Effect of histamine-2 receptor blockade by cimetidine on intraocular pressure in humans

The effect of an intravenous infusion of cimetidine (2 mg/kg of body weight/hr) on intraocular pressure and gastric acid secretion was determined in four healthy young adults and compared with the effect of a control infusion of normal saline. Cimetidine, a powerful histamine-2 receptor antagonist, abolished basal acid secretion, indicating that it was pharmacologically active, yet had no effect on intraocular pressure. Therefore, cimetidine may be given safely to patients with normal intraocular pressure. An additional observation was that intraocular pressure in all experiments declined linearly with repeated applanation tonometry for almost two hours before reaching a stable level.