Beta2-adrenergic
agonists
Beta2-adrenergic agonists are used to treat symptoms associatedwith
asthma and chronic obstructive pulmonary disease (COPD). Drugs in this class
can be either short-acting or long-acting.
Short-acting beta2-adrenergic agonists include:
·
albuterol (systemic, inhalation)
·
levalbuterol (inhalation)
·
metaproterenol (inhalation)
·
pirbuterol (inhalation)
·
terbutaline (systemic).
Long-acting beta2-adrenergic agonists include:
·
formoterol (inhalation)
·
salmeterol (inhalation).
Beta2-adrenergic
agonists are minimally absorbed from the GI tract; inhaled forms exert their
effects locally. After inhalation, beta2-adrenergic agonists appear to be absorbed over several hours from the
respiratory tract. These drugs don’t cross the blood-brain barrier; they’re
extensively metabolized in the liver to inactive compounds and rapidly excreted
in urine and stool.
Beta2-adrenergic agonists increase levels of cyclic adenosine
monophosphate by stimulating the beta2-adrenergic receptors in the
smooth muscle, resulting in bronchodilation. These drugs may lose their
selectivity at higher doses, which can increase the risk of toxicity. Inhaled
forms are preferred because they act locally in the lungs, resulting in fewer
adverse reactions than systemically absorbed forms.
Short-acting inhaled beta2-adrenergic agonists are the drugs
of choice for fast relief of symptoms in the patient with asthma. They’re
generally used as needed for asthma (including exercise-induced asthma) and
COPD. A patient with COPD may use them around-the-clock on a specified
schedule. How-ever, excessive use of a short-acting beta2-adrenergic
agonist may indicate poor asthma control, requiring reassessment of the
patient’s therapeutic regimen.
Long-acting beta2-adrenergic agonists tend to be used with
anti-inflammatory agents, namely inhaled corticosteroids, to help con-trol
asthma. (See Problems with long-acting
beta2-adrenergic ag-onists.) They’re especially useful for the
patient with nocturnalasthmatic symptoms. These drugs must be administered on a
schedule. They aren’t used to relieve acute symptoms because their onset of
action isn’t fast enough. They also don’t affect the chronic inflammation
associated with asthma.
Interactions are uncommon when using the inhaled
forms. Beta-adrenergic blockers decrease the bronchodilating effects of beta2-adrenergic agonists. They should be used together
cautious-ly. (See Adverse reactions to
beta2-adrenergic agonists.)
Related Topics
Privacy Policy, Terms and Conditions, DMCA Policy and Compliant
Copyright © 2018-2023 BrainKart.com; All Rights Reserved. Developed by Therithal info, Chennai.