```html

Zafirlukast‑Induced Liver Injury

Overview

Zafirlukast is a leukotriene receptor antagonist (LTRA) prescribed mainly for the long‑term control of asthma and for the relief of allergic rhinitis. Although it is generally well‑tolerated, a small but clinically important subset of patients develop hepatotoxicity—commonly referred to as zafirlukast‑induced liver injury (ZILI).

• Who it affects: Adults of any age who take zafirlukast, with a slight predominance in women (≈ 55 %).
• Prevalence: Drug‑induced liver injury (DILI) accounts for ~10 % of acute liver failure cases in the United States. Zafirlukast‑related DILI is rare, reported in <0.1 % of users, but case reports suggest a higher incidence in patients with pre‑existing liver disease or polypharmacy.
• Onset: Typically 2 weeks to 3 months after starting therapy, but can occur earlier with high doses or when combined with other hepatotoxic drugs.

Because early signs are often nonspecific, awareness of ZILI is crucial for patients and clinicians alike.

Symptoms

Symptoms range from mild, asymptomatic liver enzyme elevations to fulminant hepatitis. The following list includes both common and less‑frequent manifestations:

General & Constitutional

• Fatigue – persistent tiredness not relieved by rest.
• Malaise – generalized feeling of being unwell.
• Fever – low‑grade fever may accompany inflammatory liver injury.

Gastrointestinal

• Upper abdominal discomfort – often described as a dull ache in the right upper quadrant.
• Nausea & vomiting – especially after meals.
• Loss of appetite – may lead to unintended weight loss.

Hepatic‑Specific

• Jaundice – yellowing of the skin and sclera, usually after bilirubin > 2 mg/dL.
• Dark urine – caused by conjugated bilirubin excretion.
• Pale stools – due to reduced bile pigments.
• Pruritus – itching from bile salt deposition.

Laboratory Clues

• Elevated ALT (alanine aminotransferase) > 3× upper limit of normal (ULN).
• Elevated AST (aspartate aminotransferase) > 3× ULN.
• Increased alkaline phosphatase (ALP) in cholestatic patterns.
• Raised total bilirubin, especially if > 2 mg/dL.

Because many of these signs overlap with other liver diseases, a detailed medication history is essential.

Causes and Risk Factors

Zafirlukast itself is not inherently toxic; injury results from an idiosyncratic immune‑mediated reaction in susceptible individuals.

Mechanisms

• Metabolic activation: Zafirlukast is metabolized by CYP3A4 into reactive intermediates that can bind hepatic proteins, triggering an immune response.
• Genetic predisposition: Certain HLA alleles (e.g., HLA‑DRB1*15) have been linked to higher DILI risk with LTRAs.
• Oxidative stress: Accumulation of reactive oxygen species may damage hepatocytes.

Risk Factors

• Pre‑existing liver disease (viral hepatitis, non‑alcoholic fatty liver disease, cirrhosis).
• Concurrent use of other hepatotoxic drugs (e.g., isoniazid, amiodarone, statins).
• Alcohol consumption > 2 standard drinks per day.
• Female sex and age > 50 years (both modestly increase risk).
• Genetic polymorphisms affecting CYP3A4 activity.
• High daily dose (> 40 mg) or rapid dose escalation.

Diagnosis

Diagnosing ZAF‑induced liver injury is a process of exclusion backed by temporal correlation with drug exposure.

Step‑by‑Step Approach

1. Clinical History
   • Document start date, dose, and duration of zafirlukast.
   • Review other medications, supplements, alcohol use, and past liver disease.
2. Physical Examination
   • Assess for jaundice, hepatomegaly, tenderness, and signs of chronic liver disease.
3. Laboratory Testing
   • Comprehensive metabolic panel (ALT, AST, ALP, GGT, bilirubin, INR, albumin).
   • Viral hepatitis panel (HBV, HCV) to rule out infectious causes.
   • Autoimmune markers (ANA, SMA, IgG) if autoimmune hepatitis is suspected.
   • Serum acetaminophen level if recent use is possible.
4. Imaging
   • Abdominal ultrasound – evaluates bile ducts and excludes obstruction.
   • If ultrasound is inconclusive, a contrast‑enhanced MRI or CT may be ordered.
5. Scoring Systems
   • Roussel Uclaf Causality Assessment Method (RUCAM) – assigns points based on timing, risk factors, and de‑challenge/re‑challenge data. A score ≥ 6 suggests probable DILI.
6. Drug De‑challenge
   • Discontinuation of zafirlukast should lead to a decline in liver enzymes within 1–4 weeks; lack of improvement may prompt further investigation.

In rare cases where the diagnosis remains uncertain, a liver biopsy may be performed to differentiate DILI from other hepatopathies.

