Introduction
Salbutamol (also known as albuterol in the United States) is a short-acting β2-adrenergic receptor agonist (SABA) medication primarily used as a bronchodilator for the management of reversible airway obstruction. First introduced in the 1960s, it remains a cornerstone therapy in asthma and chronic obstructive pulmonary disease (COPD) management worldwide. This fast-acting medication provides rapid relief of bronchospasm and is available in various formulations including metered-dose inhalers, dry powder inhalers, nebulizer solutions, and oral preparations.
Mechanism of Action
Salbutamol selectively stimulates β2-adrenergic receptors in bronchial smooth muscle, leading to activation of adenylate cyclase and increased intracellular cyclic AMP. This results in relaxation of bronchial smooth muscle, inhibition of mast cell mediator release, and stimulation of mucociliary clearance. The drug has minimal β1-adrenergic activity at therapeutic doses, resulting in fewer cardiac effects compared to non-selective beta-agonists.
Indications
- Relief of acute bronchospasm in reversible obstructive airway disease (asthma, COPD)
- Prevention of exercise-induced bronchospasm
- Management of acute exacerbations of asthma and COPD
- Adjunctive therapy in the management of hyperkalemia (off-label)
- Tocolytic therapy for premature labor (off-label, though other β2-agonists are preferred)
Dosage and Administration
Inhalation (MDI):- Adults: 1-2 inhalations (90-180 mcg) every 4-6 hours as needed
- Children: 1 inhalation (90 mcg) every 4-6 hours as needed
- Adults: 2.5 mg every 4-6 hours as needed
- Children: 0.63-1.25 mg every 4-6 hours as needed
- Hepatic impairment: No dosage adjustment required
- Renal impairment: No dosage adjustment required
- Elderly: Use with caution due to increased cardiac risk
- Pregnancy: Category C; use if clearly needed
Pharmacokinetics
Absorption: Rapidly absorbed following inhalation with onset of action within 5-15 minutes. Oral bioavailability is approximately 50% but is associated with more systemic effects. Distribution: Distributed throughout the body with minimal plasma protein binding (10%). Metabolism: Extensively metabolized in the liver to inactive sulfate conjugates. Elimination: Primarily excreted in urine (60-80% within 24 hours) with an elimination half-life of 3.8-6 hours.Contraindications
- Hypersensitivity to salbutamol or any component of the formulation
- Tachyarrhythmias
- History of hypersensitivity reactions to sympathomimetic amines
Warnings and Precautions
- Paradoxical bronchospasm: Can occur and requires immediate discontinuation
- Cardiovascular effects: May cause tachycardia, hypertension, and arrhythmias
- Hypokalemia: Can cause clinically significant decreases in serum potassium
- Diabetes: May increase blood glucose levels
- Seizure disorders: May lower seizure threshold
- Thyrotoxicosis: May aggravate symptoms
Drug Interactions
- Beta-blockers: May antagonize bronchodilator effects (non-selective beta-blockers)
- Diuretics: Enhanced hypokalemic effects
- Digoxin: Increased risk of arrhythmias with hypokalemia
- MAO inhibitors and tricyclic antidepressants: May potentiate cardiovascular effects
- Other sympathomimetics: Additive cardiovascular effects
Adverse Effects
Common (>10%):- Tremor
- Headache
- Tachycardia
- Palpitations
- Nervousness
- Muscle cramps
- Dizziness
- Nausea
- Cough
- Throat irritation
- Paradoxical bronchospasm
- Angina
- Hypokalemia
- Allergic reactions including anaphylaxis
- Cardiac arrhythmias
Monitoring Parameters
- Pulmonary function (FEV1, peak flow)
- Heart rate and rhythm
- Blood pressure
- Serum potassium levels (with frequent use)
- Blood glucose in diabetic patients
- Therapeutic response and symptom control
- Inhaler technique assessment
Patient Education
- Use only as directed for acute symptom relief
- Prime inhaler before first use or if not used for 2 weeks
- Shake inhaler well before each use
- Rinse mouth after inhalation to prevent thrush
- Seek medical attention if symptoms worsen or require more frequent use
- Do not exceed recommended dosage
- Keep rescue inhaler readily accessible at all times
- Understand difference between rescue and controller medications
- Report any chest pain, palpitations, or tremors to healthcare provider
- Have a written asthma action plan
References
1. Global Initiative for Asthma (GINA). Global Strategy for Asthma Management and Prevention, 2023. 2. Global Initiative for Chronic Obstructive Lung Disease (GOLD). Global Strategy for the Diagnosis, Management, and Prevention of Chronic Obstructive Pulmonary Disease, 2023. 3. National Heart, Lung, and Blood Institute. Expert Panel Report 3: Guidelines for the Diagnosis and Management of Asthma, 2007. 4. Lexicomp Online. Albuterol monograph. Wolters Kluwer Clinical Drug Information, 2023. 5. Micromedex Solutions. Albuterol drug monograph. IBM Watson Health, 2023. 6. FDA prescribing information: Ventolin HFA (albuterol sulfate inhalation aerosol), 2022. 7. Barnes PJ. Pulmonary pharmacology. In: Brunton LL, Hilal-Dandan R, Knollmann BC, eds. Goodman & Gilman's The Pharmacological Basis of Therapeutics. 13th ed. McGraw-Hill; 2017. 8. Cazzola M, Calzetta L, Matera MG. β2-adrenoceptor agonists: current and future direction. Br J Pharmacol. 2011;163(1):4-17.