Salbutamol activates adenyl cyclase, the enzyme that stimulates the production of cyclic adenosine-3', 5'-monophosphate (cAMP). Increased cAMP leads to activation of protein kinase A, which inhibits phosphorylation of myosin and lowers intracellular ionic Ca concentrations, resulting in smooth muscle relaxation.
Acute bronchospasm: 2-4 mg 3 or 4 times/day, up to 8 mg 3 or 4 times/day. As modified-release tab: 8 mg bid.
Severe bronchospasm - 50 mcg/mL soln: 250 mcg (4 mcg/kg) injected slowly. May be repeated if necessary. 10 mcg/mL soln: usual rate of 3-20 mcg/min (0.3-2 mL/min). Higher doses may be used in resp failure.
Severe bronchospasm: 500 mcg (8 mcg/kg) and repeated 4 hrly as required.
Acute bronchospasm - metered-dose aerosol or dry powd inhaler: 1 or 2 inhalations up to 4 times/day. Max: 800 mcg/day.
Prophylaxis of exercise-induced bronchospasm - metered-dose aerosol or dry powd inhaler: 2 inhalations 10-15 min prior to exercise.
Severe bronchospasm - via nebuliser: 2.5-5 mg, up to 4 times/day or, continuously at a rate of 1-2 mg/hr.
Acute severe asthma - metered-dose inhaler via spacer device. Initial: 4 inhalations, then a further 2 inhalations every 2 min according to response. Max: 10 inhalations.
Adverse drug reactions
: tremor, nervousness, nausea and vomiting, tachycardia, palpitations, chest pain, shakiness, dizziness, headache, insomnia, inhalation site sensation, hyperactivity, increased sweating, allergic reactions.
Adapted from CIMS Drug Information System. Internet. Accessed on January 10, 2016.