zafirlukast
Meaning of zafirlukast: An asthma tablet that blocks the receptor for leukotrienes, chemicals released during an allergic reaction that tighten the airways.
Definition of zafirlukast
Zafirlukast is a prescription tablet taken to prevent asthma symptoms. It blocks the receptor for leukotrienes, inflammatory chemicals released by immune cells that tighten airway muscle, swell the lining and increase mucus. Blocking the receptor keeps those effects from occurring. It is a preventive treatment taken regularly rather than a rescue medicine, and it does not open airways that are already narrowed.
What are leukotrienes?
They are signaling chemicals built from a fatty acid stored in cell membranes. Mast cells and other immune cells release them when triggered by an allergen, exercise or aspirin in a susceptible person. Once released, leukotrienes act on receptors in the airway wall and produce three effects at once: the surrounding muscle contracts, the lining swells, and mucus glands step up production. The airway narrows from all three directions. Zafirlukast occupies the receptor so the leukotriene cannot bind, which prevents this inflammation from taking hold.
How does it compare with other asthma medicines?
| Medicine group | Role | Speed |
|---|---|---|
| Inhaled corticosteroid | Main preventer, broad anti-inflammatory | Days to weeks |
| Leukotriene receptor blocker | Oral preventer, one pathway only | Days |
| Short-acting bronchodilator | Rescue, relaxes airway muscle | Minutes |
Because it targets a single pathway, its effect is generally more modest than an inhaled steroid. Being a tablet, it also reaches the nose, which is why it can help allergic rhinitis occurring alongside asthma.
What else is worth knowing about it?
It is a receptor blocker, so it competes with the natural chemical rather than removing it. Food reduces how much is absorbed. The drug is handled by liver enzymes and can slow the breakdown of warfarin, raising its blood-thinning effect, so that combination is watched. Liver injury has been reported and is the reason for attention to symptoms such as marked tiredness, itching or yellowing of the skin. A separate drug, zileuton, blocks the enzyme that manufactures leukotrienes instead of blocking their receptor, arriving at a similar place by a different route.
Also known as
Used in a sentence
Zafirlukast was added as a controller alongside the inhaled corticosteroid.
Good to know
Zafirlukast is a preventer taken on a schedule and has no role in relieving an attack in progress, since it does not relax airway muscle that is already contracted.