Effects of non-selective (piroxicam) and selective (meloxicam) cyclo-oxygenase inhibitors on the intestinal contractility of rabbits

Abstract

Background: To shed some light on full characterization and utilization of non-steroidal anti-inflammatory drugs (NSAIDs) in veterinary medicine, this study, therefore, was designed to clarify the pharmacological effects of two NSAIDs (one selective, that is meloxicam, and the other is non-selective, that is piroxicam) on intestinal contractility of rabbit as a farm animal species. Methods: Rabbits were humanely slaughtered, and segments from different parts of intestinal tracts were dissected out and an intestinal segment of about 2 cm long was fixed in an organ bath containing warm oxygenated Tyrode’s solution at 37°C. The tissue was subjected to a resting tension of 2 g and allowed to equilibrate for 30 min and then the effects of graded increased concentrations of piroxicam and meloxicam were demonstrated on the normal rhythmic motility of the isolated intestinal segments. The sites of action of piroxicam and meloxicam were tried. Results: Piroxicam and meloxicam exhibited concentration-dependent relaxations of intestinal smooth muscle segments with minimal and maximal effects of more potency by prioxicam than meloxicam. Calculated inhibitory concentration 50% were 15.45 and 23.10 μg/ml bath for piroxicam and meloxicam, respectively. Effects of either piroxicam or meloxicam did not involve cholinergic, adrenergic, histaminergic, nitrergic, or purinergic pathways as the application of the corresponding agonists/antagonists did not affect the inhibitory response of piroxicam and meloxicam. It was assumed that the effects of the drugs were attributed to the direct effects of the drugs on the intestines in addition to inhibiting endogenous prostaglandin synthesis activity via their cyclo-oxygenase inhibiting properties. Conclusions: Data of the present study may indicate that piroxicam and meloxicam could be used effectively and safely in rabbits for their anti-inflammatory actions in small therapeutic doses. However, in large doses, they (particularly, piroxicam) may produce depressant effects on gastrointestinal tract motility that should be taken in consideration in the case of introducing these drugs in therapy with larger doses.