Drugs that Interfere with Norepinephrine Synthesis

DRUGS THAT INTERFERE WITH NOREPINEPHRINE SYNTHESIS

Metyrosine (Demser) is an example of this class of drugs. Chemically, metyrosine is -methyl tyrosine. The drug blocks the action of tyrosine hydroxylase, the rate-limiting enzyme in the synthesis of catecholamines. Unlike α-methyldopa, metyrosine is not itself incorpo-rated into the catecholamine synthetic pathway. The ul-timate action of the drug is to decrease the production of catecholamines.

Metyrosine is well absorbed from the gastrointesti-nal tract and is excreted in the urine largely as un-changed drug.

Metyrosine is not employed for the treatment of es-sential hypertension but rather is used for the manage-ment of pheochromocytoma. It is useful for preopera-tive treatment and for long-term therapy when surgery is not feasible.

Sedation is the most common adverse effect of metyrosine. Other CNS disturbances, such as anxiety, confusion, and disorientation, have also been reported. Symptoms of sympathetic nervous system depression in general, such as nasal congestion and dryness of mouth, can also occur.