Pharmacodynamic effects of 3-day intravenous treatment with pantoprazole or ranitidine after 10 days of oral ranitidine

Tachyphylaxis (drug tolerance) is an undesirable condition in drug therapy with histamine-2-receptor antagonists (H2RAs). The concept of overcoming tachyphylaxsis via intravenous (i.v.) administration of proton-pump inhibitors (PPIs) or H2RAs is of significant interest to physicians. In the present study, 32 healthy Helicobacter pylori negative male volunteers were evaluated for the ability of i.v. pantoprazole or i.v. ranitidine to overcome oral ranitidine tachyphylaxis. After 10 days of oral treatment with enteric-coated 300-mg ranitidine tablets once daily in the evening, two groups of 16 volunteers each were randomized to receive either i.v. pantoprazole or i.v. ranitidine for up to 72 h. The primary variable was defined as the increase in 24-h gastric pH median after 1 day of i.v. treatment; the secondary variable was median percentage of time that 24-h gastric pH was <4, as calculated by Hodges-Lehman shift estimators. After 10 days of oral ranitidine treatment, tachyphylaxis was present in all volunteers. Within 1 day of continuous i.v. pantoprazole or i.v. ranitidine administration, 24-h median gastric pH increased from pH 1.45 to pH 3.50 (241%) and from pH 1.50 to pH 2.35 (157%), respectively. I.v. pantoprazole was found to be significantly more effective (p<0.05) than i.v. ranitidine in increasing the 24-h gastric pH after oral ranitidine tachyphylaxis.

Bioavailability of a crushed pantoprazole tablet after buffering with sodium hydrogencarbonate or magaldrate relative to the intact enteric coated pantoprazole tablet

The aim of this study was to determine the bioavailability of orally administered, crushed pantoprazole tablets after buffering with either 1.4% sodium hydrogencarbonate or 1600 mg magaldrate relative to the intact enteric coated pantoprazole tablet. A single dose, three-period crossover study was performed with 18 healthy male volunteers. The crushed pantoprazole suspension, together with either sodium hydrogencarbonate or magaldrate, was administered via a nasogastral tube. Tmax of crushed pantoprazole was earlier as compared to the intact tablet (0.5 h vs. 3 h) and Cmax was approximately 10% higher due to faster absorption. The bioavailability of the crushed pantoprazole tablet relative to the intact pantoprazole tablet was 93% when using sodium hydrogencarbonate as the buffering agent, and 88% when using magaldrate. Based on the internationally approved confidence intervals for AUC (0.80-1.20) and Cmax (0.70-1.43), the crushed tablet buffered with sodium hydrogencarbonate was shown to be bioequivalent with the intact tablet (point estimates for AUC or Cmax: 0.93 or 1.10). For the crushed tablet buffered with magaldrate (point estimates for AUC or Cmax: 0.88 or 1.12) bioequivalence with the intact tablet could not be formally demonstrated, although the lower confidence limit for AUC of 0.78 was only slightly below the lower limit of the equivalence range of 0.80.