Cromones – e.g.Sodium cromoglicate, nedocromil sodium
This is often described as a mast cell stabilizer. It prevents the release of inflammatory mediators (such as histamine) from mast cells.
These drugs have no bronchidilator activity, and thus are of no use in an asthma attack; thus they are preventative. They are usually less effective than inhaled corticosteroids.
Their main use is in mild-to-moderate, antigen induced and exercise induced asthma. They are also used as an inhalant to treat seasonal rhinitis, and as an ophthalmic agent to treat conjunctivitis.
Mechanism
- It enhances phosphorylation of a specific protein in mast cells. this protein interferes with signal transduction pathways to cause a reduction in the release of inflammatory mediators by mast cells.
- It also affects sensory C-fibres, and this can help reduce bronchoconstriction as a result of direct irritation (e.,g. by sulphur dioxide)
- If used long-term, they reduce chemotaxis of, and thus accumulation of eosinophils, neutrophils and macrophages in the lung, thus reducing the effect of any late phase reaction
- They act on B cells, to reduce IgE production
Use
The very first dose will protect against the early phase reaction. Treatment may be required for 1-2 months to provide protection against the late phase reaction
- Only about 1/3 of people benefit from using these drugs‼which means they are far less effective than inhaled corticosteroids. However, they have very few unwanted effects, thus are often tried first before inhaled corticosteroids.
Pharmacokinetics
- Poorly absorbed across membranes – this means when given by inhalation, they stay at the site of action for a very long time – which is very handy!
- Usually given as a powdered dose to be inhaled
Unwanted effects
- Cough, wheeze and throat irritation can sometimes occur after use – this occurs transiently.