Acetylation phenotype, platelet monoamine oxidase inhibition, and the effectiveness of phenelzine in depression.

The authors treated 16 depressed patients with up to 90 mg/day of phenelzine. After acetylation phenotype was determined and platelet monoamine oxidase (MAO) activity measured, no significant relationship was observed between clinical improvement and acetylation phenotype or between MAO inhibition and acetylation. Discrepant findings regarding acetylation phenotype and the effects of phenelzine are discussed. The authors do not recommend a sulfamethazine phenotype test as a predictor of outcome for phenelzine.