Toxic Effects of High-dose Meloxicam and Carprofen on Female CD1 Mice

The nonsteroidal anti-inflammatory drugs meloxicam and carprofen are commonly used as analgesics in mice. The current recommended doses of meloxicam at 0.2-1.0 mg/kg once daily and carprofen at 5-10 mg/kg twice daily may not be adequate to provide analgesia in mice. Several studies have suggested that doses up to 20 mg/kg of meloxicam and carprofen are needed to provide analgesic efficacy. This study investigated the clinical safety of these higher doses of meloxicam and carprofen by evaluating their potential for renal and gastrointestinal toxicity. Female CD-1 mice were given 20 mg/kg of either meloxicam, carprofen, or an equivalent volume of saline subcutaneously once daily for 3 or 7 d. On day 4, mice treated for 3 d were euthanized, and on days 8 and 15, mice treated for 7 d were euthanized. Blood was collected by cardiocentesis for serum chemistry analysis. Feces was collected from the colon for fecal occult blood testing, and tissues were collected for histopathology. No clinically significant changes in serum chemistry profiles were found in the drug-treated mice at any time point as compared with the saline controls. Fecal occult blood and histologic evidence of gastritis was associated with meloxicam administration in mice evaluated at days 4 and 8. By day 15, there was no association with meloxicam treatment and the presence of fecal occult blood or gastritis. There was no association between fecal occult blood and gastritis in the carprofen or saline-treated mice regardless of the treatment durations. These findings suggest that 20 mg/kg of meloxicam in mice causes gastric toxicity when given for 3 or 7 d and should be used cautiously; however, carprofen at 20 mg/kg appears to have minimal toxic effects with regard to the parameters measured.

Development of intestinal, but not gastric damage caused by a low dose of indomethacin in the presence of rofecoxib

The ulcerogenic effect of rofecoxib, a selective cyclooxygenase-2 (COX-2) inhibitor, on the gastrointestinal mucosa was investigated in the presence of a low dose of indomethacin. Indomethacin at 3 mg/kg did not cause any damage in both the stomach and small intestine, despite inhibiting prostaglandin (PG) production. Rofecoxib had no effect on PG production and did not cause any damage in these tissues. In the presence of indomethacin, however, rofecoxib provoked damage in the small intestine but not the stomach. Indomethacin at 3 mg/kg induced hypermotility and COX-2 expression in the intestine but not in the stomach, both in an atropine-sensitive manner. These results suggest that a low dose of indomethacin produces damage in the small intestine but not in the stomach when administered together with rofecoxib. The PG deficiency caused by a low dose of indomethacin produces hypermotility and COX-2 expression in the small intestine, and results in damage when COX-2 is inhibited. It is assumed that the hypermotility response is a key event in the expression of COX-2 and thereby important in the development of mucosal damage in the gastrointestinal tract.