Side effect of antihistamines in humans and animals are numerous and the most effects of these drugs that have been reported are cardiovascular effects such as ventricular fibrillation and death due to prolonged QT and abnormal ventricular arrythmies with some antihistamines. According to clinical applications fexofenadine and other antihistamines in control of atopic and allergic dermatitis in dogs and the importance of replacing antihistamine instead of corticosteroids.In present study first of all dogs electrocardiogram at day zero were obtained and then these dogs divided to two groups, in first group each dogs eat 3mg/kg BW (orally) fexofenadine for 7 consecutive days. In second group 18mg/kg Fexofenadine and fluconazole (orally) for 7 consecutive days were administrated. Immediately after the last dose, at times 0,2,6 and 8 hours after administration ECG were obtained of treated dogs. In the present study we observed that fexofenadine with all strength can decrease heart rate during times of 2, 6 and 8 hours after dosing which is followed by increase of factors like distance RR, PR and QT interval, finally results of this study induced bradycardia and decreased heart rate after orally administration of fexofenadine.Taking antihistamines, especially blockers H1 antihistamines should be done with caution in patients with heart decrease in dogs and dogs with heart worm disease and avoid using long time of these compounds and before using these drugs in dogs with atopic dermatitis, electrocardiogram is required for a healthy test, then fexofenadine is administrated.
