Long acting β2 agonists in adult asthma
(Published 06 August 2013)
Cite this as: BMJ 2013;347:f4662
- Graeme P Currie, consultant chest physician1,
- Iain Small, general practitioner2,
- Graham Douglas, consultant physician1
- 1Respiratory Unit, Aberdeen Royal Infirmary, Aberdeen AB25 2ZN, UK
- 2Peterhead Health Centre, Peterhead AB42 2XA, UK
- Correspondence to: G P Currie
- Accepted 20 May 2013
A 30 year old man with asthma, previously well controlled with inhaled beclometasone 100 μg (two puffs twice daily) and salbutamol (as required), presented to his general practitioner with a three month history of increasing breathlessness and wheeze, primarily overnight and in the mornings. He was a non-smoker with no obvious trigger factors. He reported using his inhaler as prescribed, and his technique was satisfactory. He had no other medical history and no symptoms of allergic rhinitis. His general practitioner suggested a further inhaler containing a long acting β2 agonist (LABA), but the patient expressed concerns as he had read that these inhalers were linked to an increased risk of fatal asthma.
What are long acting β2 agonists?
LABAs have become an increasingly popular treatment over the past two decades as a supplement to inhaled corticosteroids in the management of persistent asthma.1 They have a bronchodilator effect when bronchomotor tone (the state of airway smooth muscle contraction or relaxation regulating airway calibre) is low, and a protective (or “airway stabilising”) effect with increased bronchomotor tone.2
Salmeterol and formoterol (the two LABAs in widespread clinical use) are lipophilic, bind to airway smooth muscle β2 adrenoceptors and exert effects for approximately 12 hours. Salmeterol has a slower onset of action (10-30 minutes) than formoterol (1-3 minutes). Both drugs can be prescribed in single inhaler devices, but they are commonly given with different inhaled corticosteroids with varying doses in combination inhaler devices (table 1⇓, fig 1⇓).