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

In order to evaluate the efficacy of a single oral dose of ranitidine 150 mg and the optimum time for its administration, we studied pH and volume measurements in 138 surgical patients, who formed six groups according to the time elapsed from ranitidine administration to gastric fluid aspiration as follows: group A: no ranitidine, group B: 60-90 min, group C: 91-120 min, group D: 121-150 min, group E: 151-180 min and group F: > 180 min. The patients from groups B, C, D, E and F had a significant increase in gastric pH and a significant decrease in gastric fluid volume when compared to the patients from group A. 33.3% (95% CI 16.63%-53.22%) of patients in group A were deemed 'at risk' of acid aspiration compared to 0.9% (95% CI 0.02-4.90%) in other groups. No significant differences were found between the patients receiving ranitidine after 60 min with respect to risk of acid aspiration. It is concluded that a single oral dose of ranitidine 150 mg is effective against the acid aspiration syndrome 60 min after administration.