Time Required for Oral Ranitidine to Decrease Gastric Fluid Acidity

Abstract

This study documented gastric fluid acidity in ambulatory surgical patients 30-120 min after they had taken a 300-mg tablet of ranitidine, as changes specific to this relatively brief dose-to-sampling interval previously had not been delineated. At 20-120 min before outpatient surgery, ranitidine was given with 15 mL of water to 112 ASA physical status I-III adults without increased risk factors for aspiration of acidic gastric contents. After induction of general endotracheal anesthesia, the gastric fluid was aspirated. Volume and pH were compared with a reference group (pH = 1.6 +/- 1; n = 161) that did not receive an H2-antagonist or water. Of 40 patients sampled at 30-60 min after dosing, 26 had pH greater than or equal to 2.5; mean pH was 3.9 +/- 2 (P less than 0.05 vs reference by Wilcoxon signed rank and chi 2 tests). Beyond 90 min, 28 of 28 patients had a pH greater than or equal to 2.5, with a mean of 6.3 +/- 1. No significant differences were noted with respect to mean gastric volume. We conclude that in patients without additional risk factors, oral ranitidine consistently prevents acid production when it is administered more than 90 min before induction of anesthesia.

The efficacy and optimum time of administration of ranitidine in the prevention of the acid aspiration syndrome

“…Jacobs et al [7] found that, 90min after oral administration of ranitidine 300 mg, all patients had a pH > 2.5 but, during the period between 30 and 90 rnin after administration of the same oral dose, 25.6% of the patients had a pH < 2.5. However, no differences were found with respect to volume.…”

“…ambulatory surgery), it would be practical to shorten this period of time. Jacobs et al [7] have shown that a single dose of ranitidine 300 mg orally provided pulmonary protection 90 min after administration.…”

Regular use of H2 blockers reduces the efficacy of roxatidine to control gastric pH and volume

“…Oral roxatidine 75 mg was given twice, once at 21:00 on the night before surgery and again 90 min before induction of anesthesia in the present study. Jacobs et al 12 reported that oral ranitidine 300 mg (equivalent to roxatidine 150 mg) consistently prevents acid production when given more than 90 min before induction. However, the data reported by Atanassoff et al 13 suggest that oral ranitidine 150 and 300 mg produce peak gastric elevation of pH (~ 7) at eight and 12 hr following administration.…”

A marked increase in gastric fluid volume during cardiopulmonary bypass

“…(8,9) These reports (8,9) also suggest that tolerance to PPI treatment would not develop as PPIs inhibit the H + /K + -adenosine triphosphatase pump, which is the final step in gastric acid secretion from the parietal cell. (10) …”