The present study aimed at shedding some light on the pharmacological effects of two NSAIDs (one selective, that is meloxicam, and the other is non-selective, that is piroxicam) on cardiac contractility and aortic smooth muscle of rabbit as a farm animal species. Rhythmic contractions of the heart were established using Gunn’s apparatus (heart infusion assembly) and normal tone of the aortic rings was established using tension recording technique. The effects of graded increased concentrations of piroxicam and meloxicam on the installed organs were studied. The sites of action of piroxicam and meloxicam were also tried. The obtained results proved that piroxicam and meloxicam had concentration-dependant, negative inotropic and chronotropic effects on the rabbit's heart; and were without significant effects on aortic rings throughout the tested concentrations. The effects of piroxicam and meloxicam on the heart were not affected by pre-addition of atropine, and the effect of adrenaline was evident in presence of the tested drugs indicating the non-involvement of cholinergic and adrenergic pathways in their mechanism of action. The effects of the drugs might be then attributed to their direct effect on the cardiac myocytes probably via decreasing Ca2+ concentration. 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 myocardial contractility that should be taken in consideration in case of introducing these drugs in therapy with larger doses. |
