Summary: | Polymorphisms in the genes encoding CYP2C9 enzyme and VKORC1 reductase significantly influence the dose variability of coumarinic oral anticoagulants (COAs). Substantial inter- and intraethnic variability exists in the frequencies of CYP2C9
∗2 and ∗3 and VKORC1 –1639A alleles. However, the prevalence of CYP2C9 and VKORC1 genetic variants is less characterized in Arab populations. A total of 131 healthy adult subjects from the Al-Ahsa region of Saudi Arabia were genotyped for the CYP2C9
∗2 and ∗3 and VKORC1 –1639G>A polymorphisms by PCR-RFLP method. The frequencies of the CYP2C9
∗2 and ∗3 and VKORC1 –1639A alleles were 13.3%, 2.3%, and 42.4%, respectively, with no subjects carrying 2 defective alleles. The frequencies of the CYP2C9
∗3 and VKORC1 –1639A alleles were significantly lower than those reported in different Arabian populations. None of the subjects with the VKORC1 –1639AA genotype were carriers of CYP2C9
∗1/∗3 genotypes that lead to sensitivity to COAs therapy. The low frequency of the CYP2C9
∗3 allele combined with the absence of subjects carrying 2 defective CYP2C9 alleles suggests that, in this specific population, pharmacogenetic COAs dosing may mostly rely upon VKORC1 genotyping.
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