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Objectives: This study assessed the activity of thiopurine S-methyltransferase (TPMT) in Nigerians with a view to providing data on susceptibility to thiopurine toxicity, and as well generate reference activity values for clinical use. Results: TPMT activity, expressed as the amount of 6MMP in ng/mL after 1 h incubation at 37 °C per haemoglobin (U/g Hb), varied between 2.34 and 63.50 U/g Hb in the study population. Poor metabolic phenotypes, characterised by an activity values below 8.41 U/g Hb, were observed in 20% of the study subjects. Intermediate metabolizers had activity values between 8.41 and 16.13 U/g Hb. Fast and very fast metabolizers were characterised by activity values of 16.20-56.22 and > 56.22 U/g Hb, respectively. These findings suggest that a potentially huge discordance between TPMT phenotype and genotype exist in Nigerians, and emphasizes the superiority of a prior determination of TPMT metabolic phenotype in ensuring the safety of thiopurine drug administration in the population. [ABSTRACT FROM AUTHOR]

Introduction Thiopurine S-methyltransferase (TPMT) methylates clinically relevant thiopurine drugs most of which are noted for adverse reactions in certain users, largely due to polymorphisms in the TPMT gene. Aim This study investigated the prevalence of functionally relevant TPMT alleles in the Nigerian population. Material and methods One hundred eighty unrelated subjects consisting of 123 males and 57 females from the main Nigerian ethnicities (44 Igbo, 101 Yoruba, 23 Hausa and 12 from other minor ethnic groups) were genotyped for TPMT*2 , *3B , *3C and *4 alleles using the iPLEX genotyping assay technique. The genotype calls were validated with Sanger sequencing in a random set of samples and the acquired data were assessed for Hardy–Weinberg equilibrium using the Fisher's exact test. Results and discussion Defective TMPT alleles were found in individuals representing 10% of the study population. TPMT*3C constituted 9.4% (95% CI, 5.6–14.7) of all alleles detected, with one homozygote and 17 heterozygotes recorded. The prevalence of the TPMT*3C allele in the population conformed with Hardy–Weinberg equilibrium. TPMT*2 , 3B and *4 were, however, not detected in the population. Conclusions TPMT*3C was the only defective allele identified in Nigerians and may hence be the major underlying genetic contributor to adverse reactions due to thiopurine drugs in the population. [ABSTRACT FROM AUTHOR]

Objectives: This manuscript describes the development, validation and clinical application of a novel method for the quantification of the antiretroviral drug efavirenz in dried breast milk spots using LC-MS.Methods: Dried breast milk spots were prepared by spotting 30 μL of human breast milk on each circle of Whatman 903 Protein Saver cards. Chromatographic separation was achieved on a reverse-phase C18 column with 1 mM ammonium acetate in water/acetonitrile using a solvent gradient at a flow rate of 400 μL/min and detection was by TSQ Quantum Access triple quadrupole mass spectrometer equipped with a heated electrospray ionization source. The method was applied to characterize the breast milk pharmacokinetic profile of efavirenz in HIV-positive nursing mothers receiving regimens containing 600 mg of efavirenz once daily.Results: The assay was validated over the concentration range 50-7500 ng/mL. Accuracy ranged between 95.2% and 102.5% and precision ranged between 1.05% and 9.53%. The average recovery of efavirenz from dried breast milk spots was 106.4% and the matrix effect was 8.14%. Stability of efavirenz in dried breast milk spots and processed samples at room temperature, -40°C and -80°C was demonstrated. In the pharmacokinetic study, the mean (SD) AUC0-24, Cmax and Cmin of efavirenz in breast milk were 59,620 ng·h/mL (17,440), 4527 ng/mL (1767) and 1261 ng/mL (755.9), respectively. The mean (range) milk-to-plasma concentration ratio over the dosing interval was 0.78 (0.57-1.26).Conclusions: The dried breast milk spot method is simple, robust, accurate and precise, and can be used in settings with limited resources. [ABSTRACT FROM AUTHOR]

