Plasma prolactin, sex steroids and gastrin in human volunteers treated for 2 weeks with therapeutic doses of cimetidine or the new histamine H₂-receptor antagonist ramixotidine (CM 57755A)

Three groups of eight healthy male volunteers received placebo for 2 days, then daily morning doses either of cimetidine 800 mg, ramixotidine 750 mg (CM 57755A), or placebo, for 14 days, and then were all returned to placebo for one more day. Plasma levels of prolactin, testosterone and 17β-estradiol were measured on Days 2, 3, 16 and 17 in blood samples taken 30 and 15 min before and 0, 60, 120, 180, 240 and 300 min after treatment. Gastrin was assayed in blood collected on the same days 180 min after treatment. Mean pre- and post-treatment areas under the time-concentration curves of the first three hormones were not significantly different in the three groups on any test day, or within the same group throughout the four test days. Mean plasma gastrin levels ranged between 27 and 42 pg/ml, respectively, in the placebo and cimetidine treated groups on test day 3, and intermediate values were found in the group receiving CM 57755A. There was no statistically significant difference in gastrin level between the groups on any test day or within the same group throughout the four test days. No subjective side-effects attributable to the treatments were reported, and there were no abnormalities in blood pressure, heart rate or standard laboratory tests.