Introduction
These are given in oral tablet form and are used to treat severe chronic asthma. They are only ever used in conjunction with corticosteroids.
Mechanism
- They block the LTD4 receptor on smooth muscle, which normally responds to leukotriene activation. Thus by blocking this receptor they prevent bronchoconstriction.
- Leukotrienes are generally released by eosinophils and mast cells, and cause bronchoconstriction, oedema, and excess mucous constriction (basically things to do with inflammation). By blocking their receptors we can reduce these effects
- They prevent both the early and late responses to an allergen.
- They are also particularly useful in asprin induced asthma as well as being used in excersize induced asthma, and other moderate cases.
- They are less effective than salbutamol and bronchodilation.
Drugs
- Montelukast – usually given once daily
- Zafirlukast – generally given twice daily
Unwanted effects
These are generally rare, but can include:
- Headache
- Irritability
- GI upset
- Dry mouth / thirst
- Oedema
- Hypersensitivity reactions
Clinical use
Generally used in conjunction with corticosteroids and β2 agonists, when the latter are no longer providing effective relief.