Propranolol is a nonselective beta-adrenergic antagonist that blocks beta-1 receptors in the heart and beta-2 receptors in vascular and bronchial smooth muscle. It lowers heart rate, myocardial contractility, and renin release, reducing blood pressure and cardiac workload. In infantile hemangioma, beta blockade causes vasoconstriction, downregulates pro-angiogenic factors (VEGF, bFGF), and induces endothelial apoptosis leading to accelerated involution.