💊 Leukotriene Receptor Antagonists

Leukotriene Receptor Antagonists (LTRAs) are a class of medications used in the management of asthma and allergic rhinitis. They work by blocking the action of leukotrienes, inflammatory mediators.

LTRAs, such as montelukast, competitively and selectively inhibit the cysteinyl leukotriene 1 (CysLT1) receptor. This prevents the binding of leukotrienes (LTC4, LTD4, LTE4), which are potent pro-inflammatory mediators that cause bronchoconstriction, mucus secretion, and airway oedema in asthma.

LTRAs are primarily indicated as an add-on therapy for the maintenance treatment of mild to moderate asthma, particularly in patients who cannot tolerate inhaled corticosteroids or have predominant exercise-induced asthma. They are also used for the symptomatic relief of seasonal allergic rhinitis. They can be particularly useful in aspirin-sensitive asthma.

Absolute contraindications include hypersensitivity to the active substance or any excipients. There are generally few other absolute contraindications. Caution is advised in patients with severe hepatic impairment, although montelukast is primarily metabolised by the liver.

Common adverse effects are generally mild and include headache, abdominal pain, and upper respiratory tract infections. More serious but rare adverse effects include neuropsychiatric events such as agitation, aggression, depression, suicidal thoughts and behaviour, and sleep disturbances. Churg-Strauss syndrome has also been reported, though its causal link is debated.

Monitoring primarily involves assessing the patient's asthma control and symptom improvement. Patients and carers should be counselled to report any neuropsychiatric changes or unusual behaviour. No specific routine blood tests are usually required, but liver function tests might be considered in patients with pre-existing hepatic impairment.

Always check for allergies. Counsel patients, especially parents of children, about the potential for neuropsychiatric side effects and to report any changes in mood or behaviour. Emphasise that LTRAs are for maintenance, not for acute asthma attacks, and that they should continue their usual asthma medication.

Montelukast is the most common LTRA. Useful for aspirin-sensitive asthma and exercise-induced asthma. Not for acute attacks. Important to counsel on potential neuropsychiatric side effects. Often used in children who struggle with inhalers.

SBA questions often focus on LTRAs as an alternative or add-on therapy in asthma, especially for exercise-induced or aspirin-sensitive asthma. Traps might involve asking about their role in acute asthma attacks (they are not for acute relief) or their rare but serious neuropsychiatric side effects. Their use in children is also a common theme.