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The administration of a dopamine antagonist, chlorpromazine, and two opiates, morphine and methadone, resulted in a significant rise in serum PRL within 90-150 min. Prior administration of dopamine receptor agonists (apomorphine, levodopa, aand bromocriptine) blocked this effect. In contrast, cyproheptadine, a serotonin antagonist, did not. We suggest that the opiates induce hyperprolactinemia in man via dopamine receptor blockade.

Labetalol (5-1 hydroxy-2 (1-methyl-3 phenyl amino salicylamide hydrochloride)) is a new antihypertensive agent having partial alpha- and beta-adrenoreceptor-blocking properties. Nine patients with mild, moderate or severe hypertension have been given this drug over periods ranging from 6-29 weeks. Labetalol was given as replacement for a beta-blocking drug providing less than satisfactory control. Adequate control of blood pressure was achieved in all nine patients. The only side-effect of note was postural hypotension which necessitated withdrawal of the drug in one patient.