Blood pressure and prolactin: effects of guanfacine. Three-year follow-up study

Serum prolactin was measured in 76 patients with essential hypertension: 47.4% had elevated serum prolactin, and those with organ damage had presented higher prolactin than those with Phase I (WHO) hypertension. The effect of prolonged treatment (3 years) with guanfacine, an alpha-adrenoceptor stimulant drug, on blood pressure levels, heart rate, and prolactin was evaluated in 15 patients with moderate essential hypertension (WHO: Phase II) and hyperprolactinemia. Treatment produced a marked reduction in blood pressure levels and heart rate. Guanfacine decreased serum prolactin significantly (p less than 0.001), and the inhibition persisted during the 3-year follow-up. The daily dosage of guanfacine did not have to be changed during the 3 years of treatment. Side effects of guanfacine were only observed during the first 3-4 months of therapy. The hypotensive effect of guanfacine was increased by the administration of a diuretic, a vasodilator, or a beta-adrenergic blocking drug. The results indicate that guanfacine administered alone or in combination is an effective drug for treatment of patients with essential hypertension. The inhibitory effect of guanfacine on prolactin suggests that hypothalamic or extrahypothalamic adrenergic pathways may participate in the regulation of prolactin secretion.