A4*1B and CYP3A5*3 data in order to have a pharmacokinetic (PK)/pharmacogenetic (PG) picture. However, our recent review (to be published else where) has established a broader PG/PK picture on antimalarial drugs used for uncomplicated P. falciparum malaria patients in terms of drug exposure, efficacy and safety in Sub-Saharan Africa.

      Conclusion

      Lumefantrine plasma concentrations below cut-off points (175ng/ml and 200ng/ml) on day 3 and 7 did not influence treatment outcomes among uncomplicated malaria patients with uncontrolled dietary intake. Age, sex and level of parasitemia at enrollment did not predict for both day 3 and 7 lumefantrine plasma concentrations.

      Authors’ contributions

      KJM participated in proposal development, sample collection, genotyping of MSP-1 and 2, data analysis and manuscript drafting. ETK, SM and AL carried out data analysis and manuscript reviewing. EK and GS participated in proposal development, supervision of the research group, revising and approving the manuscript for publication.

      Funding

      This work was supported by the Catholic University of Health and Allied Sciences and the National Institute for Medical Research, Mwanza as part of PhD studies.

      Ethical approval and consent to participate

      Ethical and study approval was granted by the joint Catholic University of Health and Allied Sciences (CUHAS) /Bugando Medical Centre (BMC) Institutional Review Board. All patients or parent/guardian signed a written informed consent.

      Consent for publication

      Not applicable.

      Declaration of Competing Interest

      The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. All authors declare no competing interests

      Acknowledgements

      We sincerely thank the participants who donated venous blood and DBS samples throughout the follow up period. We also appreciate the contribution of the nurses, laboratory technicians and clinicians at Karume Health Centre, Igombe Mwanza, Tanzania. We also appreciate the support of the scientists at the department of pharmacology and therapeutics, Makerere University, Uganda.

