Calcium channel blockers have become widely used in human and animal medicine. Different groups of these drugs are used routinely for treating cardiac arrhythmias, systemic hypertension and hypertrophic cardiomyopathy in small animals. The structural differences among these classes are associated with distinct binding sites on the "slow" calcium channel, resulting various potency and tissue affinities. Most currently available calcium channel antagonists exert their action on voltage operated, L-type channel within the plasma membrane. Blockade of L-type channel in vascular tissue results in the relaxation of vascular smooth muscle, and blockade of these channel in the cardiac tissue results in negative inotropic and chronotropic effects.

Verapamil is one of these drugs and used routinely in human and veterinary medicine. This agent blocks "slow" calcium channels in the cardiac.

In this research, we tried to determination of the induced electrocardiography changes with this drug. We selected one group with ten dogs. We never used any chemical drug for restraining because sedative drugs affects on normal cardiac function. We obtained an electrocardiogram to determinate any cardiac disorders and dogs with cardiac problems were eliminated. Different dosages resolved in NaCl (0.9%) with three different dilutions. Injectable drugs were calculated based on drop per minutes. According to the quick onset and half life of verapamil, we obtained electrocardiograms five minutes after injection. The injection interval of different solutions were seven hours. We used 0.01mg/kg/min for first injection and after 7 hours we continued with 0.02 and 0.03 mg/kg/min. After collection of data, we calculate these data with Repeated Measures ANOVA by SPSS 9.01.

Comparative study on normal electrocardiograms and after different injection of verapamil indicate only elevation of heart rates with no other visible changes on electrocardiogram ( just opposite result). Therefore, with attention to the effects and analyzing of statistic data indicate that verapamil is a safe drug ( on it's normal doses ) for treating of some arrhythmias ( like supraventricular tachyarrhythmias ) and seems to be an emergence drug for resolving of blood pressure and some arrhythmias. Furthermore, we know that verapamil is negative inotropic agent but use these dosages on normal dogs can stimulate haemostatic reaction because we see opposite effects on normal dogs. This elevation of heart rate may be induced by reduction of blood pressure (about 20 mmHg) and stimulation of compensatory reaction for adjustment of blood pressure.