Final answer:
The generic name for the drug Procanbid is procainamide, which is an antiarrhythmic medication, distinct from β-blockers like Atenolol, Metoprolol, and Propranolol.
Step-by-step explanation:
The generic name of the drug Procanbid is procainamide. The medications listed in the question such as Atenolol, Metoprolol, and Propranolol are all β-blockers, which are used to treat cardiovascular diseases by blocking β-receptors in the heart that are associated with vasoconstriction and cardioacceleration.
Their mechanism of action involves preventing adrenaline from increasing the heart rate and causing the blood vessels to constrict, thereby improving cardiac function. However, Procainamide is different as it is not a β-blocker but an antiarrhythmic medication used to treat certain types of serious irregular heartbeats.