The inter-patient differences in drug response is documented to be attributable to heritable genetic variations in the nucleotide sequence of drug-metabolizing enzymes. The identification of variant allele frequencies in specific ethnic groups is important to individualize drug dosing and improve therapeutics. This study aimed to detect single-nucleotide polymorphism (SNP) in CYP3A4 and the homozygous deletion (0/0) of GSTM1 and GSTT1 in a Filipino population. Onehundred and forty-two Filipino subjects were genotyped for the CYP3A4*18 SNP using PCR-RFLP and the GSTM1 0/0 and GSTT1 0/0 by basic PCR followed by agarose gel electrophoresis. In the study population, the frequency of the CYP3A4*18 variant allele was found to be 2.11%. The percentage of GSTM1 0/0 observed was 64.08 while that of GSTT1 0/0 was 48.59. These frequencies complement studies in other Asian populations highlighting the importance of the screening for future prospects of individualized medicines.
Keywords: CYP3A4*18, GSTM1, GSTT1, gene polymorphisms, drug metabolism.