Albuterol

Overview

Selective beta-2 adrenergic receptor agonist. Relaxes bronchial smooth muscle by activating adenylyl cyclase, increasing intracellular cAMP, leading to bronchodilation.

Indications

Bronchospasm in asthma
Exercise-induced bronchospasm prevention
COPD (acute bronchospasm)
Hyperkalemia (off-label, drives potassium intracellularly)

Contraindications

Hypersensitivity to albuterol or any component

Classification

Respiratory Agents Bronchodilators Respiratory System

Mechanism of Action

Selective beta-2 adrenergic receptor agonist. Relaxes bronchial smooth muscle by activating adenylyl cyclase, increasing intracellular cAMP, leading to bronchodilation.

Pharmacodynamics

Short-acting beta-2 agonist (SABA). Onset 5-15 minutes (inhaled), duration 4-6 hours. Preferential effect on beta-2 receptors in bronchial smooth muscle vs beta-1 receptors in the heart at therapeutic doses.

Pharmacokinetics

Absorption: Inhaled: 10-20% reaches lower airways; remainder deposited in oropharynx and swallowed. Oral: well absorbed.
Distribution: Does not cross blood-brain barrier significantly.
Metabolism: Hepatic to inactive 4-O-sulfate metabolite.
Excretion: Renal (69-90% within 24 hours).
Half-life: 2.7-5 hours
Bioavailability: Inhaled: ~10-20% (lung deposition); Oral: ~50%
Protein Binding: 10%

Dosage

Typical dosage: MDI: 1-2 puffs (90-180 mcg) every 4-6 hours as needed. Nebulizer: 2.5mg 3-4 times daily.

Available Forms

Metered-dose inhaler (MDI)
Nebulization solution
Tablet
Syrup
Dry powder inhaler

Side Effects

Common

Tremor
Palpitations
Tachycardia
Nervousness
Headache

Serious

Paradoxical bronchospasm
Severe hypokalemia
Cardiac arrhythmias

Rare

Angioedema
Urticaria

Drug Interactions

major

Beta-blockers (especially non-selective like propranolol) antagonize bronchodilator effect and may cause severe bronchospasm in asthmatic patients.

moderate

Both albuterol and loop/thiazide diuretics can cause hypokalemia. Monitor potassium when used together.

Warnings

Pregnancy

Category C

Toxicity

LD50 >2000 mg/kg (oral, rat)

Overdose

Symptoms: exaggeration of side effects — tremor, tachycardia, hypokalemia, hyperglycemia, seizures. Treatment: cardioselective beta-blocker with caution, potassium supplementation, supportive care.

References

PMC4485508

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