Zukast20 mg

Zukast is a leukotriene receptor antagonist (LTRA) indicated for the prophylaxis and chronic maintenance treatment of asthma in adults and children.

Established / FDA-approved use

• Prophylaxis and long-term maintenance treatment of chronic asthma in adults and children 5 years of age and older.

Important limitation of use

Zukast is not indicated for reversal of acute bronchospasm, including status asthmaticus. It is not a rescue medication; patients must have a separate fast-acting bronchodilator available at all times for acute asthma symptoms.

Each film-coated tablet of Zafirlukast is formulated with zafirlukast as the active pharmaceutical ingredient, commonly available in strengths of 10 mg and 20 mg, along with standard pharmaceutical excipients such as microcrystalline cellulose, lactose, croscarmellose sodium, povidone, and magnesium stearate.

Zukast is an orally active, selective leukotriene receptor antagonist belonging to the class of anti-asthmatic agents. It works by blocking the action of cysteinyl leukotrienes, inflammatory mediators involved in the pathophysiology of asthma, including airway edema, smooth muscle constriction, and altered cellular activity associated with the inflammatory process.

Zukast is used as a long-term controller medication and is taken regularly to prevent asthma symptoms; it does not provide immediate relief during an acute attack.

Leukotriene receptor antagonist (anti-asthmatic / anti-leukotriene agent); therapeutic class of Zukast.

Zafirlukast is a selective and competitive antagonist of the cysteinyl leukotriene receptor CysLT1, including leukotrienes LTC4, LTD4, and LTE4. These leukotrienes are released from mast cells and eosinophils and contribute to airway edema, smooth muscle contraction, and altered cellular activity associated with the asthmatic inflammatory process.

By blocking these receptors, Zafirlukast helps reduce bronchoconstriction and airway inflammation associated with chronic asthma, providing prophylactic benefit rather than acute bronchodilation.

Pharmacokinetics

• Absorption: Well absorbed orally; bioavailability is reduced by approximately 40% when taken with food, so administration on an empty stomach is recommended.
• Metabolism: Extensively metabolized in the liver, primarily via CYP2C9, with some involvement of CYP3A4.
• Elimination: Mostly excreted in feces via biliary elimination; a small fraction is excreted in urine.

• Take Zukast tablets by mouth, on an empty stomach — at least 1 hour before or 2 hours after a meal — for optimal absorption.
• Swallow the tablet whole; continue taking it regularly, even when asymptomatic, as part of long-term asthma control.
• Do not use Zukast to treat an acute asthma attack; keep a fast-acting rescue inhaler available at all times.
• Do not stop taking Zukast abruptly without consulting a physician, especially while tapering oral corticosteroids (see Precautions and Warnings).

Zukast is metabolized via CYP2C9 and also inhibits CYP2C9 and CYP3A4, which can lead to clinically significant interactions:

• Warfarin: Zukast can increase warfarin exposure and significantly prolong prothrombin time (INR); close INR monitoring and dose adjustment of warfarin are recommended when co-administered.
• Aspirin: Co-administration increases plasma levels of Zukast by approximately 45%; monitor for increased adverse effects.
• Erythromycin: Reduces plasma concentration and bioavailability of Zukast by approximately 40%, which may reduce efficacy.
• CYP2C9 substrates (e.g., phenytoin, carbamazepine, tolbutamide): Zukast may increase levels of these drugs through enzyme inhibition; clinical monitoring is advised.
• Food: Reduces bioavailability of Zukast by about 40%; administer apart from meals (see Administration).

Common side effects of Zukast include:

• Headache
• Nausea
• Diarrhea
• Pharyngitis and upper respiratory infection
• Generalized pain and accidental injury

Serious but rare risks — including hepatotoxicity, neuropsychiatric events, and Churg-Strauss syndrome — are discussed in detail under Precautions and Warnings; seek medical attention promptly if these occur.

