Ｒａｎｉｔｉｄｉｎｅ低用量投与時の胃内ｐＨの変動 テトラガストリン刺激に対して

Abstract

Effect of low-dose ranitidine on gastric pH after stimulation of gastric fluid secretion was evaluated using 4μg/kg of intramuscularly administered tetragastrin (TG) in 12 healthy male volunteers. The study was a randomized, placebo-controlled, four-way, cross-over trial. A wash-out period of 1-week was maintained between each treatment. Treatment administration was as follows: (1) 14.06 mg (hereafter 14mg) ranitidine, TG at t=1hr.(2) 28.13 mg (hereafter 28mg) ranitidine, TG at t=1hr.(3) 56.25mg (hereafter 56mg) ranitidine, TG at t=1hr.(4) Placebo, TG at t=1hr. Gastric pH was continuously monitored for 6 hours through a micro-pH-electrode in every subject. Gastric fluid acidity was measured at t=0, 1, 2, 3, 4 and 5 hr after ranitidine administration. Average gastric pH values for 6 hours were increased by ranitidine treatment from 2.08±0.48 (placebo) to 3.60±1.10 (14 mg, p<0.05 vs placebo), to 3.83±1.41 (28mg, p<0.05 vs placebo), and to 4.76±1.50 (56 mg, p<0.05 vs placebo, 14mg, 28mg).A dose-related increase in pH holding time was also observed. Gastric acidity was increased with TG in the placebo group from 53.1±27.6mEq/L (t=1hr) to maximum 120.8±31.8mEq/L (t=2hr) and returned to baseline value at t=5hr. Ranitidine treatment significantly suppressed the increase in gastric acidity in a dose-related manner (t=2hr: 14mg, 103.9±18.0 mEq/L: 28mg, 98.9±25.6mEq/L: 56mg, 77.1±36.5mEq/L). The results indicated that low-dose ranitidine inhibited the secretion of gastric fluid induced by TG administration and increased gastric pH in a dose-related manner.