Leukotriene Modifiers

Asthma isn’t just bronchospasm; it is inflammation. When mast cells and other immune cells are triggered, they release leukotrienes — inflammatory mediators built from arachidonic acid by the enzyme 5-lipoxygenase. Leukotrienes are potent: they cause bronchoconstriction, airway swelling (edema), and mucus — and they drive the sustained, allergic component of asthma that bronchodilators alone don’t touch.

This is a separate pathway from the β2-agonists (which relax muscle) and even from steroids (which broadly suppress inflammation). Leukotriene modifiers specifically switch off the leukotriene arm — useful as an add-on controller and especially in exercise-induced and allergy-driven asthma.

The class works at two points. Montelukast and zafirlukast are leukotriene-receptor antagonists — they block the CysLT1 receptor so leukotrienes can’t deliver their message. Zileuton works upstream: it inhibits 5-lipoxygenase, so the leukotrienes are never made. Either way the leukotriene effect is silenced.

The single most important teaching point: these are controllers, not rescuers. They are taken daily to prevent symptoms and have no role in an acute attack — montelukast’s slow, oral onset can’t open a closing airway. A patient must keep their rescue inhaler for that.

Leukotriene modifiers are generally well tolerated, which made a later safety signal notable: neuropsychiatric events — agitation, depression, sleep disturbance, and, rarely, suicidal thoughts/behavior. In 2020 the FDA added a boxed warning to montelukast after continued reports (including completed suicides), and now advises reserving it for allergic rhinitis only when other options fail. Zafirlukast and zileuton have carried similar warnings since 2009.

Separately, zileuton and zafirlukast can be hepatotoxic, so liver enzymes are monitored with those agents. But the headline nursing point is to counsel patients and families to watch for and report mood or behavior changes.