Objective: To examine the possibility of a different extent of chloroquine (CQ) metabolism in human pregnancy by determining blood level profiles of the drug and its major metabolite, desethylchloroquine (CQM).Methods: Five women in the early third trimester of pregnancy and five non-pregnant women received each a single 600 mg oral dose of CQ and blood samples were collected at pre-determined intervals following drug administration. Plasma concentrations of CQ and CQM were analysed by an established HPLC method.Results: The C(max) and AUC(0-48 h) of CQM were significantly higher in the pregnant than the non-pregnant group (P = 0.009). The ratio AUC(CQ)/AUC(CQM) ranged from 0.09 to 0.35 among pregnant women, and from 1.70 to 4.81 among non-pregnant women.Conclusion: Results from this preliminary study indicate an occurrence of induction of metabolism of CQ in the early third trimester of pregnancy. In view of toxicological importance of CQ metabolites, it is suggested that caution should be exercised in evaluation of higher dosage regimen of CQ in pregnant women. [ABSTRACT FROM AUTHOR]

Background: In Nigeria, since 2002, Imatinib mesylate (glivec®) has been available freely to chronic myeloid leukaemia (CML) patients but only at a tertiary health care centre in the southwestern part of the country. Despite this, it is not readily accessible to many patients due to the distance and other challenges including low socioeconomic status and political problems, preventing timely access to specialist care. This study evaluated the effect of the baseline characteristics on the prognostic implication and treatment outcome of CML patients in Nigeria. Method: This study retrospectively evaluated the baseline characteristics, clinical presentations and treatment outcomes of 889 CML patients over 18 years (2002–2020). Of these, 576 (65%) patients had complete information with up-to-date BCR::ABL1 records. These 576 patients were categorized based on their responses to Imatinib therapy into three groups viz.; Optimal response (OR) defined as BCR::ABL1 ratio of < 0.1% or major molecular remission (≥ 3-log reduction of BCR::ABL1 mRNA or BCR::ABL1 ratio of < 0.1% on the International Scale), Suboptimal response (SR) with BCR::ABL ratio of 0.1–1%, and Treatment failure (TF) when MMR has not been achieved at 12 months. The variables were analyzed using descriptive and inferential statistics and a p-value < 0.05 was considered statistically significant. Results: The result revealed a median age of 37 years at diagnosis with a male-to-female ratio of 1.5:1. The majority (96.8%) of the patients presented with one or more symptoms at diagnosis with a mean symptom duration of 12 ± 10.6 months. The mean Sokal and EUTOS scores were 1.3 ± 0.8 and 73.90 ± 49.09 respectively. About half of the patients presented with high-risk Sokal (49%) and EUTOS (47%) scores. Interestingly, both the Sokal (r = 0.733, p = 0.011) and EUTOS (r = 0.102, p = 0.003) scores correlated positively and significantly with the duration of symptoms at presentation. Based on response categorization, 40.3% had OR while 27.1% and 32.6% had SR and TF respectively. Conclusion: This study observed a low optimal response rate of 40.3% and treatment failure rate of 32.6% in our CML cohort while on first-line Imatinib therapy. This treatment response is strongly attributable to the long duration of symptoms of 12 months or more and high Sokal and EUTOS scores at presentation. We advocate prompt and improved access to specialist care with optimization of tyrosine kinase inhibitor therapy in Nigeria. [ABSTRACT FROM AUTHOR]

