Alendronate induces gastric injury and delays ulcer healing in rodents

Gastric ulceration associated with the use of NSAIDs is most frequently observed in elderly women, the same sector of society most likely to be receiving therapy for osteoporosis. As some anti-osteoporosis medications have been suggested to irritate the upper gastrointestinal mucosa, we evaluated the ability of one such drug, alendronate, to damage the gastric mucosa and to influence the severity and healing of gastric ulcers in rodents. The effects of alendronate on indomethacin-induced antral ulceration was evaluated in the rabbit, while effects on ulcer healing and on the formation of gastric erosions was evaluated in the rat. Effects of alendronate on gastric acid secretion, blood flow and prostaglandin synthesis were also evaluated. Alendronate caused erosions in the rabbit stomach, but not antral ulceration. However, at the highest doses tested (80 mg) alendronate increased the incidence and size of indomethacin-induced antral ulcers. Alendronate also enhanced indomethacin-induced gastric damage in the rat, and delayed gastric ulcer healing. These effects of alendronate were not attributable to changes in gastric acid secretion, blood flow, prostaglandin synthesis or the pharmacokinetics of indomethacin. The damaging effects of alendronate on the stomach were due to topical irritant effects and could be observed at concentrations as low as 4 mg/ml within 30 min of oral administration or topical superfusion. These results support preliminary clinical evidence that alendronate can damage the gastric mucosa. While gastric injury may be a rare occurrence in patients taking this drug, concomitant use of alendronate and NSAIDs may increase the incidence or severity of ulceration.