Babatunde A. Adeagbo

Development, validation and clinical application of a novel method for the quantification of efavirenz in dried breast milk spots using LC-MS/MS

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.

Influence of CYP3A5*3 and ABCB1 C3435T on clinical outcomes and trough plasma concentrations of imatinib in Nigerians with chronic myeloid leukaemia.

Imatinib mesylate is the first‐line drug for the treatment of Philadelphia/bcr‐abl positive chronic myeloid leukaemia (CML). It is known to be metabolized mostly by CYP3A4 and CYP3A5 isoforms while its efflux is mediated by the transporters ABCB1 and ABCG2. Genetic polymorphism of some of these enzymes and transporters have been linked with inter‐individual variations in the pharmacokinetics of the drug. This study, therefore, investigated the influence of CYP3A5*3, ABCG2 421C>A and ABCB1 3435 C>T genetic polymorphism on the clinical outcome and steady‐state trough plasma concentration (TPC) of imatinib in Nigerians with CML.

Simple HPLC-UV Method for Pharmacokinetic Studies of Imatinib in the Presence of Common Antimalaria Agents

Imatinib mesylate is currently the drug of choice for treatment of chronic myeloid leukaemia. There is great possibility of coadministration of this drug with antimalaria agents in malaria-endemic regions of the world. The need, therefore, arises to develop a sensitive, simple, and reliable HPLC method that could determine imatinib in human plasma in the presence of these common antimalaria agents. After protein precipitation with acetonitrile and centrifugation, the sample was subjected to isocratic elution on an Agilent Zorbax SB-Cyano column with a mobile phase consisting of methanol-phosphate buffer (0.1 M, adjusted to pH 3 with perchloric acid) (60:40%, v/v) at a flow rate of 1 ml/min and monitored at 267 nm. The method was found to be specific in determining imatinib in plasma in the presence of amodiaquine, chloroquine, proguanil, quinine, artesunate, artemether, and lumefantrine. The standard curve for imatinib was linear over the concentration range of 10–2000 ng/mL (r > 0.999) with improved recovery in the range of 96.5–98.5%. The inter- and intra-day precisions, expressed as % coefficient of variation (% CV), were lower than 10% in all the concentration levels tested, whereas assay accuracy was in the range of 97.26–109.3%. The method was used to estimate pharmacokinetic parameters of imatinib in three imatinib-naïve patients.

Alteration of the Disposition of Quinine in Healthy Volunteers After Concurrent Ciprofloxacin Administration.

This study evaluated the effects of concurrent ciprofloxacin administration on the disposition of quinine in healthy volunteers. Quinine (600-mg single dose) was administered either alone or with the 11th dose of ciprofloxacin (500 mg every 12 hours for 7 days) to 15 healthy volunteers in a crossover fashion. Blood samples collected at predetermined time intervals were analyzed for quinine and its major metabolite, 3-hydroxquinine, using a validated high-performance liquid chromatographic method. Administration of quinine plus ciprofloxacin resulted in significant increases (P < 0.05) in the total area under the concentration–time curve, maximum plasma concentration (Cmax), and terminal elimination half-life (T1/2b) of quinine compared with values with quinine dosing alone (AUC: 27.93 ± 8.04 vs. 41.62 ± 13.98 h·mg/L; Cmax: 1.37 ± 0.24 vs. 1.64 ± 0.38 mg/L; T1/2b: 16.28 ± 2.66 vs. 21.43 ± 3.22 hours), whereas the oral plasma clearance markedly decreased (23.17 ± 6.49 vs. 16.00 ± 5.27 L/h). In the presence of ciprofloxacin, there was a pronounced decrease in the ratio of AUC (metabolite)/AUC (unchanged drug) and highly significant decreases in Cmax and AUC of the metabolite (P < 0.05). Ciprofloxacin may increase the adverse effects of concomitantly administered quinine, which can have serious consequences on the patient. Thus, a downward dosage adjustment of quinine seems to be necessary when concurrently administered with ciprofloxacin.

Quality of artemisinin-based antimalarial drugs marketed in Nigeria

Background Artemisinin combination therapy is first-line therapy for treatment of malaria, which is one of the most significant public health problems in Nigeria. With the increasing level of use of these drugs coupled with the emergence of resistance, there is a need for regular post-market surveillance. Method Twenty different brands of artesunate-containing antimalarial drugs and 10 brands of artemether-lumefantrine were multi-sourced in the south western part of Nigeria and were subjected to identification, weight uniformity test, and assay using United State pharmacopoeia and International Pharmacopoeia monographs. In vitro-dissolution test of the artemether tablets was also investigated. Results All 10 brands (100%) of the artemether-lumefantrine tablets met the assay requirement for artemether and 8 (80%) met the assay requirement for lumefantrine, but only 4 brands (40%) met the requirement for artemether dissolution. One of these brands failed the weight uniformity test. Of the 20 brands of artesunate-containing brands included in this study, 15 (75%) met the standard assay requirement for artesunate and two failed the weight uniformity test. Conclusions There is evidence of the presence of substandard artemisinin products in the Nigerian market.

