SOME COMMONLY PRESCRIBED BETA-2 AGONISTS

Albuterol (Ventolin; Proventil)

Salmeterol (Serevent)

Metaproterenol (Alupent)

Terbutaline (Brethine)

Pirbuterol (Maxair)

What is the difference in these drugs?

They all differ in their duration of action. A drug like Terbutaline is used many times a day, whereas Pirbuterol of Salmeterol last longer.

If these drugs are used chronically, over time they cause desensitization of the beta-2 receptors in the bronchial tree resulting in diminished bronchodilation effectiveness. So the physician will then take the patient off the drug class (called a “drug holiday”) and put them on another class of drugs for bronchodilation to let the beta-2 receptor regain its sensitivity. So we can say that the beta-2 receptors can build up a tolerance to the beta-2 agonists, whenever you expose any receptor to its agonists this can occur by down-regulation (Type II diabetes is another example of tolerance, in which there is an excess of insulin but the receptors are tolerant and so the effects of insulin do not occur).

Category: Pharmacology Notes