Abstract
Summary
The influence of various cardio-depressant and beta adrenergic blocking drugs on the daunomycin induced bidirectional arrhythmia in the hamster was determined. Diphenylhydantoin reverted the arrhythmia to sinus rhythm with minimal decreases in heart rate and blood pressure. Quinidine exerted some antiarrhythmic activity but the resulting ECG patterns were not normal in most cases. In addition, the higher doses produced a persistant decrease in heart rate and blood pressure. These results support the evidence that the antiarrhythmic action of diphenylhydantoin is different from quinidine. Other quinidine-like agents such as lidocaine and procainamide exerted minimal antiarrhythmic activity. The most effective agent tested racemic propranolol antagonized the arrhythmia at lower doses than dexpropranolol although each isomer decreased heart rate. Both d(—)-INPEA and dl-MJ 1999 exerted almost no antiarrhythmic activity. These results tend to indicate that antagonism of the daunomycin arrhythmia is due to actions other than beta receptor blockade but in the case of racemic propranolol these actions are enhanced if simulataneous beta adrenergic receptor blockade also occurs.
The authors are grateful to the following suppliers of compounds: Dr. W. Murmann of Selvi and Company (Milano) for isomers of INPEA and Dr. Alex Sahagian Edwards of Ayerst Laboratories (New York) for isomers of propranolol.
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