Population Pharmacokinetics of Imatinib in Nigerians With Chronic Myeloid Leukemia: Clinical Implications for Dosing and Resistance

Imatinib, a tyrosine kinase inhibitor, is the drug of choice for the treatment of chronic myeloid leukemia in Nigeria. Several studies have established interindividual and interpopulation variations in imatinib disposition although no pharmacokinetic study have been conducted in an African population since the introduction of the drug. This study explored a population pharmacokinetic approach to investigate the disposition of imatinib in Nigerians and examined the involvement of some covariates including genetic factors in the variability of the drug disposition with a view to optimize the use of the drug in this population. A total of 250 plasma concentrations from 126 chronic myeloid leukemia patients were quantified using a validated method. A population pharmacokinetic model was fitted to the data using NONMEM VII software, and the influences of 12 covariates were investigated. The mean population‐derived apparent steady‐state clearance, elimination half‐life, area under the concentration‐time curve over 24 hours, and volume of distribution were 17.2 ± 1.8 L/h., 12.05 ± 2.1 hours, 23.26 ± 0.6 μg·h/mL, and 299 ± 20.4 L, respectively. Whole blood count, ethnicity, CYP3A5*3, and ABCB1 C3435T were found to have significant influence on the apparent clearance, while the interindividual variability in clearance and interoccasion variability in bioavailability were 17.4% and 20.4%, respectively. There was a wide variability in apparent clearance and area under the curve compared to those reported in other populations. Thus, treatment with a standard dose of imatinib in this population may not produce the desired effect in most of the patients, whereas continuous exposure to a low drug concentration could lead to pharmacokinetic‐derived resistance. The authors suggest the need for therapeutic drug monitoring–guided dose individualization in this population.

Simultaneous determination of amodiaquine and pioglitazone on dried blood spots (DBS) by HPLC–DAD and its usefulness in pharmacokinetic studies

ABSTRACT A simple and rapid method for simultaneous determination of amodiaquine and pioglitazone in dried blood spots (DBS) was developed and validated. Blood samples were spotted on protein saver cards and dried and a 4-mm punch was extracted with methanol first and later with 1% acetic acid and dichloromethane. The separation was achieved on a C8 Zorbax Eclipse XDB analytical column (4 µm, 150 × 4.6 mm2 i.d.) at 27°C with a mobile phase of methanol/0.2% acetic acid (60:40) at a flow rate of 0.8 mL/min and detected at 230 nm. The method was linear over the range 2–80 ng/mL for amodiaquine and 10–1500 ng/mL for pioglitazone with correlation coefficients greater than 0.9995. The limits of detection were 1.12 and 10.93 µg/L and the limits of quantification were 3.39 and 33.11 µg/L for amodiaquine and pioglitazone, respectively. The inter- and intra-day precision were <6.7 and <7% for amodiaquine and <6.3 and <3% for pioglitazone. The method was applied to estimate the pharmacokinetic (PK) parameters in four healthy volunteers and it was found to yield identical PK profiles with other earlier methods supporting the use of DBS as an alternative for PK study. GRAPHICAL ABSTRACT

Bidirectional Pharmacokinetic Interaction Between Amodiaquine and Pioglitazone in Healthy Subjects

Amodiaquine (AQ) and pioglitazone (PGZ) are both metabolized by CYP2C8, an enzyme also inhibited by PGZ. These drugs are likely to be administered in instances of comorbidity of malaria with type 2 diabetes. This study, hence, evaluated the possibility of a drug interaction resulting from the concurrent use of both drugs. A 3‐period crossover design in 10 healthy subjects, that assessed the disposition of AQ and PGZ alone and when coadministered, was implemented with the administration of single oral doses of AQ and PGZ. Whole‐blood samples collected between 0 and 24 hours on protein saver cards across the study periods were processed and analyzed for AQ and PGZ contents. Pharmacokinetic parameters were derived by a noncompartmental analysis. Geometric mean ratios for the Cmax, area under the concentration‐time curve for 24 hours (AUC0‐24h), and AUC0‐∞, alongside their corresponding 90%CIs, were compared across the study periods to infer clinically significant changes in disposition. The coadministration of AQ and PGZ resulted in decreases of about 38% and 54% in the Cmax and AUC0‐24h of AQ, respectively. For PGZ, the Cmax increased by about 50%, and AUC0‐24 rose by 48%. The 90%CIs of geometric mean ratios for the Cmax, AUC0‐24h, and AUC0‐∞ were all outside the expected bioequivalence interval of 80% to 125% for both drugs, implying significant interactions. These findings suggest that a bidirectional interaction between AQ and PGZ, with likely implications for the therapy and toxicity of both drugs, may occur in the event of their coadministration.

Inter-individual variation in imatinib disposition: any role for prevalent variants of CYP1A2, CYP2C8, CYP2C9, and CYP3A5 in Nigerian CML patients?

Abstract 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.

Moringa oleifera leaf powder alters the pharmacokinetics of amodiaquine in healthy human volunteers

Moringa oleifera (MO) Lam (Moringaceae) is commonly used as food supplement and as medicine in most African countries where malaria is also endemic. Therefore, co‐administration of MO with antimalarials is a possibility. This study investigated the effects of MO leaves powder on the pharmacokinetics of amodiaquine (AQ) in human subjects.