      References

        • Alessandrini M.
        • Asfaha S.
        • Dodgen T.M.
        • Warnich L.
        • Pepper M.S.
        Cytochrome P450 pharmacogenetics in African populations.
        Drug metabolism reviews. 2013; 45: 253-275
        • Ashley E.A.
        • Stepniewska K.
        • Lindegårdh N.
        • Annerberg A.
        • Kham A.
        • Brockman A.
        • Singhasivanon P.
        • White N.J.
        • Nosten F.
        How much fat is necessary to optimize lumefantrine oral bioavailability?.
        Tropical Medicine & International Health. 2007; 12: 195-200
        • Ashley E.A.
        • Stepniewska K.
        • Lindegårdh N.
        • McGready R.
        • Annerberg A.
        • Hutagalung R.
        • Singtoroj T.
        • Hla G.
        • Brockman A.
        • Proux S.
        Pharmacokinetic study of artemether–lumefantrine given once daily for the treatment of uncomplicated multidrug-resistant falciparum malaria.
        Tropical Medicine & International Health. 2007; 12: 201-208
        • Barnes K.I.
        • Watkins W.M.
        • White N.J.
        Antimalarial dosing regimens and drug resistance.
        Trends in parasitology. 2008; 24: 127-134
        • Bell D.J.
        • Wootton D.
        • Mukaka M.
        • Montgomery J.
        • Kayange N.
        • Chimpeni P.
        • Hughes D.A.
        • Molyneux M.E.
        • Ward S.A.
        • Winstanley P.A.
        Measurement of adherence, drug concentrations and the effectiveness of artemether-lumefantrine, chlorproguanil-dapsone or sulphadoxine-pyrimethamine in the treatment of uncomplicated malaria in Malawi.
        Malaria journal. 2009; 8: 1-11
        • Bolaji O.O.
        • Adehin A.
        • Adeagbo B.A.
        Pharmacogenomics in the Nigerian population: the past, the present and the future.
        Pharmacogenomics. 2019; 20: 915-926
        • Borrmann S.
        • Sallas W.M.
        • Machevo S.
        • González R.
        • Björkman A.
        • Mårtensson A.
        • Hamel M.
        • Juma E.
        • Peshu J.
        • Ogutu B.
        The effect of food consumption on lumefantrine bioavailability in African children receiving artemether–lumefantrine crushed or dispersible tablets (Coartem®) for acute uncomplicated Plasmodium falciparum malaria.
        Tropical Medicine & International Health. 2010; 15: 434-441
        • Campbell M.C.
        • Tishkoff S.A.
        African genetic diversity: implications for human demographic history, modern human origins, and complex disease mapping.
        Annu. Rev. Genomics Hum. Genet. 2008; 9: 403-433
        • Checchi F.
        • Piola P.
        • Fogg C.
        • Bajunirwe F.
        • Biraro S.
        • Grandesso F.
        • Ruzagira E.
        • Babigumira J.
        • Kigozi I.
        • Kiguli J.
        Supervised versus unsupervised antimalarial treatment with six-dose artemether-lumefantrine: pharmacokinetic and dosage-related findings from a clinical trial in Uganda.
        Malaria journal. 2006; 5: 1-8
        • Chotivanich K.
        • Mungthin M.
        • Ruengweerayuth R.
        • Udomsangpetch R.
        • Dondorp A.M.
        • Singhasivanon P.
        • Pukrittayakamee S.
        • White N.J.
        The effects of serum lipids on the in vitro activity of lumefantrine and atovaquone against Plasmodium falciparum.
        Malaria journal. 2012; 11: 1-4
        • Dandara C.
        • Swart M.
        • Mpeta B.
        • Wonkam A.
        • Masimirembwa C.
        Cytochrome P450 pharmacogenetics in African populations: implications for public health.
        Expert opinion on drug metabolism & toxicology. 2014; 10: 769-785
        • Djimdé A.
        • Lefèvre G.
        Understanding the pharmacokinetics of Coartem®.
        Malaria journal. 2009; 8: 1-8
        • El-Shair S.
        • Al Shhab M.
        • Zayed K.
        • Alsmady M.
        • Zihlif M.
        Association Between CYP3A4 and CYP3A5 Genotypes and Cyclosporine's Blood Levels and Doses among Jordanian Kidney Transplanted Patients.
        Current Drug Metabolism. 2019; 20: 682-694
        • Eng H.-S.
        • Mohamed Z.
        • Calne R.
        • Lang C.
        • Mohd M.
        • Seet W.-T.
        • Tan S.-Y.
        The influence of CYP3A gene polymorphisms on cyclosporine dose requirement in renal allograft recipients.
        Kidney international. 2006; 69: 1858-1864
        • Ezzet F.
        • Mull R.
        • Karbwang J.
        Population pharmacokinetics and therapeutic response of CGP 56697 (artemether+ benflumetol) in malaria patients.
        British journal of clinical pharmacology. 1998; 46: 553-561
        • Ezzet F.
        • Van Vugt M.
        • Nosten F.
        • Looareesuwan S.
        • White N.
        Pharmacokinetics and pharmacodynamics of lumefantrine (benflumetol) in acute falciparum malaria.
        Antimicrobial agents and chemotherapy. 2000; 44: 697-704
        • Fogg C.
        • Bajunirwe F.
        • Piola P.
        • Biraro S.
        • Checchi F.
        • Kiguli J.
        • Namiiro P.
        • Musabe J.
        • Kyomugisha A.
        • Guthmann J.P.
