Beta2-adrenergic receptor agonist

Beta₂-adrenergic receptor agonists are a class of drugs used to treat asthma and other pulmonary disease states.

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Uses

They act on the β₂-adrenergic receptor, thereby causing smooth muscle relaxation resulting in dilation of bronchial passages, vasodilation in muscle and liver, relaxation of uterine muscle and release of insulin. Side effects such as insomnia, anxiety, and tremor occur in some patients. All β₂ agonists are available in inhaler form (either metered-dose inhalers, which aerosolize the drug, or dry powder which can be inhaled).

Salbutamol (known as albuterol in the U.S.) also comes in a solution form for nebulization, which is more commonly used in emergency rooms than inhalers. Salbutamol and terbutaline are also both available in oral forms.

In addition, several of these medications are available in intravenous forms including both salbutamol and terbutaline. It can be used in this form in severe cases of asthma, but more commonly it is used to suppress premature labor because it also relaxes uterine muscle, thereby inhibiting contractions.

Risks

On November 18, 2005, Food and Drug Administration (FDA) alerted health care professionals and patients that several long-acting bronchodilator medicines have been associated with possible increased risk of worsening wheezing (bronchospasm) in some people, and requested that manufacturers update warnings in their existing product labeling.

On June 29, 2006, Cornell University and Stanford University researchers reported that a meta-analysis they conducted found that "regularly inhaled beta-agonists (Orciprenaline/metaproterenol [Alupent], formoterol [Foradil], Fluticasone/salmeterol [Serevent, Advair] and Salbutamol/albuterol [Proventil, Ventolin, Volmax and others]) increased the risk of respiratory death more than twofold, compared with a placebo," while used to treat chronic obstructive pulmonary disease (COPD).^[1]

Types

They can be divided into two groups:

(1) short-acting and (2) long-acting.

Short-Acting Beta₂ Agonists

• salbutamol (albuterol)
• levalbuterol
• terbutaline
• pirbuterol
• procaterol
• metaproterenol
• fenoterol
• bitolterol mesylate

Long-Acting Beta₂ Agonists

• salmeterol
• formoterol
• bambuterol
• clenbuterol

References

1. ^ Ramanujan K. Common beta-agonist inhalers more than double death rate in COPD patients, Cornell and Stanford scientists assert. Chronicle Online. June 29, 2006. Available at: http://www.news.cornell.edu/stories/June06/Salpeter.COPD.kr.html. Accessed June 30, 2006.