Drug Interaction Report

MONITOR: Concurrent use of phenothiazines and phenytoin may increase the effect of phenytoin and decrease the effect of the phenothiazine. The mechanism is unknown and clinical data have been inconsistent.

MANAGEMENT: Close monitoring for clinical and laboratory evidence of phenytoin toxicity is indicated. Patients should be advised to notify their physician if they experience symptoms of possible hydantoin toxicity, including drowsiness, visual disturbances, change in mental status, seizures, nausea, or ataxia.

GENERALLY AVOID: Concurrent use of ethanol and phenothiazines may result in additive CNS depression and psychomotor impairment. Also, ethanol may precipitate dystonic reactions in patients who are taking phenothiazines. The two drugs probably act on different sites in the brain, although the exact mechanism of the interaction is not known.

MANAGEMENT: Patients should be advised to avoid alcohol during phenothiazine therapy.