Name: Timolol (Blocadren)
Class: Nonselective b-Blocking Agent
Mechanism: Competitive blockade of b1 and b2 receptors. No a effect.
Absorption: Good oral (>90%). High bioavailability ~75%. Plasma levels vary 7x btwn. patients. b-blocking plasma conc. 5-10 ng/mL (low). Eye drops.
Dist.: 10% bound to protein. Excretion, t½: Hepatic, renal. Short t½ (3-4 hr).
Toxicity/S.E.s: CV—hypotension, bradycardia, c/i for CHF 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: Hypertension (¯ CO ® ¯ BP; blocks renin release). Angina pectoris (prophylactic ® exercise tolerance due to ¯ O2 demand). Cardiac arrhythmias (esp. supravent. tachyarrhyths). Acute MI (prophylaxis and reduction of infarct size and failure). Pheochromocytoma (in comb. w/alpha blocker). Essential tremor. Migraine headache (prophylaxis). Performance anxiety. Eyedrops for open-angle glaucoma (¯ production of aqueous humor).
Spec. Features: Abrupt w/drawal may trigger MI. 6-10x as potent orally as others.