𝛃2 adrenoceptor agonists

𝛃2 adrenoceptor agonist...

1. EXAMPLES: Short-acting – salbutamol, terbutaline; long-acting – salmeterol, formoterol.
2. MECHANISM OF ACTION: Selective 𝛃2 adrenoceptor agonists in smooth muscle of upper airways that increase intracellular cAMP. This leads to smooth muscle relaxation and bronchodilation.

• Acute asthma (short-acting).
• Chronic asthma/COPD (long-acting).
• Premature labour.

• Hypersensitivity.

• Fine tremor.
• Hypokalaemia (if high doses given).
• Tachycardia.
• Headache.

• The effects of long-acting drugs last 12 h.
• Proportion reaching GI tract is metabolised by the liver. t½ varies; salbutamol 3–7 h and terbutaline 16–20 h.

• Monitor potassium levels if high doses of salbutamol given (especially in acute asthma).

• Should not be given with non-selective 𝛃2 blockers, due to opposing actions.
• In management of acute asthma, hypokalaemia may be potentiated by hypoxia and the use of theophylline, steroids and diuretics.

• Salbutamol can be administered by inhaler, nebuliser or IV in the management of acute asthma.
• Salbutamol can be used in the immediate management of hyperkalemia (increases uptake of potassium into cells).
• BTS guidelines recommend a stepwise approach to the management of chronic asthma. First-line therapy involves the use of short-acting 𝛃2 agonists; if symptoms are uncontrolled this is supplemented with inhaled corticosteroids and then long-acting 𝛃2 agonists.
• 𝛃2 agonists salbutamol and terbutaline can be used to delay uncomplicated premature labour (24–33 weeks gestation) by at least 48 h, by inhibition of uterine contractions.

This note has been edited and reviewed by the pharmacy doctors on NPS team.

• Published on December 17, 2021
• This note last updated in October 30, 2024