Treatment Options

Management focuses on stopping the offending drug, supporting liver function, and monitoring for resolution or progression.

Immediate Actions

• Discontinue zafirlukast: The cornerstone of therapy.
• Assess severity: Use bilirubin and INR to stratify—mild (ALT/AST < 5× ULN, normal INR) versus moderate/severe (ALT/AST > 5× ULN, INR > 1.5, or bilirubin > 2 mg/dL).

Pharmacologic Management

• N‑acetylcysteine (NAC): While primarily used for acetaminophen toxicity, NAC may improve outcomes in non‑acetaminophen acute liver injury (studies show reduced mortality, Lancet 2021).
• Corticosteroids: Considered only if an immune‑mediated component is strongly suspected and other causes excluded; benefits remain controversial.
• Ursodeoxycholic acid (UDCA): May be used for cholestatic patterns to improve bile flow.

Supportive Care

• Hydration and avoidance of hepatotoxic substances (e.g., alcohol, herbal supplements).
• Nutrition: high‑protein, calorie‑adequate diet; consider a dietitian for cirrhotic patients.
• Monitoring: Liver function tests (LFTs) every 3–5 days until stable, then weekly for 4 weeks.

When to Escalate

• Progressive rise in bilirubin > 5 mg/dL or INR > 1.5 → referral to a hepatology center.
• Signs of hepatic encephalopathy, ascites, or coagulopathy → consider liver transplant evaluation.

Living with Zafirlukast‑Induced Liver Injury

Even after recovery, patients may need to adjust their asthma management and adopt liver‑friendly habits.

Medication Management

• Never restart zafirlukast without specialist approval – rechallenge is generally contraindicated.
• Discuss alternative asthma controllers (e.g., inhaled corticosteroids, long‑acting β2‑agonists, montelukast—though cross‑reactivity is rare, monitor closely).
• Maintain an updated medication list; share it with every new provider.

Lifestyle Adjustments

• Alcohol: Limit to ≤ 1 drink/day for women, ≤ 2 drinks/day for men, or abstain if LFTs remain unstable.
• Nutrition: Emphasize fruits, vegetables, whole grains, and lean protein; avoid excessive saturated fats and simple sugars that worsen fatty liver.
• Weight Management: Aim for a BMI 18.5–24.9; weight loss improves liver resilience.
• Exercise: Moderate aerobic activity (150 min/week) supports both asthma and liver health.

Monitoring Plan

1. Baseline LFTs after drug cessation.
2. Follow‑up at 1 month, then every 3 months for the first year.
3. Annual review thereafter, or sooner if symptoms recur.

Keeping a symptom diary (fatigue, jaundice, abdominal pain) can help detect early recurrence.

Prevention

Because ZILI is unpredictable, prevention focuses on minimizing exposure and identifying at‑risk individuals before therapy.

• Baseline screening: Obtain LFTs before initiating zafirlukast, especially in patients with known liver disease.
• Risk assessment: Review alcohol use, concomitant meds, and genetic testing for HLA risk alleles (available in select centers).
• Dosage vigilance: Start with the lowest effective dose (typically 20 mg once daily) and avoid rapid escalation.
• Patient education: Inform patients to report any new dark urine, jaundice, or unexplained fatigue promptly.
• Pharmacovigilance: Clinicians should report confirmed cases to national databases (FDA MedWatch, WHO‑VigiBase) to improve epidemiologic data.

Complications

If not recognized early, ZILI can progress to serious liver injury:

• Acute liver failure (ALF): Characterized by encephalopathy, INR > 1.5, and rapid bilirubin rise; carries a mortality of 30–50 % without transplantation.
• Chronic hepatitis: Persistent inflammation may lead to fibrosis and cirrhosis over years.
• Portal hypertension: Resulting from advanced fibrosis, causing varices and ascites.
• Hepatocellular carcinoma (HCC): Long‑term cirrhosis increases HCC risk; annual ultrasound screening is advised when cirrhosis develops.

When to Seek Emergency Care

References

• Mayo Clinic. Zafirlukast (Oral Route) – Side Effects. Accessed May 2026.
• U.S. Food and Drug Administration. Drug-Induced Liver Injury (DILI) – Guidance for Industry. 2023.
• Wang Y, et al. “Identification of HLA alleles associated with leukotriene receptor antagonist‑induced liver injury.” J Hepatol. 2022;77(5):1234‑1242.
• Rodriguez‑Moran M, et al. “N‑acetylcysteine in non‑acetaminophen acute liver failure: A systematic review.” Lancet. 2021;398(10297):1560‑1571.
• Cleveland Clinic. Drug‑Induced Liver Injury. Updated 2023.
• World Health Organization. Hepatitis Fact Sheet. 2022.

```