Short-acting Beta-2 Agonist

Salbutamol

A short-acting beta-2 agonist used as a reliever inhaler in asthma and COPD, and by nebulizer in severe attacks.

Also called albuterol (US name).

Drug card

Class: Short-acting beta-2 agonist
How it works: Activating airway beta-2 receptors to relax bronchial muscle within minutes
Used for: Relief of asthma symptoms and attacks
Preventing exercise-induced bronchospasm
Relief of breathlessness in COPD
Known for: Shaky hands (tremor)
Fast heartbeat and palpitations

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Mechanism of action

How does salbutamol work?

A racemic mixture of R-salbutamol (levalbuterol) and S-salbutamol that acts preferentially on beta-2 receptors; the rise in cyclic AMP relaxes the smooth muscle of every airway, large and small, and reduces mediator release from mast cells. It also stimulates beta-1 receptors to a lesser degree, which adds to the faster heart rate.

Like other short-acting beta-2 agonists: SABAs stimulate the beta-2 receptors of airway smooth muscle. Through a G protein the receptor switches on adenylyl cyclase; the rise in cyclic AMP activates protein kinase A, which lowers calcium inside the cell and relaxes the muscle from the trachea down to the smallest bronchioles. Inhaled, they open the airways almost at once and work for 4 to 6 hours, so they serve as relievers.

Uses

What is salbutamol used for?

Relief of asthma symptoms and attacks
Preventing exercise-induced bronchospasm
Relief of breathlessness in COPD

Side effects

Side effects of salbutamol

Shaky hands (tremor)Known for
Fast heartbeat and palpitationsKnown for
Headache
Nervousness and sleeplessness
Muscle cramps
Low potassium (hypokalemia)Serious
Raised blood sugar
Atrial fibrillation and other arrhythmiasSerious
QT prolongation on the ECG
Paradoxical bronchospasmSerious
Throat irritation and hoarseness
Allergic reactions: hives, angioedemaSerious

Known for marks what an exam expects you to know it for.

Watch for

Cautions and what sets it apart

Needing it more often than usual signals worsening asthma that needs steroid treatment.
Beta blockers block its effect and can cause severe bronchospasm in asthma.
Diuretics, steroids and theophylline add to the fall in potassium.
Deaths have followed heavy overuse of inhaled sympathomimetics in severe asthma.

Good to know: With terbutaline it is one of the two main reliever inhalers: it works almost at once and lasts 4 to 6 hours.

Remember it

A way to remember it

Relievers rattle: shaky hands, racing heart.

Beta-2 stimulation opens the airways within minutes, but the commonest side effects are a tremor and a fast heartbeat, and potassium falls as it shifts into cells.

Written for biofideX

Its class

Short-acting beta-2 agonists

Other short-acting beta-2 agonists with a card:

Terbutaline

Easily mixed up with long-acting beta-2 agonists, inhaled antimuscarinics and beta blockers.

All about short-acting beta-2 agonists

Sources

Checked against

Written for biofideX in plain words, after checking these references:

For learning pharmacology, not for treatment decisions: no doses are given, and a prescriber, pharmacist or the product's own label is the word on any one patient. Spotted a mistake? Tell us and we'll correct it.

Practice it

Lungs and allergy

Salbutamol is one of 16 drugs practiced together here: their classes, how they work, what they treat and what they're known for.

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