['We have previously shown that 70% of patients experience nocturnal gastric acid breakthrough (defined as pH<4 for more than 60 min between 22.00 and 06.00 hours) on twice a day (b.d.) proton pump inhibitor. Adding 150 or 300 mg of ranitidine at bedtime is more effective than additional omeprazole at bedtime in control of night-time acid breakthrough.', 'To assess whether omeprazole 20 mg AM plus ranitidine 150 mg HS would be as effective as omeprazole 20 mg before breakfast and dinner (b.d. AC) in intragastric pH control, particularly during the overnight period.', 'Twenty healthy volunteers (11 males, 9 females, mean age 32.7 years) were treated with omeprazole (OME) 20 mg b.d. AC and placebo HS or omeprazole 20 mg AM and placebo before dinner plus ranitidine (RAN) 150 mg HS for 7 days, in a randomized, double-blind, crossover design, with a 1 week washout between study periods. On day 8 subjects were monitored for 24 h with a single channel pH probe placed in the stomach 10 cm below the proximal border of the LES. Percentage time pH<4 for total, upright and recumbent positions were compared between the two regimens using Wilcoxon matched pairs testing.', 'Expressed in median values of percentage time pH<4: upright time intragastric pH<4 on OME 20 mg b.d. AC was 18.9 compared to 29.7 on OME AM + RAN HS (P = 0.003). Recumbent time pH<4 on OME 20 mg b.d. AC was 23.45 compared to 44.75 on OME AM + RAN HS (P = 0.02).'] Does bedtime ranitidine eliminate the need for a second daily dose of omeprazole to suppress nocturnal gastric pH?