Drug Interaction Report

MONITOR: Coadministration of metyrosine in combination with haloperidol, phenothiazines, or other dopamine antagonists may increase the risk of extrapyramidal disorders. Extrapyramidal effects have been reported during metyrosine therapy. The mechanism is inhibition of catecholamine synthesis by metyrosine. In addition, sedative effects of both drugs may be increased.

MANAGEMENT: When concurrent use is required, patients should be monitored for extrapyramidal symptoms and instructed to notify their physician if they experience symptoms such as bradykinesia, hypertonia, rigidity, restlessness, and dysphagia. Patients should also avoid driving or operating hazardous machinery until they know how the medications affect them.

MONITOR: Metyrosine, when coadministered with other CNS depressants including alcoholic beverages, may lead to excessive somnolence and other forms of nervous system depression.

MANAGEMENT: The patient should be informed to use caution if these agents are coadministered, especially if performing hazardous tasks such as driving or operating machinery.

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.