Zafirlukast
ICI-204219
Also known as: Accolate · Accoleit · Aeronix · Azimax · Olmoran · Resma · Vanticon · Zafarismal · Zafirst · Zuvair · ICI-204219
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Adjunctive treatment of atopic dermatitis | 20 mg (total dose) PO twice daily | PO | q12h | — | 🌎 NA |
| Adjunctive treatment of atopic dermatitis | 5 mg PO q12h, if the dog weighed less than 11.4 kg (25 lb); 10 mg PO q12h, if 11.4-22.3 kg (25-49 lb); 20 mg PO q12h, if 22.7-34.1 kg (50-75 lb); and 30 mg PO q12h, if greater than 34.1 kg (75 lb). | PO | q12h | — | 🌎 NA |
- Adjunctive treatment of atopic dermatitis: Only moderate success
- Adjunctive treatment of atopic dermatitis: Given on an empty stomach, 1 hour before, or 2 hours after meals.
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Adjunctive treatment of feline bronchial 'asthma' | 1-2 mg/kg PO once to twice daily | PO | q12-24h | — | 🌎 NA |
| Adjunctive treatment of feline bronchial 'asthma' | 0.5-1 mg/kg q12-24h. | PO | q12-24h | — | 🌎 NA |
| Adjunctive treatment of feline bronchial 'asthma' | 5 mg (total dose) per cat PO q12h. | PO | q12h | — | 🌎 NA |
| Adjunctive treatment of mild inflammatory bowel disease | 0.15-0.2 mg/kg PO once daily. | PO | q24h | — | 🌎 NA |
- Adjunctive treatment of mild inflammatory bowel disease: Author has used a combination of zafirlukast (3 months), famotidine (4 weeks), and sucralfate (2 weeks) (along with a low-allergen diet) to successfully treat a case.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Zafirlukast is an oral leukotriene-receptor antagonist used off-label in veterinary medicine. While theoretically promising for conditions driven by leukotriene-mediated inflammation—such as feline asthma, canine atopic dermatitis, and inflammatory bowel disease (IBD)—clinical efficacy in veterinary patients has been largely disappointing, limited, or not fully studied.
Clinical Pearl: Leukotrienes are potent inflammatory mediators produced via the lipoxygenase pathway. While blocking them is highly effective in human asthma, cats and dogs may rely on different primary inflammatory pathways (such as histamine, interleukins, or prostaglandins), which likely explains the variable and often poor clinical response to zafirlukast in these species.
Mechanism of action
Zafirlukast selectively and competitively inhibits leukotriene receptors, specifically targeting the LTD4 and LTE4 receptors.
- Arachidonic acid → 5-lipoxygenase pathway → Leukotrienes (LTC4, LTD4, LTE4)
- By blocking these receptors, zafirlukast prevents the binding of slow-reacting substance of anaphylaxis (SRS-A).
- This inhibition reduces smooth muscle contraction (bronchoconstriction), vascular permeability, and inflammatory cell infiltration associated with allergic and asthmatic responses.
Safety & warnings
Contraindications
- Hypersensitivity to zafirlukast
- Acute bronchospasm or acute asthma attacks
Adverse effects
- Vomiting (dogs)
- Headache (humans)
Precautions
Zafirlukast is not indicated for, and is ineffective for treating bronchospasm associated with acute asthma attacks. Patients with significantly decreased hepatic function may have reduced clearances (and increased plasma levels) of zafirlukast.
Drug interactions
May significantly increase zafirlukast plasma levels
May decrease the bioavailability of zafirlukast
May decrease plasma levels of zafirlukast
Zafirlukast may significantly increase the prothrombin time of patients taking warfarin
Monitoring
- Clinical efficacy
Pharmacokinetics
Absorption
Rapidly absorbed after oral administration (human data). Food may impair the absorption of the drug; therefore, give on an empty stomach. Peak plasma levels occur about 3 hours after dosing.
Distribution
Highly bound to plasma proteins (>99%).
Metabolism
Extensively metabolized.
Elimination
Less than 10% of a dose is excreted in the urine, the rest in the feces.
Overdose
In dogs, doses of up to 500 mg/kg were tolerated without mortality. Overdose is generally expected to be well tolerated, but supportive care should be provided if significant gastrointestinal signs occur.
Available products
Formulations
- Tablets (film-coated)
Human-labeled
- Zafirlukast Tablets (film-coated): 10 mg & 20 mg; Accolate® (AstraZeneca); (Rx)
Regulatory status
No regulatory data for: 🇺🇸 US · 🇪🇺 EU · 🇬🇧 UK · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Zafirlukast tablets should be stored at room temperature and protected from light and moisture. The manufacturer states that the tablets should be dispensed only in the original, unopened container.
Client information
- Administration: Preferably give on an empty stomach (1 hour before or 2 hours after meals) for optimal absorption.
- Not a Rescue Drug: Give this medication regularly even if your animal appears well. Do NOT use this medication to treat acute asthma attacks or sudden breathing difficulties.
- Monitoring: Because experience in veterinary medicine is limited, report any untoward effects (such as vomiting or lethargy) to your veterinarian immediately.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.