Context: Co-administration of amodiaquine with MAMA decoction (MD), an herbal antimalarial drug comprising the leaves ofMangifera indicaL. (Anacardiaceae), Alstonia booneiDe Wild (Apocynaceae), Morinda lucidaBenth (Rubiaceae) andAzadirachta indicaA. Juss (Meliaceae) was investigated. The practice of concurrent administration of herbal medicines with orthodox drugs is currently on the increase globally. Objective: The study was designed to investigate the possible enhancement of the antimalarial potency as well as possible herb–drug interaction resulting from concurrent administration of MAMA decoction with amodiaquine (AQ). Materials and methods: Combinations of MD with AQ were investigated in chloroquine (CQ)-sensitivePlasmodium bergheiNK 65 in varying oral doses (mg/kg) at: sub-therapeutic [MD30 + AQ1.25], therapeutic [MD120 + AQ10] and median effective [MD40 + AQ3.8], using chemosuppressive and curative antimalarial test models. Secondly,P. bergheiANKA (CQ-resistant)-infected mice were orally treated with MD 120, 240, [MD120 + AQ10] and [MD240 + AQ10] mg/kg, using both models. The survival times of mice were monitored for 28 d. Results: ED50values of MD and AQ were 48.8 and 4.1 mg/kg, respectively. A total parasite clearance of CQ-sensitiveP. bergheiNK65 was obtained with the therapeutic combination dose in the curative test giving an enhanced survival time. In CQ-resistantP. bergheiANKA-infected mice, [MD120 + AQ10] and [MD240 + AQ10] mg/kg gave comparable activities with AQ (10 mg/kg) in both models. Conclusion: The therapeutic combination dose gave total parasite clearance of CQ-sensitiveP. bergheiNK65, whereas none of the doses tested showed notable activity against CQ-resistantP. bergheiANKA. [ABSTRACT FROM PUBLISHER]

Background: Malaria is a major public health issue with substantial risks among vulnerable populations. Currently, the World Health Organization (WHO) recommends SP-IPTp in the second and third trimesters. However, the efficacy of SP-IPTp is threatened by the emergence of sulfadoxine-pyrimethamine resistant malaria parasites due to single nucleotide polymorphisms in the Plasmodium falciparum dihydrofolate reductase and dihydropteroate synthetase genes. This study aimed to assess the current prevalence of Pfdhfr/Pfdhps mutations in P. falciparum isolates collected from individuals residing in Ile-Ife, Nigeria, and also present maps of the prevalence of Pfdhps 431V and 581G within Nigeria and surrounding countries. Methods: Between October 2020 and April 2021, samples were collected as dried blood spots among 188 participants who showed malaria positivity with a histidine-rich-protein-based rapid diagnostic test (RDT). Nested PCR assays were used to confirm falciparum in the samples with RDT positivity, and to amplify fragments of the Pfdhfr/Pfdhps genes followed by targeted amplicon sequencing. Published data since 2007 on the prevalence of the Pfdhps genotypes in Nigeria and the neighbouring countries were used to produce maps to show the distribution of the mutant genotypes. Results: Only 74 and 61 samples were successfully amplified for the Pfdhfr and Pfdhps genes, respectively. At codons resulting in N51I, C59R, and S108N, Pfdhfr carried mutant alleles of 97.3% (72/74), 97.3% (72/74) and 98.6% (73/74), respectively. The Pfdhps gene carried mutations at codons resulting in amino acid changes at 431–436-437–540-581–613; I431V [45.9%, (28/61)], A581G [31.1% (19/61)] and A613S [49.2% (30/61)]. Constructed haplotypes were mainly the triple Pfdhfr mutant 51I-59R-108N (95.9%), and the most common haplotypes observed for the Pfdhps gene were the ISGKAA (32.8%), ISGKGS (8.2%), VAGKAA (14.8%), VAGKAS (9.8%) and VAGKGS (14.8%). In the context of the previously published data, a high prevalence of 431V/581G mutations was found in the study population. It seems quite evident that the Pfdhps 431V, 581G and 613S often co-occur as Pfdhps-VAGKGS haplotype. Conclusion: This study showed that the prevalence of VAGKGS haplotype seems to be increasing in prevalence. If this is similar in effect to the emergence of 581G in East Africa, the efficacy of SP-IPTp in the presence of these novel Pfdhps mutants should be re-assessed. [ABSTRACT FROM AUTHOR]

