Liquid chromatographic-mass spectrometry analysis and pharmacokinetic studies of a novel rabeprazole formulation, sterile powder for injection, in dogs and rats.

Rabeprazole is among the most potent proton pump inhibitors (PPI) identified to date and it has been demonstrated that it is effective in such diseases as gastroesophageal reflux disease (GERD), duodenal ulcer and gastric ulcer. There is currently interest in developing a new formulation: rabeprazole sterile powder for injection (RSPI). This investigation was conducted to evaluate the preclinical pharmacokinetics of RSPI in rats and at the same time a comparative study was carried out in dogs between RSPI and Pariet tablets using liquid chromatographic-mass spectrometry analysis. The liquid chromatographic-mass spectrometry method was first conducted and validated as being specific, and having accuracy, precision, sensitivity and a satisfactory recovery. After intravenous administration of RSPI (i.v.: 2, 6 and 18 mg/kg) to rats, no significant dose-dependency was found in the CL (4.20-5.72 l/h/kg), V(area) (d) (0.94-1.32 l/kg), dose-normalized AUC (197.20-245.82 microg/l*h based on 1 mg/kg) and t(1/2) (p>0.05). In the dog, a randomized, open-label, crossover experiment was carried out to show that the mean area under the plasma concentration-time curve (AUC(0-infinity)) after i.v. administration of RSPI was at least four times larger than that following oral administration of Pariet tablet at an equivalent dose but the elimination half-life of these two formulation was similar (p>0.05). The results showed that the pharmacokinetics of RSPI was linear (r(2) = 0.98) in the dose range 2-18 mg/kg and the RSPI had a much higher AUC(0-infinity) and similar t(1/2) values compared with the enteric-coated tablet.