S-mephenytoin hydroxylation phenotype and CYP2C19 genotype among Ethiopians.

The polymorphic metabolism of S-mephenytoin and the distribution of two known deleterious mutant CYP2C19 alleles was determined among 114 healthy unrelated black Ethiopians. Six subjects (5.2%) were poor metabolizers (PMs) of S-mephenytoin. The frequencies of the defective CYP2C192 (CYP2C19m1) and CYP2C193 (CYP2C19m2) alleles were 0.14 and 0.02, respectively. Three of the PMs were homozygous for the CYP2C192 allele and the remaining three PMs were heterozygous for both the CYP2C192 and CYP2C193 mutant alleles. It is concluded that the frequency of PMs for S-mephenytoin is similar in Ethiopians, Zimbabweans and Caucasians and that the CYP2C193 allele, for the first time identified in a black population, together with the CYP2C19*2 allele account for all of the defective CYP2C19 alleles among the Ethiopian PMs.