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Dihydropyridines such as amlodipine and nifedipine act mainly on vascular smooth muscle, producing arteriolar vasodilation. Non-dihydropyridines, including verapamil and diltiazem, have greater effects on the SA and AV nodes and myocardium, slowing heart rate and conduction and reducing contractility. CCBs are used for essential hypertension and also have roles in conditions such as angina and arrhythmias; specific agents have additional uses. Their different actions inform their adverse-effect profiles: edema and flushing are associated with dihydropyridines, while non-dihydropyridines may cause bradycardia, AV block, constipation, or worsening heart failure. The full topic also addresses interactions, contraindications, overdose management, and withdrawal considerations.