The effects of bromocriptine in methyldopa treated hypertension.

1. The effects of treatment with the dopaminergic agonist bromocriptine were studied in nine patients with essential hypertension receiving methyldopa as sole therapy. 2. In Phase 1 of the study, the addition of bromocriptine on a single-blind basis caused a significant fall in lying and standing blood pressures. Plasma prolactin fell significantly but there was no significant change in the other biochemical parameters measured. All patients volunteered that they felt a sense of well-being after starting bromocriptine treatment. 3. In Phase 2 of the study the substitution of placebo for bromocriptine in a randomized double-blind trial significantly increased lying and standing blood pressures and plasma prolactin. No consistent or significant changes were observed in methyldopa-induced side-effects following the substitution of placebo for bromocriptine. 4. In Phase 3 of the study, a gradual increase in blood pressure was observed in all patients over a few months after stopping bromocriptine therapy. 5. The significance of these findings in relation to the role played by plasma prolactin and central dopaminergic activity in blood pressure regulation is discussed.