How do LTRAs work?
Inflammation of the airways is characterised by the presence of inflammatory white blood cells like mast cells and eosinophils which are involved in immune and inflammatory responses and produce chemicals that control these responses. Leukotrienes are one such inflammatory mediator and overproduction of leukotrienes is directly involved in causing symptoms of asthma in the airways and allergy in nasal passages. Leukotrienes are synthesised in response to several triggers, including an allergic reaction, physical stimulus like cold, which can in turn both trigger asthma. A leukotriene receptor antagonist (LTRA) like montelukast binds to specific leukotriene receptors on cells of the bronchioles and also other cells like macrophages that migrate to the airways, and this blocks the action of leukotrienes.
These LTRA medications are taken orally in tablet form to prevent leukotriene-mediated inflammation in asthma and allergic rhinitis and are slow-acting but long-lasting in their action.
LTRAs for asthma
When leukotrienes are released into the airways in response to an asthma trigger, they directly cause contraction of the smooth muscle of the bronchioles; also increased mucus production by secreting cells of the airways. These leukotriene-mediated effects cause bronchoconstriction or narrowing of the airways, inflammation, swelling and mucous secretion. LTRA medications are used to help manage chronic asthma and prevent exacerbations and asthma attack, but not to treat asthma attack. They are particularly useful for nocturnal and exercise-induced asthma because they are long-acting.
LTRAs for allergy
When leukotrienes are released into the nasal passages after exposure to an allergen like pollen or house dust mites they cause irritation and inflammation and this leads to symptoms of allergic rhinitis, including nasal congestion, runny itchy nose and sneezing.
LTRA medications are used to treat seasonal allergy to pollen, also known as hay fever, and perennial allergy, such as to animal fur, mould and house dust mites, to relieve symptoms of allergic rhinitis.