Pulmonology · USMLE Step 1 and Step 2

Beta-2 Agonists - SABA & LABA song

SABA vs LABA - Mechanism & Side Effects, as a song. Hear the short teaser here. The full song is on YouTube and Spotify.

Beta-2 Agonists - SABA & LABA

Full song on YouTube ↗Spotify ↗

Key points in this song10

Beta-2 agonists activate Gs-coupled receptors, increasing cAMP via adenylyl cyclase, which activates PKA, leading to smooth muscle relaxation and bronchodilation.
Short-acting beta-2 agonists (SABAs) such as albuterol and levalbuterol are the first-line rescue therapy for acute bronchospasm in asthma and COPD exacerbations.
Long-acting beta-2 agonists (LABAs) such as salmeterol and formoterol are used for maintenance therapy and must never be used as monotherapy in asthma due to increased risk of asthma-related death.
LABAs are always combined with inhaled corticosteroids (ICS) in asthma management; this combination (e.g., fluticasone/salmeterol) improves symptom control without the mortality risk of LABA monotherapy.
Albuterol causes hypokalemia by driving potassium into cells via Na-K-ATPase stimulation, making it a treatment option for acute hyperkalemia.
Beta-2 agonists cause tachycardia and tremor as common side effects due to residual beta-1 activity and skeletal muscle receptor stimulation, respectively.
Salmeterol has an exceptionally long duration of action (12 hours) due to its lipophilic side chain anchoring it near the receptor, while formoterol is also long-acting but has a faster onset.
Beta-2 agonists are used as tocolytics (e.g., terbutaline) to inhibit premature uterine contractions by relaxing uterine smooth muscle.
Overuse of SABAs (more than 2 days per week) indicates poorly controlled asthma and signals the need to step up therapy per NAEPP guidelines.
Beta-2 agonists cause bronchodilation but do not address underlying airway inflammation, which is why corticosteroids remain the cornerstone of long-term asthma control.