RESULTS
Two-stage coronary ligation-induced arrhythmia: After one to two days of coronary ligation, all dogs continued to have multifocal VT. Arrhythmia was suppressed only by intravenous amiodarone , but other new class III drugs had neither antiarrhythmic nor proarrhythmic effects , as shown in Table 1. The consistent change by class III drugs was a decrease in the atrial rate only, indicating a direct negative chronotropic effect of class III drugs on the sinus node. Digitalis-induced arrhythmia: After a cumulative intravenous injection of about 40 to 80 |J.g/kg ouabain, almost all the beats became ventricular in origin. The arrhythmia was suppressed by intravenous amiodarone , but all other class III drugs had no antiarrhythmic effect , except dofetilide . Dofetilide at a very high dose of 100 |J.g/kg/10 mins induced VF in two of 11 dogs, but suppressed it in five others . Sematilide at a high dose of 3 mg/kg aggravated this arrhythmia , as shown in Table 1. Buy quality medications online: find sale viagra online every time you need treatment.

TABLE 1 Summary of the effects of class III drugs on canine ventricular arrhythmias

Arrhythmia induced by:
Class III drug Coronary Halothane- Reperfusion Reperfusion 24 h ECG- 24 h ECG-
Digitalis ligation adrenaline VF-halothane VF-PB PES control old MI
Amiodarone iv E(3 mg/kg) E(5 mg/kg) E(5 mg/kg) not E (6.7 mg/kg/h)
Amiodarone po not E (20 mg/kg/2W)
D-sotalol iv not E not E not E not E (15 E (10
(1 mg/kg) (1 mg/kg) (1 mg/kg) mg/kg/h) mg/kg/h)
E-4031 iv not E(1 mg/kg) not E(1 mg/kg) Agg (0.3 mg/kg) E (0.03 mg/kg +0.003 mg/kg/h)
MS-551 iv not E not E E (3.6 mg/kg/h) E (3.6 E AVC (100 PVC (100
(10 mg/kg) (10 mg/kg) mg/kg/h) (1 mg/kg) mg/kg po) mg/kg po)
Sematilide iv Agg not E Agg not E (3 mg/kg) not E E AVC (100 PVC (100
(3 mg/kg) (3 mg/kg) (1 mg/kg) (6 mg/kg) (3 mg/kg) mg/kg po) mg/kg po)
Dofetilide iv Agg/not E/E not E not E not E (0.1 not E E AVC (10 PVC (10
(0.1 mg/kg) (0.1 mg/kg) (0.1 mg/kg) mg/kg) (0.1 mg/kg) (0.1 mg/kg) mg/kg po) mg/kg po)
KCB 328 not E/E not E/E not E (1 E E (0.5 AVC (30
(1 mg/kg) (1 mg/kg) mg/kg/h) (1 mg/kg/h) mg/kg/h) mg/kg po)

Agg Aggravated; AVC Aberrant ventricular contraction; E Effective; ECG Electrocardiogram; iv Intravenous; MI Myocardial infarction; PB Pentobarbital; PES Programmed electrical stimulation used to induce arrhythmia in dogs with ‘old’ myocardial infarction; po Oral; PVC Premature ventricular complex; VF Ventricular fibrillation