Mode of Action

Blockade of Beta-1 receptors, primarily located in cardiac tissue, results in decreased heart rate, decreased contractility, slowed AV conduction, and suppression of automaticity.

Contraindications

Hypersensitivity to the particular beta blocker agent, cardiogenic shock or overt cardiac failure, severe sinus bradycardia, second and third degree heart block, bronchial asthma or chronic obstructive pulmonary disease.

Adverse Effects

Cardiac side effects include hypotension and bradycardia. CNS side effects include depression, headache, dizziness, and insomnia. Beta blockers may cause cholesterol abnormalities (increase in triglycerides and LDL, decrease in HDL). These agents may induce bronchospasm and antagonize the effects of bronchodilator medications (albuterol) used for the treatment of asthma. Beta blockers have been reported to cause sexual dysfunction, primarily decreased libido and impotence.

Drug-Drug Interactions

Concomitant use of beta blockers with alpha-1 antagonists may result in an exaggerated hypotensive response to the first dose of the alpha antagonist. This is due to suppression of the beta-mediated compensatory mechanism of increased heart rate in response to alpha blockade. Calcium channel blockers, digoxin, amiodarone, and quinidine may have additive cardiovascular effects when used in combination with beta blockers. The actions of beta-2 agonist medications (e.g., albuterol) may be antagonized, thus lessening their effectiveness. Hypotension may occur when beta blockers are used in conjunction with fentanyl anesthesia. 

Beta-adrenergic receptor blocking agents not only block the pulmonary effect of beta-agonists, such as VENTOLIN Inhalation Aerosol, but may produce severe bronchospasm in patients with asthma. Therefore, patients with asthma should not normally be treated with beta-blockers. However, under certain circumstances, e.g., as prophylaxis after myocardial infarction, there may be no acceptable alternatives to the use of beta-adrenergic blocking agents in patients with asthma. In this setting, cardioselective beta-blockers could be considered, although they should be administered with caution.