        Adherence to a six-dose regimen of artemether-lumefantrine for treatment of uncomplicated Plasmodium falciparum malaria in Uganda.
        Am J Trop Med Hyg. 2004; 71: 525-530
        • Hodel E.M.
        • Kabanywanyi A.M.
        • Malila A.
        • Zanolari B.
        • Mercier T.
        • Beck H.-P.
        • Buclin T.
        • Olliaro P.
        • Decosterd L.A.
        • Genton B.
        Residual antimalarials in malaria patients from Tanzania–implications on drug efficacy assessment and spread of parasite resistance.
        PLoS One. 2009; 4: e8184
        • Hodel E.M.S.
        • Guidi M.
        • Zanolari B.
        • Mercier T.
        • Duong S.
        • Kabanywanyi A.M.
        • Ariey F.
        • Buclin T.
        • Beck H.-P.
        • Decosterd L.A.
        Population pharmacokinetics of mefloquine, piperaquine and artemether-lumefantrine in Cambodian and Tanzanian malaria patients.
        Malaria journal. 2013; 12: 1-17
        • Kabanywanyi A.M.
        • Lengeler C.
        • Kasim P.
        • King'eng'ena S.
        • Schlienger R.
        • Mulure N.
        • Genton B.
        Adherence to and acceptability of artemether-lumefantrine as first-line anti-malarial treatment: evidence from a rural community in Tanzania.
        Malaria journal. 2010; 9: 1-7
        • Kampira E.
        • Kumwenda J.
        • J van Oosterhout J.
        • Chaponda M.
        • Dandara C.
        Pharmacogenetics research developments in Africa: a focus on Malawi.
        Current Pharmacogenomics and Personalized Medicine (Formerly Current Pharmacogenomics). 2012; 10: 87-97
        • Keshava C.
        • McCanlies E.C.
        • Weston A.
        CYP3A4 polymorphisms—potential risk factors for breast and prostate cancer: a HuGE review.
        American journal of epidemiology. 2004; 160: 825-841
        • Khuda F.
        • Iqbal Z.
        • Shah Y.
        • Ahmmad L.
        • Nasir F.
        • Khan A.Z.
        • Shahbaz N.
        Method development and validation for simultaneous determination of lumefantrine and its major metabolite, desbutyl lumefantrine in human plasma using RP-HPLC/UV detection.
        Journal of chromatography B. 2014; 944: 114-122
        • Kilonzi M.
        • Minzi O.
        • Mutagonda R.
        • Baraka V.
        • Sasi P.
        • Aklillu E.
        • Kamuhabwa A.
        Usefulness of day 7 lumefantrine plasma concentration as a predictor of malaria treatment outcome in under-fives children treated with artemether-lumefantrine in Tanzania.
        Malaria journal. 2020; 19: 1-8
        • Kloprogge F.
        • McGready R.
        • Hanpithakpong W.
        • Blessborn D.
        • Day N.P.
        • White N.J.
        • Nosten F.
        • Tarning J.
        Lumefantrine and desbutyl-lumefantrine population pharmacokinetic-pharmacodynamic relationships in pregnant women with uncomplicated Plasmodium falciparum malaria on the Thailand-Myanmar border.
        Antimicrobial agents and chemotherapy. 2015; 59: 6375-6384
        • Kloprogge F.
        • Piola P.
        • Dhorda M.
        • Muwanga S.
        • Turyakira E.
        • Apinan S.
        • Lindegårdh N.
        • Nosten F.
        • Day N.
        • White N.
        Population pharmacokinetics of lumefantrine in pregnant and nonpregnant women with uncomplicated Plasmodium falciparum malaria in Uganda.
        CPT: pharmacometrics & systems pharmacology. 2013; 2: 1-10
        • Kloprogge F.
        • Workman L.
        • Borrmann S.
        • Tékété M.
        • Lefèvre G.
        • Hamed K.
        • Piola P.
        • Ursing J.
        • Kofoed P.E.
        • Mårtensson A.
        Artemether-lumefantrine dosing for malaria treatment in young children and pregnant women: a pharmacokinetic-pharmacodynamic meta-analysis.
        PLoS medicine. 2018; 15e1002579
        • Obua C.
        • Hellgren U.
        • Ntale M.
        • Gustafsson L.L.
        • Ogwal-Okeng J.W.
        • Gordi T.
        • Jerling M.
        Population pharmacokinetics of chloroquine and sulfadoxine and treatment response in children with malaria: suggestions for an improved dose regimen.
        British journal of clinical pharmacology. 2008; 65: 493-501
        • Org W.A.R.N.L.P.P.S.G.k.b.w
        Artemether-lumefantrine treatment of uncomplicated Plasmodium falciparum malaria: a systematic review and meta-analysis of day 7 lumefantrine concentrations and therapeutic response using individual patient data.
        BMC medicine. 2015; 13: 1-19
        • Organization W.H.
        Methods and techniques for clinical trials on antimalarial drug efficacy: genotyping to identify parasite populations: informal consultation organized by the Medicines for Malaria Venture and cosponsored by the World Health Organization.
        World Health Organization, Amsterdam, The Netherlands2008 (29-31 May 2007)
        • Organization W.H.
        Basic malaria microscopy: Part I. Learner's guide.
        World Health Organization, 2010
        • Organization W.H.
        Guidelines for the treatment of malaria.
        World Health Organization, 2015
      1. Organization, W.H., 2015b. Methods for surveillance of antimalarial drug efficacy. 2009.