Purpose: To develop a simple, sensitive and selective method for the determination of dextromethorphan and its metabolite, dextrophan in human urine using reversed-phase high performance liquid chromatography with UV-spectrophotometric detection (RP-HPLC-UV). Methods: Pre-column sample clean-up was carried out by liquid-liquid extraction of the analytes with chloroform: isopropanol (70:30) solution after alkalization of 1000 µL sample and spiking of internal standard, morphine. The samples were chromatographed in a reversed-phase (C-18) ultra sphere silica (5µm particle size and 250 x 4.6 mm I.D). The mobile phase consisted of methanol: acetonitrile: 0.5% w/v ammonium acetate (10:10:80) adjusted to pH 2.8 with orthophosphoric acid and pumped through the column at 1ml/min flow rate. The analytical method was validated for accuracy and precision as well as the recovery of the analytes, dextromethorphan and its metabolite, dextrophan over the concentration range of 0.20 to 5.0µg/ml. Results: The standard curves were linear over the concentration range of 0.2 to 5.0µg/ml for dextromethorphan and dextrorphan. The regression coefficients (R²) of the analytes were >0.99. The method was reproducible with coefficient of variation for the analytes being < 10 %. Dextromethorphan was well resolved from its metabolite, dextrorphan and the internal standard, morphine. The limits of detection of dextromethorphan and dextrorphan were 50ng/ml and the recoveries and accuracies were greater than 85 and 90 %, respectively. Conclusion: The analytical assay method exhibits good precision and selectivity and it was applied to the analysis of dextromethorphan and dextrorphan in urine for the assessment of CYP2D6 activity. [ABSTRACT FROM AUTHOR]

• Varied disposition imparts on the tolerance and safety of quinine, and thus constitutes a major limiting consideration for its dosing in uncomplicated malaria. Utilizing a population approach, the effect of body weight and infection status on disposition parameters of quinine were evaluated in Nigerian subjects. • A reversal of infection-induced changes in volume of distribution and clearance after 48 h of chronic quinine administration was noted. • It is hypothesized that a downward review of quinine regimen post-48 h of chronic administration, in the event of complete parasitaemia clearance, might be a useful approach in enhancing tolerance and safety. The varied disposition of the antimalarial quinine partly explains its poor tolerance and toxicity in humans. Using a population approach, the disposition of quinine in healthy subjects and patients with acute uncomplicated symptomatic malaria from Nigeria was re-examined with a view to providing population-specific attributes. Concentration versus time profiles of quinine over 48 hours in healthy individuals, and over 7 days in malaria-infected patients, were stratified to reflect: concentration versus time data during the first 48 hours of quinine administration for healthy subjects and infected patients, concentration versus time data after 48 hours in infected patients, and all concentration versus time data available for healthy subjects and infected patients. Pharmacokinetic parameters were then estimated with a stochastic approximation expectation maximization algorithm. All datasets were fitted by a 1-compartment model with covariate contributions from body weight and infection status. The absorption rate constant, and volume of distribution and clearance were 1.72 h–1, 86.8 to 157.4 L, and 6.6 to 9.6 L/h, respectively. Infected patients experienced a 38% decrease in volume of distribution and a 31% decrease in clearance in the first 48 hours relative to healthy individuals. The contraction in volume of distribution and clearance diminished significantly after 48 hours of chronic quinine dosing in infected patients. The study findings suggest that clinical interventions aimed at enhancing the safety and tolerance of quinine might be achieved by a rational decrease in dose size and/or dosing interval, post-48 hours of chronic quinine administration, in malaria-infected patients. [ABSTRACT FROM AUTHOR]

Imatinib has been successful in the management of chronic myeloid leukemia (CML) but some patients experience adverse reactions or develop resistance to its use. The roles of some polymorphisms in genes encoding enzymes critical for the biotransformation of imatinib have been previously examined. This study, hence, evaluated some other unstudied functionally significant polymorphisms in CYP1A2, CYP2C8, CYP2C9, and CYP3A5. Trough imatinib blood levels and genotypes were determined in 42 CML patients by an HPLC-UV technique and a Sequenom iPLEX assay, respectively. Statistical analysis of the influence of genetic polymorphisms on standardized trough level detected no significant relationship. However, higher trough levels were observed in two homozygous carriers of CYP2C8*2 while diminished imatinib levels were seen in two homozygous carriers of CYP3A5*7. The study findings suggest that polymorphisms in drug metabolizing enzymes may be significant for imatinib therapy only in instances where all copies of the relevant studied genes are functionally impaired. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented about the pharmacogenetics research among African populations.