2-(3,4-dihydroxyphenyl)ethylamine

Distribution
Widely distributed; does not cross the blood-brain barrier to a significant extent.

Metabolism
Metabolized in the liver, kidney, and plasma by MAO and catechol-O-methyltransferase to inactive compounds. Approximately 25% of dose is taken up in the adrenergic nerve terminals where it is hydrolyzed to norepinephrine.

Elimination
t ½ approximately 2 min.

Approximately 80% excreted in the urine within 24 h as metabolites; a very small amount excreted unchanged.

Onset
Within 5 min.

Duration
Less than 10 min.

Furazolidone, methyldopa, rauwolfia alkaloids
Hypertension may result.

Guanethidine
Antihypertensive effects of guanethidine may be negated.

MAOIs
May greatly increase pressor response from dopamine.

Phenytoin
Severe hypotension and bradycardia may result after coadministration with dopamine.

Tricyclic antidepressants
May decrease pressor response from dopamine.

Incompatibility
Chemically incompatible with alkaline solutions (drug is inactivated).