Pregnancy: Zukast corresponds to (legacy) FDA Pregnancy Category B; animal reproduction studies have not shown evidence of fetal harm at high doses, but adequate and well-controlled studies in pregnant women are limited. Zukast should be used during pregnancy only if clearly needed and if the potential benefit justifies the potential risk to the fetus; consult a physician before use.

Lactation: It is not established whether Zukast is excreted in human breast milk. Because many drugs are excreted in breast milk and the effect on a nursing infant is unknown, caution is advised, and a physician should be consulted before use of Zukast while breastfeeding.

Hepatotoxicity

Rare but serious cases of liver injury, including hepatic failure (some fatal or requiring transplantation), have been reported with Zukast. Discontinue Zukast and evaluate liver function promptly if symptoms such as jaundice, right upper quadrant pain, nausea, fatigue, lethargy, pruritus, flu-like symptoms, or anorexia occur. Periodic liver function monitoring may be reasonable, particularly during the early months of treatment.

Neuropsychiatric events

Neuropsychiatric events, including agitation, aggression, anxiety, hallucinations, depression, insomnia, and suicidal thinking/behavior, have been reported with Zukast. Patients and caregivers should be counseled to report any new or worsening mood or behavioral changes, particularly in pediatric patients.

Churg-Strauss syndrome

A rare systemic eosinophilic vasculitis (Churg-Strauss syndrome) has been reported in association with Zukast use, sometimes occurring during reduction of oral corticosteroid therapy. Monitor for worsening pulmonary symptoms, eosinophilia, vasculitic rash, cardiac complications, or neuropathy in this context.

Not for acute asthma attacks

Zukast is not a bronchodilator and must not be used to treat acute asthma exacerbations or status asthmaticus. Patients must have a fast-acting rescue bronchodilator available at all times.

Food effect

Bioavailability of Zukast is reduced by food; take it at least 1 hour before or 2 hours after meals for optimal effect.

Limited clinical experience with overdose of Zukast is available, and no specific antidote exists. In case of suspected overdose, seek immediate medical attention or contact a poison control center. Management is supportive and symptomatic, and may include gastrointestinal decontamination (e.g., under medical supervision) along with monitoring of vital signs and liver function.

Store at room temperature (below 30°C), away from light and moisture. Keep out of reach of children.

Hepatic impairment

Zukast is contraindicated in patients with hepatic impairment, including cirrhosis (see Contraindications).

Renal impairment

No specific dose adjustment of Zukast is established for renal impairment; use with routine clinical monitoring.

Elderly

Clearance of Zukast may be reduced 2- to 3-fold in patients 65 years and older; the standard adult dose is used, with attentive clinical monitoring.

Pediatric use

See Pediatric Uses for age-specific dosing and safety information for Zukast.

Zukast is intended for long-term, chronic maintenance therapy of asthma and should be continued regularly, including during symptom-free intervals, unless a physician advises otherwise. The duration of treatment is individualized based on clinical response and is periodically reassessed by the treating physician; it is not intended for short-term or as-needed use.

Leukotriene receptor antagonists (LTRAs); anti-asthmatic / anti-allergic agents.

Zafirlukast selectively and competitively antagonizes the cysteinyl leukotriene receptor (CysLT1), blocking the effects of leukotrienes LTC4, LTD4, and LTE4. These leukotrienes are potent inflammatory mediators released from mast cells and eosinophils that cause bronchoconstriction, increased vascular permeability, mucus secretion, and eosinophil recruitment in asthmatic airways. By inhibiting these effects, Zafirlukast reduces airway inflammation and prevents bronchospasm associated with chronic asthma.

B

Zukast is approved for use in children 5 years of age and older for the prophylaxis and chronic treatment of asthma.

• Children 5–11 years: 10 mg orally twice daily.
• Children 12 years and older: same as adult dose, 20 mg orally twice daily.

Safety and efficacy of Zukast in children younger than 5 years have not been established. Neuropsychiatric events have been reported with Zukast, and caregivers of pediatric patients should be counseled to watch for behavioral changes and report them promptly to the prescribing physician.