salbutamol

Salbutamol
Systematic (IUPAC) name
2-(hydroxymethyl)-4-[1-hydroxy- 2-(tert-butylamino)ethyl]phenol
Identifiers
CAS number	18559-94-9
ATC code	R03AC02 R03CC02
PubChem	2083
DrugBank	APRD00553
Chemical data
Formula	C13H21NO3
Mol. mass	239.311
SMILES	search in eMolecules, PubChem
Pharmacokinetic data
Bioavailability	?
Metabolism	Hepatic
Half life	1.6 hours
Excretion	Renal
Therapeutic considerations
Pregnancy cat.	A(AU) C(US)
Legal status	Pharmacist Only (S3)(AU) ?(CA) POM(UK) ℞-only(US)
Routes	Oral, inhalational, IV

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 Chronic obstructive pulmonary disease.

Salbutamol sulphate is usually given by the inhaled route for direct effect on bronchial smooth muscle. This is usually achieved through a metered dose inhaler (MDI), nebuliser or other proprietary delivery devices (e.g. Rotahaler or Autohaler). In these forms of delivery, the maximal effect of Salbutamol can take place within five to twenty minutes of dosing, though some relief is immediately seen. Salbutamol can also be given orally or intravenously. However, some asthmatics may not respond to these medications as they will not have the required DNA base sequence in a specific gene.

Salbutamol became available in the United Kingdom in 1969 and in the United States in 1980 under the trade name Ventolin.

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
• hyperkalaemia, especially in patients with renal failure
• can be aerosolized with a nebulizer for patients with cystic fibrosis, along with ipratropium bromide and pulmozyme.

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 Whilst preferred over agents such as atosiban and ritodrine, its role has largely been replaced by the calcium-channel blocker nifedipine which is more effective, better tolerated and orally administered.^[1]

Diet and Bodybuilding use

Salbutamol is taken by some as an alternative to Clenbuterol for purposes of fat burning.^[2]

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 airway, 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 five to fifteen minutes of administration.

In tocolysis, the activation of β₂-receptors results in relaxation of uterine smooth muscle, thus delaying labour.

Adverse effects

While 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, tinnitus, hyperactivity in children, and insomnia.^[1]

The (S) enantiomer of salbutamol can inhibit the anti-inflammatory effect of steroids prescribed to treat asthma. However, the (R) enantiomer can stimulate the steroid's effect and the overall effect of the two isomers is unclear.^[3]

skeletal formula of R-salbutamol

skeletal formula of S-salbutamol

ball-and-stick model of R-salbutamol

ball-and-stick model of S-salbutamol

Other brand names

Salbutamol is sold under the brand names Aerolin, Airomir, Asthalin, Asthavent, Asmol, Buventol, ProAir, Proventil, Salamol, Sultanol, Ventolin, and Volmax.

Levalbuterol, the R-enantiomer of salbutamol, is sold as Xopenex.

Ban of CFC-Containing Albuterol Inhalers

U.S. regulators have announced that albuterol inhalers containing chlorofluorocarbons (CFCs) will be banned in the United States beginning in 2009. This type of asthma inhaler had previously been given "essential use" status, exempting it from a national CFC-production ban. However, GlaxoSmithKline, Ivax Corp., and other manufacturers are expected to produce adequate supplies of alternative inhalers by 2009 and will offer discounts for those who cannot afford the newer versions, which cost about $20 more.

Curiously, in the United Kingdom, Australia and New Zealand, inhalers have been CFC free for some years now, which could bring into question the pricing issue.

References

1. Anabolic effects of the beta 2-adrenoceptor agonist salmeterol are dependent on route of administration N. G. Moore, G. G. Pegg, and M. N. Sillence Am J Physiol Endocrinol Metab, Sep 1994; 267: E475 - E484.
2. Schiffelers SL, Saris WH, Boomsma F, and van Baak MA. beta(1)- and beta(2)-Adrenoceptor-mediated thermogenesis and lipid utilization in obese and lean men. J Clin Endocrinol Metab 86: 2191-2199, 2001
3. Effect of salbutamol on muscle strength and endurance performance in nonasthmatic men. Med Sci Sports Exerc. 2000 Jul;32(7):1300-6. J Strength Cond Res. 2005 Feb;19(1):102-7. Oral Albuterol dosing during the latter stages of a resistance exercise program
4. The effects of Albuterol and isokinetic exercise on the quadriceps muscle group.Med Sci Sports Exerc. 1995 Nov;27(11):1471-6
5. Salbutamol, a beta 2-adrenoceptor agonist, increases skeletal muscle strength in young men.Martineau L, Horan MA, Rothwell NJ, Little RA
6. Different Ability of Clenbuterol and Salbutamol to Block Sodium Channels Predicts Their Therapeutic Use in Muscle Excitability Disorders Jean-François Desaphy, Sabata Pierno, Annamaria De Luca, Paola Didonna, and Diana Conte Camerino Mol. Pharmacol., Mar 2003; 63: 659
7. Metabolism. 1996 Jun;45(6):712-7 Effects of oral albuterol on serum lipids and carbohydrate metabolism in healthy men. Maki KC, Skorodin MS, Jessen JH, Laghi F

External links

• Volmax Drug Information (drugs.com)
• Albuterol

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