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RESPIRATORY SYSTEM › DRUGS FOR OBSTRUCTIVE AIRWAY DISEASES › ADRENERGICS, INHALANTS › Selective beta-2-adrenoreceptor agonists
clenbuterol
R03AC14
Forms & Strengths
- Oral tablets: 20 mcg
- Oral syrup: 5 mcg/mL
- Inhalation aerosol: 0.02 mg/actuation
Adult Dosing
- Bronchospasm: 20 mcg orally twice daily, may increase up to 40 mcg twice daily if necessary
- Asthma (maintenance): 20 to 40 mcg orally twice daily
Pediatric Dosing
- Children 12 years and older: 20 mcg orally twice daily
- Children under 12 years: Safety and efficacy not well established; typically 1.2 mcg/kg/day divided in 2 doses if used off-label
Indications
- Bronchospasm associated with chronic obstructive pulmonary disease (COPD)
- Asthma bronchiale
- Off-label: Athletic performance enhancement and weight loss (misuse)
Mechanism of Action
- Long-acting selective beta-2 adrenergic receptor agonist
- Stimulates adenylate cyclase, increasing intracellular cAMP
- Relaxes bronchial smooth muscle and inhibits release of immediate hypersensitivity mediators from mast cells
Contraindications
- Hypersensitivity to clenbuterol or sympathomimetic amines
- Hypertrophic obstructive cardiomyopathy (HOCM)
- Tachyarrhythmias
- First trimester of pregnancy
Adverse Reactions
- Tremors (particularly of the hands)
- Tachycardia and palpitations
- Headache
- Muscle cramps
- Nervousness, anxiety, and insomnia
- Hypokalemia and hyperglycemia at high doses
Drug Interactions
- Beta-blockers (e.g., propranolol) antagonize bronchodilatory effects and may induce severe bronchospasm
- MAO inhibitors and tricyclic antidepressants potentiate cardiovascular toxicity
- Other sympathomimetics increase risk of cardiovascular adverse effects
- Potassium-depleting diuretics (e.g., thiazides, furosemide) increase risk of severe hypokalemia
Curated Content: Needs Vetting Before Put to Clinical Use