Dopamine-beta-oxidase activity in man, using hydroxyamphetamine as substrate.

Hydroxyamphetamine was administered orally to five human subjects in daily doses of 26 to 118 mg. Approximately half the dosage administered was recoverable in the urine as unchanged drug (free plus conjugated) and 3.7 to 9.1% was excreted as the beta-hydroxylated metabolite, hydroxynorephedrine (free plus conjugated). Since conversion of hydroxyamphetamine to hydroxynorephedrine occurs in vitro by the action of dopamine-beta-oxidase, a simple method is suggested for measuring the activity of this enzyme and the effect of its inhibitors in man. No impairment of beta-hydroxylation was noted in an adrenalectomized subject. The beta-hydroxylation of hydroxyamphetamine in vivo has not been described previously.