Failure of Drugs Acting on H(2)-Receptors to Modify Plasma Prolactin Levels in Pituitary Adenomas: Evidence for a Suprapituitary Locus of Action

Abstract

Cimetidine, which strongly stimulates prolactin release in healthy man, was unable to modify prolactin levels in prolactin-secreting pituitary adenomas. Furthermore, the infusion of 5-methylhistamine, an H(2)-receptor selective agonist, was equally ineffective. The results of these experiments together with the data reported in the literature suggest that H(2)-receptors modulate prolactin secretion at a hypothalamic level.

Effects of H2‐receptor antagonists on the central nervous system

“…cimetidine [Pasquali et al, 19831. Famotidine does not appear to elevate prolactin levels [Hayakawa et al, 1984;Savarino et al, 19861. Cimetidine is thought to act at the hypothalamic level [Scarpignato et al, 1981;Ferrari et al, 19791. In a study in which cimetidine was compared with SKF 92994, an H2-antdgonist 8-10 times more potent but with similar physicochemical properties, only cimetidine produced hyperprolactinernia, leading to speculation that the rise in serum prolactin following 1.v.…”