The effects of oral rabeprazole on endocrine and gastric secretory function ill healthy volunteers

Aim: To evaluate the short-term effects of rabeprazole 20 mg on endocrine p arameters, in particular serum testosterone and cortisol, and on 24 h intra gastric pH, H+ activity and nocturnal gastric acid secretion. Methods: In this double-blind, two-period crossover study, 12 healthy young male volunteers were randomly given oral rabeprazole 20 mg o.m. or placebo for 14 days, There was a washout period of tit least 1 week between the tw o studies, The effects of rabeprazole and placebo on cortisol and testoster one (primary criteria), and on tri-iodothyronine, thyroxine, 17 beta-oestra diol, thyroid-stimulating hormone, thyroxine-binding protein, parathyroid h ormone, insulin, glucagon, rennin, aldosterone, follicle-stimulating hormon e, luteotrophic hormone, prolactin, somatotrophic hormone, dehydroepiandros terone. cortisol-binding globulin and urinary 6-beta hydroxycortisol were c ompared. Intragastric 24 h pH, 24 h H+ activity and nocturnal gastric acid secretion were determined by pH probe and gastric aspiration. Results: Rabeprazole produced no clinically relevant effects on endocrine f unction as assessed by measure-ment of serum testosterone, circadian serum cortisol levels, ACTH-stimulated serum cortisol levels and 17 other endocri ne function tests. Rabeprazole significantly increased the 24 h median pH v alues compared to placebo (on Days 7 and 14 median values ranged from 3.92 to 6.88 with rabeprazole and from 1.48 and 4.22 with placebo, P < 0.001) an d significantly decreased the integrated 24 h H+ activity (AUC(08-08)) from 343 mmol/L/h with placebo to 44 mmol/L/h with rabeprazole (P < 0.001). Fol lowing cessation of dosing, intragastric pH levels decreased and H+ activit y increased, but acid secretion did not recover completely during the next 72 h. The mean value for nocturnal gastric acid secretion on Days 7 and 8 w as 36 mmol/6 h with placebo and 5.6 mmol/6 h with rabeprazole (P < 0.001), Rabeprazole was well tolerated. Conclusion: Rabeprazole did not influence endocrine function in healthy you ng male volunteers during short-term dosing, Rabeprazole substantially incr eased intragastric pH over a 24 h period and significantly decreased intrag astric acidity and nocturnal gastric acid secretion.