Unchanged acetylation of isoniazid by alcohol intake.

SETTING

In 10 healthy subjects, the influence of acute alcohol intake on the pharmacokinetics of isoniazid (INH) was studied.

OBJECTIVE

To test the hypothesis that alcohol increases the conversion of INH by acetylation into its metabolite acetylisoniazid.

DESIGN

In a crossover design, an oral dose of 300 mg INH was administered on 2 separate days, 14 days apart, with or without alcohol to a serum alcohol of about 21 mmol/l (1 g/l) maintained for 12 h.

RESULTS

Neither the metabolism of INH nor that of acetylisoniazid was changed by acute alcohol intake.

CONCLUSION

Acute alcohol intake has no impact on the conversion of INH to its metabolite acetylisoniazid, which is catalysed by the enzyme N-acetyltranferase. Accordingly, a metabolic effect of acute alcohol intake on INH metabolism probably contributes little to the therapeutic failure of anti-tuberculosis treatment among alcoholics.