A prospective comparison of the effects of placebo, ranitidine and highly selective vagotomy on 24 h ambulatory intragastric pH in patients with duodenal ulcer.

Twenty-four hour ambulatory intragastric pH (24 h IGpH) recording, a highly reproducible technique, was used to compare the effects of ranitidine and highly selective vagotomy (HSV) in 20 patients who had been referred for surgical treatment of duodenal ulcer. The 24 h IGpH was recorded when they were taking either placebo or ranitidine 300 mg at 10 pm, and again 4 to 13 weeks after elective HSV. Median 24 h IGpH and 24 h hydrogen ion activity (24 h [H+]) were calculated for each patient. Median (quartile) 24 h IGpH was 1.4 (1.3-1.6) with placebo, 2.2 (1.8-2.7) after ranitidine and 2.6 (1.8-3.7) after HSV. IGpH was significantly higher after both ranitidine (P less than 0.0001) and HSV (P less than 0.0001) than after placebo, but IGpH after ranitidine did not differ from IGpH after HSV (0.5 greater than P greater than 0.4). HSV reduced 24 h [H+] by a median 68 per cent (quartiles, 47-82 per cent) whereas ranitidine reduced it by only 50 per cent (34-69 per cent, 0.1 greater than P greater than 0.05). The 24 h pH recording was then analysed as two distinct periods; 'daytime' (8 am to midnight) and 'night-time' (midnight to 8 am). HSV reduced daytime [H+] by a median 77 per cent (59-93 per cent) whereas ranitidine reduced it by only 30 per cent (13-45 per cent, P less than 0.0001). HSV reduced night-time [H+] by a median 57 per cent (40-83 per cent) but ranitidine reduced it by a median 92 per cent (78-98 per cent, P less than 0.01). Thus, HSV inhibits gastric acidity more during the day than at night, whereas ranitidine given at 10 pm effectively suppresses night-time acidity but is much less effective in suppressing daytime acidity. However both HSV and ranitidine will heal more than 90 per cent of duodenal ulcers. Hence, contrary to Dragstedt's teaching, suppression of nocturnal acidity is not of crucial importance for the healing of duodenal ulcers.