Flashcards
Beta2-Agonists
Cards in this deck (4)
- 1Give eg's of & indications for beta2-agonists.eg's: salbutamol & terbutaline (short acting). Salmeterol & formoterol (long acting). Long acting β2-agonists may be combined in an inhaler with a steroid, eg Symbicort or Seretide
Indications:
* Asthma - short-acting β2-agonists are used to relieve breathlessness. Long-acting β2-agonists are used as ‘step 3’ Rx for chronic asthma, but must always be given in combination with inhaled corticosteroids.
* COPD - short-acting β2-agonists are used to relieve breathlessness. Long-acting β2-agonists are an option for 2nd line therapy of COPD.
* Hyperkalaemia - nebulised salbutamol may be used as an additional Rx (alongside insulin, glucose & calcium gluconate) for the urgent Rx of a high serum potassium concentration. - 2MOA of B2-agonists.Beta2-receptors are found in smooth muscle of the bronchi. Stimulation of this G protein-coupled receptor activates a signalling cascade that leads to smooth muscle relaxation (Gs → ↑AC → ↑cAMP → ↓Ca2+ & ↑PKA = ↓MLCK).
β2-agonists also stimulate Na+/K+-ATPase pumps on cell surface membranes, thereby causing a shift of K+ from the extracellular to intracellular compartment. This makes them a useful adjunct in the Rx of hyperkalaemia.
Beta2-agonists are classified as short-acting (salbutamol, terbutaline) or long-acting (salmeterol, formoterol) according to their duration of effect. - 3SE's of beta2-agonists.• Tachycardia
• Palpitations
• Anxiety
• Tremor
• Muscle cramps (long-acting) - 4CI's, cautions, & important interactions of beta2-agonists.CI's:
• None
Cautions:
• Long-acting β2-agonists should be used in asthma only if an inhaled corticosteroid is also part of therapy.
• Cardiovascular disease
Important interactions:
Beta-blockers may reduce the effectiveness of β2-agonists. Concomitant use of high-dose nebulised β2-agonists with theophylline and corticosteroids can lead to hypokalaemia, so serum potassium concentrations should be monitored.