Beta-2 adrenergic agonists

β₂ adrenergic agonists are used in pulmonology as bronchodilators, in obstetrics as tocolytic agents, and to manage patients with hyperkalemia. There are both short-acting and long-acting β₂ agonists, and their duration of action determines their clinical application. Their effects are achieved through β₂ receptor stimulation. Side effects are partially mediated by the β₁ receptor and include anxiety and tremor, as well as life-threatening conditions such as ventricular arrhythmias.

• All β₂ adrenergic agonists selectively stimulate β₂ adrenergic receptors.
• Relax bronchial smooth muscle

• Cardiac: : ventricular arrhythmias; , vasoconstriction, angina pectoris, tachycardia, and palpitations; may aggravate cardiomyopathy in patients with cardiovascular disease
• Central nervous system/muscular: tremor, headache, anxiety, and sleep disturbances
• Electrolytes
  • Hyperglycemia
  • Hypokalemia (risk of life-threatening arrhythmias): β₂-mediated stimulation of Na⁺/K⁺-ATPase → intracellular K⁺ shift
• Development of tolerance

Paradoxical bronchospasm may occur!

References:^[1][2][3]

We list the most important adverse effects. The selection is not exhaustive.

• Bronchial asthma: used to achieve spasmolysis of the bronchi.
  • Acute exacerbation: use short-acting selective β₂-agonists (e.g., albuterol)
  • Prophylaxis (in chronic disease): use long-acting selective β₂-agonists (e.g., salmeterol)
• COPD: used to achieve spasmolysis of the bronchi.
• Preterm/undesired contractions in obstetrics: used for tocolysis
• Hyperkalemia: Beta-2 adrenergic agonists drive K⁺ intracellularly.

Salmeterol should not be used as monotherapy during an acute asthma attack!

References:^[1][2][4][5]

• Absolute contraindication: hypersensitivity to β2 adrenergic agonists
• Use with caution in patients with the following conditions:
  • Hyperthyroidism
  • Glaucoma
  • Diabetes
  • Hypokalemia
  • Seizures
  • Cardiovascular disease (e.g., heart failure, hypertension, arrhythmias, coronary artery disease)

We list the most important contraindications. The selection is not exhaustive.

• A face mask is recommended for children < 4 years on inhalational therapy.