Effect of intravenous infusion of ranitidine on intragastric acidity in fasting subjects: comparison with bolus or Gastrojet (pH-stat-adjusted) infusion

This study was undertaken in nine fasting healthy volunteers to compare the effect of intravenous continuous infusion versus bolus injection of ranitidine on 12-h intragastric pH, and to compare the efficacy of these two modes of administration of pH-stat-adjusted infusion of ranitidine using the Gastrojet. Each volunteer had three study sessions with 12-h pH measurements. In the ranitidine infusion treatment arm (RAN-INF), ranitidine was continually infused intravenously using an IVAC-pump at a dose of 0.125 mg mg.kg over a 12-h period. In the ranitidine bolus treatment arm (RAN-BOL), ranitidine bolus 50 mg was given over 10 min, every 6 h. When ranitidine infusion was given by the pH stat method using the Gastrojet (RAN-JET), sufficient ranitidine was given to maintain a preset value of pH ≥ 5. The study was analysed with a 3 × 3 Latin square cross-over design with multiple measurements of each phase of the cross-over. No difference was found between RAN-INF and RAN-BOL in 12-h or in daytime (10.00–18.00 h) mean pH, median pH, or percentage of pH ≥ 5. Using RAN-JET, 89.5% of the pH values were ≥ 5, compared with 39.7% and 40.0% with RAN-INF or RAN-BOL. RAN-JET also gave higher (P < 0.05) mean and median 12-h or daytime pH values, as compared with RAN-INF or RAN-BOL. The mean doses of ranitidine given in the 12-h infusion periods were 100 mg, 109 mg and 112 mg (RAN-BOL, RAN-INF and RAN-JET, respectively). Thus, this superior inhibition of acid inhibition achieved with Gastrojet does not require higher mean doses of ranitidine. These findings cannot necessarily be applied to persons with duodenal ulcer disease or to patients in an intensive-care unit setting. However, the data do raise the possibility that much greater inhibition of acid inhibition can be achieved by individualizing the dose of ranitidine using the Gastrojet.