Description & Key Indications: Albuterol is a short-acting beta-2 agonist (SABA) used as an inhaled bronchodilating agent. It treats acute bronchospasm and episodic wheezing in asthma, exercise-induced bronchospasm (EIB) prophylaxis, and serves as reliever therapy in COPD. Off-label uses include hyperkalemia, where it lowers potassium by 1–1.5 mEq/L, and managing respiratory symptoms in anaphylaxis unresponsive to epinephrine. Inhaled albuterol is preferred over oral routes due to its superior side-effect profile and faster onset.
Mechanism of Action: As a racemic mixture, bronchodilation is driven by the R-isomer (levalbuterol); the S-isomer exhibits bronchoconstrictive properties in animals. Albuterol stimulates moderately selective beta-2 receptors, activating adenylate cyclase to increase intracellular cyclic AMP. This triggers protein kinase A, inhibiting myosin phosphorylation and lowering calcium to relax bronchial smooth muscle. It also inhibits mast cell degranulation and drives potassium intracellularly via the Na/K ATPase pump.
Crucial Safety & Adverse Effects: Inhalation avoids many systemic issues, but severe reactions can occur, including paradoxical bronchospasm, arrhythmia, atrial fibrillation, Stevens-Johnson syndrome, and anaphylactoid reactions. Common mild-to-moderate effects include tremors (to 37.9%), infections (to 21%), headaches, rhinitis, tachycardia, palpitations, hypokalemia, and excitability.
Remaining 80% (Administration, Dosages & Pharmacokinetics)
Administration Techniques: Inhalation methods include metered-dose inhalers (MDIs), dry powder inhalers (DPIs), and nebulizers. MDIs require shaking, priming, and slow inhalation, followed by a 10-second breath hold; spacers or valved holding chambers (VHC) are recommended for pediatric and uncoordinated patients. For pediatric acute asthma, MDI with a VHC is as effective as nebulization. DPIs (e.g., RespiClick) are breath-activated upon opening the cap and must remain dry at all times. Nebulized solution is delivered over 5 to 15 minutes; "blow-by" is discouraged.
Dosing Standards: For acute asthma exacerbations, adults and children age 6 and older inhale 360–900 mcg via MDI every 20 minutes for the first hour, then every 1 to 4 hours as needed. EIB prophylaxis requires 180 mcg inhaled 15–30 minutes before exercise. Oral doses range from 2–4 mg 3–4 times daily, but guidelines discourage this route due to slow onset and systemic side effects.
Pharmacokinetics: Inhaled albuterol works within 5–15 minutes, peaks in 0.5–2 hours, and lasts 2–6 hours, with 90% of the dose typically swallowed. Oral immediate-release onset is 30 minutes, lasting 4–6 hours, while extended-release lasts 8–12 hours. Metabolism is hepatic, and excretion is primarily renal.
