Name: Propranolol (Inderal)
Class: Nonselective b-Blocking Agent
Mechanism: Competitive blockade of b1 and b2 receptors. No a effect. Decreases conversion of T4 to T3 by inhibiting hepatic monodeiodinase.
Absorp.: Good oral (>90%). Low bioavail.: ~30%. Plasma levels vary 20x btwn. patients.
Dist.:93% bound to protein. Enters CNS. Metabolism.: Hepatic Excret., t½: Short t½ (3.5-6 hr).
Toxicity/S.E.s: CV—hypotension, bradycardia, c/i for CHF[KLW1] or AV block. Resp—c/i in asthmatics, COPD, bronchitis, allergic rhinitis. Metabolism—caution w/diabetics (masks signs of hypoglycemia: tachycardia). CNS—weakness, fatigue, nightmares, depression. GI—n/v (uncommon). Hypersens—rash, hematologic disorders (rare).
Utility: Mild-mod HTN (¯ CO ® ¯ BP; blocks renin release). Adjunct to direct vasodilators for severe HTN (prevents reflex tachycardia). Angina pectoris (prophylactic ® exercise tolerance 2° ¯ O2 demand). Cardiac arrhythmias (esp. supravent. tachyarrhyths). Acute MI (prophylaxis & reduction of infarct size and failure). Pheochromocytoma (in comb. w/a -blocker). Essential tremor. Migraine headache (prophylaxis). Performance anxiety. Thyrotoxicosis—Suppression of signs/symptoms. Most effective drug for Rx of thyrotoxic crisis or thyroid storm (usu. in comb w/thioamide and/or iodide. Can be used preoperatively. Controversial Rx of hyperthyroid symptoms while awaiting effects of thioamides or iodide.
Special Features: Abrupt w/drawal may trigger MI.