Background: Cytochrome P450 (CYP) contributes to a huge collection of medicinal products'
Phase I metabolization. We aimed to summarize and investigate the current evidence regarding
the frequency of CYP2D6, CYP2C9, CYP2C19, and MDR1 in Saudi Arabia.
Methods: A computerized search in four databases was done using the relevant keywords. The screening
process was done in two steps; title and abstract screening and full-text screening. Data of demographic
and characteristics of included studies and patients were extracted and tabulated.
Results: Ten studies were eligible for our criteria and were included in this systematic review. The age
of participants ranged between 17-65 years. Only two subjects showed PM phenotype of CYP2C19 in
the Saudi population. The most frequent alleles were CYP2C19*1 (62.9%), CYP2C19*2 (11.2%-32%),
and CYP2C19*17 (25.7%). The CYP2C19m1 was observed in 97 cases of extensive metabolizing (EM)
phenotype CYP2C19. Concerning the CYP2C9, the most frequent alleles were CYP2C9*1 and
CYP2C9*2, and the most frequent genotype was CYP2C9*1*1. The CYP2D6*41 allele and C1236T
MDR1 were the most frequent allele in this population.
Conclusion: The current evidence suggests that Saudi resembled European in the frequency of
CYP2C19, Caucasians in both the incidence of CYP2C9 and CYP2C19m1, and the absence of
CYP2C19m2. The CYP2D6*41 allele frequency in Saudi is relatively high. We recommend further research
to evaluate the basic and clinical relevance of gene polymorphism in such ethnicity.