Use caution with history of severe anaphylaxis to allergens. Treatment of anaphylaxis (e.g. epinephrine) in patients taking β-blockers may be ineffective or promote undesirable effects. In general, patients with bronchospastic disease should not receive β-blockers. Consider pre-existing conditions such as sick sinus syndrome before initiating. Use with caution in the following cases: diabetes mellitus (may potentiate hypoglycemia and/or mask signs and symptoms), compensated heart failure, hepatic impairment, myasthenia gravis, peripheral vascular disease (including Raynaud’s), renal impairment (may have increased side-effects). Use with caution in history of psychiatric illness (may cause or exacerbate CNS depression). β-blockade may mask signs of hyperthyroidism (e.g. tachycardia). Abrupt discontinuation of β-blockade may exacerbate symptoms of hyperthyroidism and may also induce thyroid storm. Use with caution in patients receiving anesthetic agents which decrease myocardial function (e.g. ether, cyclopropane and trichloroethylene). Use with caution in patients on concurrent verapamil or diltiazem (bradycardia or heart block can occur). β-blocker therapy should not be withdrawn abruptly (particularly in coronary artery disease). Smoking may decrease plasma levels of propranolol by increasing metabolism.