Salbutamol

What it is

Salbutamol (albuterol in the US) is the most widely used reliever bronchodilator in the world. It is a short-acting beta-2 agonist (SABA) that relaxes bronchial smooth muscle within minutes, and it is essential in the treatment of asthma and COPD.

In Spain it is supplied on prescription. Frequent use (more than twice a week) means poorly controlled asthma and should be reported to the doctor so the maintenance treatment can be reviewed.

Selective stimulation of the bronchial beta-2 adrenergic receptor

Salbutamol acts on the beta-2 receptors of bronchial smooth muscle:

• It binds to β2 adrenergic receptors in bronchial smooth muscle → it activates adenylate cyclase → it increases intracellular cAMP.
• cAMP activates protein kinase A → it phosphorylates myosin light-chain kinase → bronchial smooth muscle relaxes.
• Rapid bronchodilation: onset in 3–5 minutes, maximum effect at 15–30 minutes, duration 4–6 hours.
• β2 selectivity: at normal doses, minimal effect on cardiac β1 receptors (although it is not absolute).
• It also stabilises mast cells and reduces the release of inflammatory mediators.

At the counter

When to recommend it

• Supply on prescription
• Check the inhaler technique at every supply: it is the most important factor for efficacy
• Explain that it is a RELIEVER: for quick relief of symptoms, not for daily preventive use
• If the patient uses the inhaler more than twice a week: a sign of poorly controlled asthma, refer to the doctor
• Check that they also have a maintenance inhaler (inhaled corticosteroid)

When not to

• Do not replace the maintenance treatment (inhaled corticosteroid): salbutamol treats bronchospasm but not the underlying inflammation
• Do not use it as the only treatment in any asthma: the guidelines (GINA) always call for an inhaled corticosteroid
• Caution with tachyarrhythmias: residual β1 stimulation can raise the heart rate
• Do not use it out of date: the propellant may fail in expired MDI inhalers

Warnings

• Important SEVERE ASTHMA ATTACK: if salbutamol does not relieve the attack within 15–20 minutes or the symptoms are severe (breathless at rest, unable to talk), call the emergency number at once (112 in Spain). Salbutamol is the first step but not enough in severe attacks.
• Caution TACHYCARDIA: salbutamol can cause tachycardia, tremor, nervousness and low potassium (especially at high doses or nebulised). In patients with heart disease, keep watch.
• Caution LOW POTASSIUM: at high doses, salbutamol shifts potassium into the cells, lowering blood potassium. Especially relevant if the patient also takes systemic corticosteroids or diuretics.
• Caution OVERUSE: frequent salbutamol use without maintenance treatment can mask poorly controlled asthma and increase the risk of severe attacks. More than 2 uses a week = see the doctor.
• Worth knowing PREGNANCY: inhaled salbutamol at usual doses is considered safe in pregnancy. Uncontrolled asthma is far more dangerous for the baby than the treatment.