Isoniazid acetylation phenotyping in Saudi Arabs.

Aims: The present study is designed to investigate the acetylator status in Saudi Arabs.

Methods: Isoniazid (INH) acetylation phenotyping was studied in 136 Saudi Arabs in Riyadh, Saudi Arabia, using a single plasma sample taken 3 h post-INH oral dose of 200 mg. Metabolic ratio (MR) of plasma acetyl-INH (Ac-INH) to INH was used to determine the acetylation phenotype.

Results: The MR had a bimodal distribution with an antimode of 1.0. The frequency distribution of slow acetylators (MR < 1.0) was 94.9% (n = 129). Using Hardy-Weinberg Law, the gene frequency (q) of the recessive allele determining slow acetylator phenotype was found to be 0.97.

Conclusion: INH phenotyping suggests a high frequency of slow acetylators among Saudi Arabs. There was no association between the MR of plasma Ac-INH/INH and age or gender.