Albuterol
Albuterol
Generic Name
Albuterol
Mechanism
- β₂‑Receptor Agonist
- β₂ receptors on bronchial smooth‑muscle → ↑cyclic‑AMP → protein kinase A activation
- Phosphorylation of myosin light‑chain kinase → inhibition of calmodulin‑dependent contraction
- Result: rapid, reversible bronchodilation (onset ≤ 5 min, peak 10–15 min)
Pharmacokinetics
| Phase | Route | Key Points |
| Inhaled (nebulizer or DPI) | • Rapid pulmonary deposition |
• Onset 5–15 min, duration 4–6 h • Systemic absorption < 20 % of dose |
| Oral | • First‑pass hepatic metabolism |
• Poor bioavailability (≈ 10 %) • Longer half‑life (~2–4 h) but not clinically preferred for acute therapy |
| Excretion | • Renally cleared | • Elimination half‑life ~3–5 h (inhaled) |
| Metabolism | • Cytochrome P450 2D6 (minor) | • Minimal drug‑drug interactions |
Indications
- Acute bronchospasm in asthma and COPD
- Chronic maintenance bronchodilation (step‑up in milder disease)
- Exercise‑induced bronchoconstriction prophylaxis
- Reversible airway obstruction in critical‑care settings
Contraindications
| Category | Details |
| Absolute Contraindications | • Severe hypotension or uncontrolled hypertension (risk of vasospasm) |
| Relative Contraindications |
• Severe cardiac arrhythmias (tachyarrhythmias, LBBB) • Diabetes mellitus (hypoglycemia risk) • Hyperkalemia (β₂ agonists shift K⁺ intracellularly, worsening) |
| Warnings |
• Use with caution in pregnancy (Class B) • Potential for paradoxical bronchospasm (rare) |
| Precautions |
• Monitor electrolytes in patients with renal impairment • Avoid when using simultaneous β₁ agonists or adrenergic stimulants |
Dosing
| Formulation | Adult | Pediatric (≤ 5 yrs) | Special Device |
| Metered‑Dose Inhaler (MDI) | 2 puffs (90 µg each) q4–6 h PRN (max 12 puffs/24 h) | 1 puff q4–6 h (age‑adjusted) | Use spacer to improve pulmonary deposition |
| Dry Powder Inhaler (DPI) | 1 actuation (90 µg) q4–6 h | 1 actuation (age‑adjusted) | Ensure adequate inspiratory flow (≥ 30 L/min) |
| Nebulizer (Liquid) | 2.5–5 mg (0.25–0.5 mL of 2.5 mg/mL) q4–6 h | 0.25 mg/kg q4–6 h (max 5 mg) | Hourly for exacerbations |
| Sublingual | 400 µg (1 spray) q4–6 h | – | Alternative for patients unable to use inhaler |
*All dosing above is for acute use; maintenance regimens differ (e.g., long‑acting β₂ agonists).*
Adverse Effects
- Common (≥ 2 %)
- Tremor, palpitations, tachycardia, headache
- Throat irritation, cough, dehydration (especially in children)
- Hypokalemia (symptoms: muscle cramps, arrhythmias)
- Serious (< 0.1 %)
- Paradoxical bronchospasm – sudden worsening of airway resistance
- Severe arrhythmias (premature beats, AV block) in susceptible patients
- Hyponatremia in critical‑care patients (when combined with hyperoxia)
Monitoring
- Respiratory – peak expiratory flow (PEF) or spirometry if feasible
- Cardiac – pulse, rhythm, blood pressure (especially on high doses)
- Electrolytes – serum potassium (particularly in diabetics, renal disease)
- Blood glucose – if concomitant insulin or sulfonylureas
- Adverse effects – tremor, anxiety, insomnia (monitor for over‑use)
Clinical Pearls
- Spacer Use – Reduces extrathoracic deposition; improves lung delivery by ~30 %.
- Dose Limitation – Do not exceed 30 puffs (MDI) or 12 mg in 24 h, even if symptoms persist.
- Hyperkalemia Risk – In patients with renal insufficiency or potassium‑sparing diuretics, check K⁺ before and during therapy.
- Diabetic Patient – β₂ agonists can mask hypoglycemia—encourage frequent glucose checks.
- Nebulization in Pediatrics – Weight‑based dosing (0.25 mg/kg) ensures safety while still effective.
- Long‑Term Use – Use in combination with inhaled corticosteroids for chronic management; avoid monotherapy with long‑acting β₂ agonists due to asthma‑related mortality risk.
- Storage – Keep MDIs upright at room temperature; avoid excessive agitation to preserve propellant.
*These guidelines reflect consensus from major pharmacology and pulmonology references (e.g., Goodman & Gilman's, ATS/ERS statements).*
---