        • Organization W.H.
        World malaria report 2015.
        World Health Organization, 2016
        • Pang K.S.
        Modeling of intestinal drug absorption: roles of transporters and metabolic enzymes (for the Gillette Review Series).
        Drug metabolism and disposition. 2003; 31: 1507-1519
        • Parikh S.
        • Kajubi R.
        • Huang L.
        • Ssebuliba J.
        • Kiconco S.
        • Gao Q.
        • Li F.
        • Were M.
        • Kakuru A.
        • Achan J.
        Antiretroviral choice for HIV impacts antimalarial exposure and treatment outcomes in Ugandan children.
        Reviews of Infectious Diseases. 2016; 63: 414-422
        • Piedade R.
        • Gil J.P.
        The pharmacogenetics of antimalaria artemisinin combination therapy.
        Expert Opin Drug Metab Toxicol. 2011; 7: 1185-1200
        • Pillai G.
        • Davies G.
        • Denti P.
        • Steimer J.L.
        • McIlleron H.
        • Zvada S.
        • Chigutsa E.
        • Ngaimisi E.
        • Mirza F.
        • Tadmor B.
        Pharmacometrics: opportunity for reducing disease burden in the developing world: the case of Africa.
        CPT: Pharmacometrics & Systems Pharmacology. 2013; 2: 1-4
        • Price R.N.
        • Uhlemann A.-C.
        • van Vugt M.
        • Brockman A.
        • Hutagalung R.
        • Nair S.
        • Nash D.
        • Singhasivanon P.
        • Anderson T.J.
        • Krishna S.
        Molecular and pharmacological determinants of the therapeutic response to artemether-lumefantrine in multidrug-resistant Plasmodium falciparum malaria.
        Clinical Infectious Diseases. 2006; 42: 1570-1577
        • Soldin O.P.
        • Chung S.H.
        • Mattison D.R.
        Sex differences in drug disposition.
        Journal of Biomedicine and Biotechnology 2011. 2011;
        • Somé A.F.
        • Bazié T.
        • Zongo I.
        • Yerbanga R.S.
        • Nikiéma F.
        • Neya C.
        • Taho L.K.
        • Ouédraogo J.-B.
        Plasmodium falciparum msp 1 and msp 2 genetic diversity and allele frequencies in parasites isolated from symptomatic malaria patients in Bobo-Dioulasso.
        Parasites & vectors. 2018; 11 (Burkina Faso): 1-8
        • Staehli Hodel E.M.
        • Csajka C.
        • Ariey F.
        • Guidi M.
        • Kabanywanyi A.M.
        • Duong S.
        • Decosterd L.A.
        • Olliaro P.
        • Beck H.P.
        • Genton B.
        Effect of single nucleotide polymorphisms in cytochrome P450 isoenzyme and N-acetyltransferase 2 genes on the metabolism of artemisinin-based combination therapies in malaria patients from Cambodia and Tanzania.
        Antimicrob Agents Chemother. 2013; 57: 950-958
        • Tang H.-L.
        • Ma L.-L.
        • Xie H.-G.
        • Zhang T.
        • Hu Y.-F.
        Effects of the CYP3A5* 3 variant on cyclosporine exposure and acute rejection rate in renal transplant patients: a meta-analysis.
        Pharmacogenetics and genomics. 2010; 20: 525-531
        • Tchaparian E.
        • Sambol N.C.
        • Arinaitwe E.
        • McCormack S.A.
        • Bigira V.
        • Wanzira H.
        • Muhindo M.
        • Creek D.J.
        • Sukumar N.
        • Blessborn D.
        Population pharmacokinetics and pharmacodynamics of lumefantrine in young Ugandan children treated with artemether-lumefantrine for uncomplicated malaria.
        The Journal of infectious diseases. 2016; 214: 1243-1251
      2. TEKETE, M.M., 2020. Day 7 concentration effects of partner drugs of artemisinin and derivatives on recurrent episodes of uncomplicated Plasmodium falciparum malaria after repetitive treatment with the same drug during two years in Mali.

        • Wahajuddin, Singh S.P.
        • Jain G.K.
        Gender differences in pharmacokinetics of lumefantrine and its metabolite desbutyl-lumefantrine in rats.
        Biopharmaceutics & drug disposition. 2012; 33: 229-234
        • White N.J.
        • Stepniewska K.
        • Barnes K.
        • Price R.N.
        • Simpson J.
        Simplified antimalarial therapeutic monitoring: using the day-7 drug level?.
        Trends in parasitology. 2008; 24: 159-163
        • White N.J.
        • van Vugt M.
        • Ezzet F.D.
        Clinical pharmacokinetics and pharmacodynamics of artemether-lumefantrine.
        Clinical pharmacokinetics. 1999; 37: 105-125
        • Whitley H.P.
        • Lindsey W.
        Sex-based differences in drug activity.
        American family physician. 2009; 80: 1254-1258