The study was carried out to investigate the distribution of polymorphic CY2B6 and CYP2C19 alleles
and genotype frequencies in the three major Nigeria ethnic groups in order to evaluate their
implications on therapeutic outcome. Three hundred unrelated subjects from the three major Nigerian
ethnic groups of Hausa, Ibo and Yoruba who consented to the study were genotyped for CYP2B6*6,
CYP2C19*2 and *3 alleles using polymerase chain reaction/restriction fragment length polymorphism
(PCR/RFLP) and DNA sequencing techniques. The frequencies of the CYP2B6*6 poor metabolizer (PM)
genotype (15631G>T (Q172H) and/or 18053A>G (K262R) were not significantly different (p>0.05)
occurring at 21% in Hausa, 17% in Ibo and 17% in Yoruba while the corresponding allele frequencies
were 42, 36, and 42%, respectively. The frequencies of the CYP2C19 PM genotype (CYP2C19*2/*2) were
significantly different (p>0.05) and found to be 2.1% in Hausa, 8% in Ibo, and 0% in Yoruba, while for the
intermediate metabolizer (IM) genotype (CYP2C19*1/*2), the frequencies were 20.6, 41.6 and 20.8%,
respectively. The defective CYP2C19*3 allele, prevalent in oriental populations, was not detected in this
study. The CYP2B6*6 allele frequency was being evaluated for the first time in Nigerian populations
with no significant variation amongst the three major ethnic groups but occurs at a high frequency. The
PM genotype of frequency, CYP2C19*2/*2 showed significant variations in Nigerian populations,
especially the 8% found in the Ibos.