A prospective study was conducted to determine the effects of oral ranitidine on gastric pH and volume in outpatients undergoing elective surgery.

Sixty outpatients undergoing elective surgery were randomly assigned to three groups of 20 patients each. Group 1 formed the control group and did not receive the group. Group 2 was given 150 mg ranitidine orally, while group 3 received 300 mg ranitidine, one to five hours prior to induction of anesthesia.

• Mean pH and volume of gastric contents were 1.90 and 27.7 ml, respectively in the control group. Around 90% of the patients in the control group had gastric pH <5. It was noted that pH was < 1.8 in about 65% of the patients. Additionally, 65% of the patients had gastric volumes > 20 ml.
• Ranitidine 150 and 300 mg doses increased mean gastric pH to 6.40 and 5.87, respectively.
• The proportion of patients with gastric pH <5 was reduced to 10% in group 2 and 0% in group 3.
• Mean gastric volume and proportion of patients with volume > 20 ml were also significantly reduced in patients treated with ranitidine.
• Patients with combination of pH <5 and volume > 20 ml were significantly fewer in the ranitidine treatment groups.

To conclude, administration of oral ranitidine prior to surgery, either in 150 mg or 300 mg dose, significantly altered the risk factors in around 95-100% of patients.

Source: Manchikanti L, Colliver JA, Roush JR, Canella MG. Evaluation of ranitidine as an oral antacid in outpatient anesthesia. South Med J. 1985 Jul;78(7):818-22.