qq - honey91

[ArchivalUser]

correct answer is A


Beta-blockers, such as propranolol, labetalol, and pindolol, have membrane stabilizing effects (eg, quinidinelike effects).

This property, usually not evident with therapeutic doses, may significantly contribute to toxicity by prolonging QRS duration and impairing cardiac conduction.

Seizures are more commonly observed in the drugs with quinidine like membrane stabilizing effects

[ArchivalUser]

Antiarrhythmic means IA class=membrane stabilizing effect
The antiarrhythmic medicines of this class (Moracizine, procainamide, quinidine and other) effectively block rapid transmembrane Na+- channels and they, therefore, impede the maximum speed of diastolic depolarization (phase of 0 action potential), they displace the threshold potential of the membrane to the more positive level, moderately increase effective refractory period; therefore cardiomyocytes become less excited. Basic electrophysiological properties antiarrhythmics of IA class are given in the table. Besides this antiarrhythmics of IA class block the voltage-sensitive K+- channels and lengthen the effective refractory period of cardiomyocytes in essence due to lengthening of the phase of 3 repolarizations, and they also detain the restoration of the activity of rapid transmembrane Na+- channels, which entails lengthening action potential.

The preparations of this group suppress anomalous automatism, slow down the velocity of propagation of pulses along the heart muscle, including along the system of His fibers Purkinje.