Frequency of Key Pharmacogenes CYP2C9, CYP2C19, CYP2D6, and SLCO1B1 in the Yogyakarta Population: Implications for Precision Prescribing in Indonesia

Genetic variations in CYP2C9, CYP2C19, CYP2D6, and SLCO1B1 significantly influence drug metabolism and transport, impacting therapeutic response and adverse event risk. While pharmacogenomic guidelines advocate for genotype-guided therapy, no population-specific frequency data exist for these pharmacogenes in Yogyakarta, Indonesia-a region where medication use and polypharmacy are common. This study aims to determine the allele and genotype frequencies of CYP2C9, CYP2C19, CYP2D6, and SLCO1B1 in the Yogyakarta, Indonesia population to inform regionally appropriate prescribing practices. Genotyping was performed using probe-specific real-time PCR (RT-PCR) platforms. The panel targeted clinically relevant variants across CYP2C9, CYP2C19, CYP2D6, and SLCO1B1, integrating SNP and copy number variant analysis where applicable. High frequencies of CYP2C19 *2/*3 and CYP2D6*10 alleles were observed, consistent with Southeast Asian profiles. SLCO1B1 reduced-function variants were prevalent, suggesting elevated risk for statin-induced myopathy. CYP2C9*3 allele was also detected, warranting caution in warfarin and NSAID prescribing. The observed genotype distributions highlight the need for region-specific pharmacogenomic strategies in Indonesia. This foundational dataset supports the development of precision prescribing protocols and reinforces the importance of integrating genotyping into clinical practice to improve therapeutic safety and effectiveness.