Effect of two doses of pirenzepine on histamine-stimulated gastric acid secretion in man.

The effect of two dose-schedules of Pirenzepine (25 mg b.d. or 50 mg t.d.s. during 2 1/2 days) on histamine-stimulated gastric acid secretion was tested in eleven healthy volunteers. Gastric secretory responses were calculated as acid output values and as VG-values (VG = gastric secretory volume corrected for duodeno-gastric reflux and pyloric loss). Stimulated acid output per two hours was reduced with Pirenzepine 25 mg b.d. by 12.5% (n.s.), with Pirenzepine 50 mg t.d.s. by 21% (p less than 0.01). Stimulated VG per two hours was reduced with Pirenzepine 25 mg b.d. by 15.8% (p less than 0.01) and with Pirenzepine 50 mg t.d.s. by 24% (p less than 0.01). Pirenzepine reduces histamine-stimulated gastric acid output to a similar degree as other anticholinergic drugs. Reduction seems to be due to true inhibition of acid secretion and not to altered gastric motility.

Intragastric nitrites, nitrosamines, and bacterial overgrowth during cimetidine treatment.

A six week course of cimetidine (1 g/day) healed peptic ulcers in 20 of 23 patients (14 with duodenal ulcer, nine with gastric ulcer). Reduction of basal acid output by 73% and peak acid output by 36% led to a rise in concentrations of intragastric aerobic bacteria and nitrate-reducing bacteria. While the mean intragastric concentration of nitrate was unchanged by treatment, there were statistically significant rises in nitrite and N-nitrosamine concentrations. The conversion from nitrates to nitrites was closely related to the occurrence of nitrate-reducing bacteria. In three patients the intragastric milieu had returned to normal two months after cimetidine treatment had been discontinued. Mean nitrite and N-nitrosamine concentrations did not return to pre-treatment levels in the group of eight patients who remained on maintenance cimetidine (0.4 g at night-time) for three months after the full dose treatment. This study shows that cimetidine treatment can create an intragastric milieu resembling that of atrophic gastritis. Large scale and long-term studies are necessary to establish whether these findings have any clinical significance.