Gastric ulcerogenic and healing impairment effects of risedronate, a nitrogen-containing bisphosphonate in rats. Comparison with alendronate and minodronate.

We examined the mucosal irritating and healing impairment effects of risedronate, a nitrogen-containing bisphosphonate (BPP), on rat stomachs, in comparison with those of alendronate and minodronate. Male SD rats were used in the following two studies; 1) the ulcerogenic effects of risedronate, alendronate and minodronate in the antral mucosa, and 2) the healing impairment effect of these drugs on gastric ulcers induced by thermocauterization. A single administration of BPPs to fasted rats produced ulcers in the antrum with severe edema and inflammation 3 days after refeeding, although the doses required for this action differed among these BPPs: alendronate >100 mg/kg, risedronate >300 mg/kg, minodronate >10 mg/kg. The generation of antral ulcers induced by these BPPs was accompanied by an increase in myeloperoxidase (MPO) activity and lipid peroxidation as well as a decrease in superoxide dismutase (SOD) activity and glutathione (GSH) content in the mucosa; the extent order of these changes was minodronate >alendronate >risedronate. On the other hand, the healing of gastric ulcers was significantly delayed by daily administration of alendronate (>30 mg/kg) and minodronate (>10 mg/kg), but not by risedronate, even at 60 mg/kg. Mucosal vascular endothelium-derived growth factor (VEGF) and basic fibroblast growth factor (bFGF) protein expressions were up-regulated after ulceration, in parallel with angiogenesis. Alendronate and minodronate decreased these expressions and angiogenesis, while risedronate had no effect. In conclusion, the gastric adverse effect of risedronate is less potent than alendronate and minodronate. It is assumed that risedronate may be used more safely than other BPPs as an antiresorptive drug in patients.