Acetylator status influences bioavailability of isoniazid in patients with advanced HIV disease

Patients with advanced HIV disease may exhibit malabsorption of anti-tuberculosis(TB) drugs. We evaluated the effect of isoniazid (INH) acetylator status on the bioavailability of INH in HIV-infected patients with and without tuberculosis, based on urinary excretion of the drug. Estimation of INH in urine collected up to 8 hours after oral administration of 300 mg INH were undertaken in 23 TB, 40 HIV and 26 HIV-TB patients. Determination of acetylator status of all these patients was also carried by differential estimations of INH and acetyl INH in urine collected between 5 and 6 hours after oral administration of 300 mg INH. Both slow and rapid acetylators in HIV and HIV-TB groups had significantly lower concentration of INH in urine compared to TB patients. The percent decrease in urinary excretion of INH was significantly higher in rapid than in slow acetylators, when compared to the corresponding TB patients. Acetylator status has an impact on the bioavailability of INH. Malbsorption in patients with advanced HIV disease may lead to decreased bioavailability of INH, particularly in rapid acetylators. Urinary estimation of INH provides reliable information on the bioavailability of the drug