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. 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. 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) AUC_0–24, C_max and C_min 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). The dried breast milk spot method is simple, robust, accurate and precise, and can be used in settings with limited resources.

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. A total of 110 Nigerians with CML each of whom had been receiving a 400 mg daily dose of imatinib for at least 1 month were genotyped for CYP3A5*3, ABCG2 421C>A and ABCB1 3435 C>T. The TPC of all the patients were determined by a validated HPLC method and possible relationships between genotypes, age, clinical outcome, sex, TPC and ethnicity were analysed. Subjects of TT genotype of ABCB1 C3435T had higher frequencies of complete haematological response (CHR), complete cytogenetic response (CCR) and major molecular response (MMR) but these were not statistically significant (P < 0·05). No genetic polymorphism in ABCG2 421C>A was observed. However, significant associations were observed between TPC and various genotypes in both CYP3A5*3 (P < 0·001) and ABCB1 C3435T (P < 0·001). The GG and TT genotypes in CYP3A5*3 and ABCB1 C3435T, respectively, were linked with higher TPC. This is the first pharmacogenetics study of CML patients in the Nigerian population with ethnic differences in the distribution of ABCB1 C3435T. Genetic polymorphisms in CYP3A5*3 and ABCB1 C3435T are associated with TPC in CML patients in this population.

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. 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. 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. There is evidence of the presence of substandard artemisinin products in the Nigerian market.