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The Role of Beta Blockers in Graves' Disease

© Elaine Moore

While they are not used as a primary therapy in Graves’ disease, beta adrenergic antagonist drugs(beta blocker, beta adrenergic blocking agents)play an important role in treatment. Consequently, beta blockers are often prescribed as complementary therapeutic agents. Beta blockers are valuable in reducing and relieving both cardiac and nervous symptoms. Specifically, these drugs reduce anxiety, heart rate, palpitations, high blood pressure and alleviate migraines.

Although the beta blocker propranolol (Inderal) was the first drug of this class used to treat thyrotoxicosis, newer cardioselective agents such as esmolol, atenolol and metoprolol are widely prescribed today. However, propranolol is primarily used in Graves’ disease since it has the advantage of inhibiting the conversion of thyroxine (T4) to the more potent triiodothyronine (T3).

Although propranolol is contraindicated in patients with bronchospasm and asthma, cardioselective beta blockers such as metoprolol may be used in patients who have mild bronchial or asthmatic disorders. Beta blockers are also contraindicated in congestive heart failure except when the heart failure is rate related or caused by atrial fibrillation. In diabetes, beta blockers are contraindicated because they may mask hypoglycemic symptoms. Beta blockers should not be used in patients with bradyarrhythmias, Raynaud’s phenomenon or in patients who are taking monoamine oxidase (MAO)inhibitors.

Beta adrenergic antagonists are tolerated well by most Graves’ disease patients although at high doses they may cause drowsiness. Common side effects of beta adrenergic antagonists include nausea, headache, fatigue, insomnia and depression. Beta adrenergic antagonists, especially when used at high doses, must be not withdrawn abruptly. Abrupt withdrawal may be followed by an exacerbation of symptoms of hyperthyroidism, including thyroid storm. Other side effects include, skin rashes, drug related lupus, agranulocytosis, ischemic colitis, and Raynaud’s phenomenon.

Beta adrenergic blocking agents are almost completely absorbed from the gastrointestinal tract, although a portion is immediately bound by the liver. Peak effects of propranolol occur in one to one and one-half hours, and the biologic half life of this drug is four hours. Propranolol is indicated for the long-term management of patients with hypertension, cardiac arrhythmias, ventricular tachycardias, essential tremor, hypertrophic subaortic stenosis, migraines, and as adjunctive therapy in patients with pheochromocytoma.

Because beta adrenergic blocking agents inhibit sympathetic circulation, they are contraindicated in patients with congestive heart failure. Beta blockers should also be used with caution in patients with impaired hepatic or renal function. Beta blockers may also reduce intraocular pressure and may interfere with tests for glaucoma screening.

Drugs that compete with the absorption of beta blockers in the gut, thereby reducing their effects, include aluminum hydroxide, ethanol, chlorpromazine, and cimetidine.