A study was conducted with the objective of assessing three oral dosing regimens of ranitidine, given preoperatively, in ambulatory patients having significant risk of aspiration pneumonitis (gastric pH < 2.5 or volume > 25 ml at intubation or extubation).

The double-blind, placebo-controlled, randomized study included 271 ambulatory patients scheduled for surgery under general anesthesia. In all, 241 of these completed the trial. Patients were randomized to one of the following four regimens given orally prior to surgery:

• Placebo at bedtime the night prior to surgery and in the morning on the day of surgery
• Ranitidine 150 mg at bedtime and in morning
• Ranitidine 150 mg at bedtime and placebo in morning
• Ranitidine 300 mg at bedtime and placebo in morning.

Study findings -

• Patients administered ranitidine 150 mg twice a day, ranitidine 150 mg at bedtime, or ranitidine 300 mg at bedtime were found to have a significantly (p < 0.05) lower frequency of a gastric pH <5 at intubation or extubation compared to patients administered placebo twice a day (3%, 45%, and 31%, respectively, vs. 86%).
• Significantly lesser patients receiving ranitidine 150 mg at bedtime had gastric volume at intubation or extubation >25 ml, compared to placebo (37% vs 13%, p < 0.05).
• The number of patients with risk factors for aspiration pneumonitis was found to be significantly lower with ranitidine 150 mg twice/day, ranitidine 150 mg at bedtime, and ranitidine 300 mg at bedtime than placebo (20%, 48%, 35%, respectively, vs. 86%; p < 0.001). It was significantly lower with ranitidine 150 mg twice a day compared to ranitidine 150 mg at bedtime (p < 0.05).

It was concluded that ranitidine 150 mg twice/day given preoperatively led to the greatest reduction in the percentage of patients who had significant risk factors for aspiration pneumonitis following surgery.

Source: O’Connor TA, Basak J, Parker S. The effect of three different ranitidine dosage regimens on reducing gastric acidity and volume in ambulatory surgical patients. Pharmacotherapy. Mar-Apr 1995;15(2):170-5.