Asthma Medications - Specific Drugs: Old and New
The B-agonists were developed in the 1940s, with isoproterenol the first of the class. Like epinephrine (adrenaline) this agent has both beta-1 and beta-2 effects. Isoetharine was one of the first”selective”B2-adrenergic agonists introduced in the United States and it was followed by metaproterenol. With the development of selective B2-adrenergic agonists there is no place for the use of nonselective agents that have significant stimulatory effects on the heart and circulation. Further research has produced more potent and longer-acting selective agents.
For the Acute Asthmatic Attack: Short-Acting Agent
Several selective B2-adrenergic agonists are available for use. These agents are available as aerosol sprays delivered by metered-dose inhalers (MDIs), aerosol solution to be delivered by nebulization, dry powders for inhalation (DPI), short and long-acting tablets, and as syrups flavored for children. In the acute asthmatic attack the treatment of choice for prompt relief of symptoms is the administration of a short-acting B2-adrenergic agonist. B2-adrenergic agonists (albuterol, metaproterenol, pirbuterol, terbutaline, fenoterol, and bitolterol) have a rapid onset of action (within minutes) with a duration of action of four to six hours. The recommended dosage is two puffs every six hours as needed. These medications differ in potency as well as how fast they begin to work and when their peak effect is reached. There are also differences in how long the effect of the drug lasts. Fenoterol has never been made available in the United States. Its extremely rapid onset of action may have contributed to its overuse and it has been implicated in cases of fatal asthma in New Zealand. Table 1 lists the B2-agonists by generic and brand name as well as the types of preparations that are available.
