Beta2-Agonists

Excerpt

Beta-2 adrenergic agonists are a drug class used as a mainstay treatment for respiratory diseases such as bronchial asthma and chronic obstructive pulmonary disease (COPD). They replicate the functions of catecholamines such as epinephrine, norepinephrine, and dopamine in producing different autonomic responses within the body. Specifically, the smooth muscle of the airway, uterus, intestine, and systemic vasculature are areas where beta-2 agonists have the most significant effect. Thus, the focus of development for this drug class has been mainly on the clinical implications involving their ability to affect those target organ systems. Within the last century, there has been extensive research on the bronchodilatory and the anti-bronchoconstrictive properties of these drugs.

The early 1900s marked the advent of epinephrine as a form of treatment in Western medicine after successfully obtaining it from the adrenal gland; this became the treatment for asthmatic patients until its replacement in the 1940s with the formulation of isoproterenol, a non-selective beta-adrenoreceptor agonist. However, the adverse effects of isoproterenol became an issue of concern, and the search continued for a treatment with a better adverse effect profile. With the discovery of the alpha-1, alpha-2, beta-1, and beta-2 receptors in subsequent years, it became known that airway bronchodilation had a strong correlation specifically with beta-2 receptors in the lung vasculature. Pharmacological pursuits turned towards maximizing the selectivity towards the beta-2 receptor in an attempt to reduce the incidence of adverse effects of the non-selective isoproterenol. These new drugs, classified as beta-2 adrenergic receptor agonists, have since become frontline treatments for bronchial asthma and COPD. Subsequent research aims to improve efficacy, minimize adverse effects, decrease symptoms, reduce mortality rates, and improve patient quality of life. However, since the discovery of beta-2 agonists, there have been many discussions regarding the potential long-term risks versus benefits to the overall rate of morbidity and mortality. This article aims to provide a foundational background of the mechanism of action of beta-2 agonist, the various classifications, and their associated clinical significance, and discuss areas of concern and speculations regarding this class of medications.