The effect of thyrotoxicosis on isoniazid acetylation

Isoniazid acetylation was assessed in 10 thyrotoxic patients before and after standard antithyroid therapy. The group contained five fast and five slow acetylators and all remained within the same phenotypic classification when rendered euthyroid. There was no significant change in the elimination half-life of isoniazid between thyrotoxicosis and euthyroidism for the group as a whole or for fast and slow acetylators considered separately. Thyrotoxicosis does not appear to be an important determinant of isoniazid acetylation in man.