Drug-drug interactions between antiarrhythmic drugs in chick embryos

The drug-drug interactions between antiarrhythmic drugs were studied in chick embryos. Fertilized eggs of White Leghorns were incubated and investigated. Procainamide or flecainide with and without propranolol was injected into the air sac of a fertilized egg. Electrocardiograms (ECGs) were recorded 0 to 60 min after the injection. After each drug injection alone, the heart rate was not different compared with the control. However, the heart rate was significantly decreased by combinations of procainamide and propranolol or flecainide and propranolol. In addition, arrhythmia was produced in combination with propranolol. These findings indicate that the drug-drug interactions between antiarrhythmic drugs have a marked influence on the heart rate in chick embryos.