Salbutamol
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Missing image Albuterol.png Molecular structure of salbutamol Salbutamol | |
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(R,S)-2-(1,1-dimethylethyl)amino- | |
| Empirical formula | C13H22N1O5 |
| Molecular weight | 239.3 |
| Bioavailability (Oral) | "well absorbed" |
| Metabolism | hepatic |
| Elimination half life (Oral/inhaled) | 2.7-5 hours |
| Excretion | renal |
| Pregnancy category | A (Australia) |
Salbutamol (INN) or albuterol (USAN) is a short-acting β2-adrenergic receptor agonist used for the relief of bronchospasm in conditions such as asthma and COPD. It is marketed by the Allen & Hanbury's respiratory division of GlaxoSmithKline under the trade name Ventolin. The name Albuterol comes from Salbutamol aersol.
Salbutamol sulfate is usually given by the inhaled route for direct effect on bronchial smooth muscle. This is usually achieved through a metered-dose inhaler (MDI) or nebuliser; but other delivery devices marketed for salbutamol sulfate include the Rotahaler, Diskhaler, and Autohaler. Salbutamol can also be given orally or intravenously.
Ventolin became available in the United Kingdom in 1969 and in the United States in 1980.
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Clinical use
Salbutamol is specifically indicated in the following conditions:
- acute asthma
- symptom relief during maintenance therapy of asthma and other conditions with reversible airways obstruction (including COPD)
- protection against exercise-induced asthma
- certain conditions involving hyperkalemia
As a β2-agonist, salbutamol also finds use in obstetrics. Intravenous salbutamol can be used as a tocolytic to relax the uterine smooth muscle to delay premature labour. Whilst preferred over agents such as atosiban and ritodrine, its role has largely been replaced by the calcium-channel blocker nifedipine which is more effective, better tolerated and orally effective. (Rossi, 2004)
Mode of action
As with other β2-adrenergic receptor agonists, salbutamol binds to β2-adrenergic receptors with a higher affinity than β1-receptors. In the airways, activation of β2-receptors results in relaxation of bronchial smooth muscle. resulting in a widening of the airway (bronchodilation). Inhaled salbutamol sulfate has a rapid onset of action, providing relief within 5-15 minutes of administration.
In tocolysis, the activation of β2-receptors results in relaxation of uterine smooth muscle, thus delaying labour.
Adverse effects
Whilst salbutamol is well-tolerated, particularly when compared with previous therapies such as theophylline, like all medications there exists the potential for adverse drug reactions to occur - especially when in high doses, or when taken orally or intravenously.
Common adverse effects include: tremor, palpitations and headache. (Rossi, 2004)
Infrequent adverse effects include: tachycardia, muscle cramps, agitation, hypokalemia, hyperactivity in children, and insomnia. (Rossi, 2004)
References
- Rossi S (Ed.) (2004). Australian Medicines Handbook 2004 (AMH). Adelaide: Australian Medicines Handbook. ISBN 0-9578521-4-2.