Ketotifen is a second-generation antihistamine and mast cell stabilizer indicated for the prophylactic management of chronic allergic conditions, including asthma, allergic rhinitis, conjunctivitis, and atopic dermatitis. It functions through a dual mechanism of action, inhibiting both the release of inflammatory mediators from mast cells and antagonizing histamine H1-receptors. This results in a comprehensive suppression of the allergic response, reducing both immediate and late-phase reactions. Its efficacy, favorable safety profile, and availability in multiple formulations make it a versatile option in long-term allergy control strategies.

Features

• Pharmacological class: H1-antihistamine and mast cell stabilizer
• Available formulations: Oral tablets (1 mg), oral solution/syrup, ophthalmic solution (0.025%)
• Onset of action: Systemic effects typically observed within several hours; maximal prophylactic benefit may take several days to weeks
• Half-life: Approximately 21 hours, supporting once or twice-daily dosing
• Excretion: Primarily renal
• Prescription status: Available by prescription in most jurisdictions; specific regulations may vary

Benefits

• Provides prophylactic protection against allergic triggers by stabilizing mast cells and preventing degranulation
• Reduces the frequency and severity of allergic asthma attacks and bronchospasm
• Alleviates symptoms of allergic conjunctivitis, including itching, redness, and tearing
• Minimizes nasal symptoms in allergic rhinitis such as sneezing, rhinorrhea, and congestion
• Offers long-term management with a low potential for sedation compared to first-generation antihistamines
• Suitable for pediatric and adult populations, with formulations tailored for different age groups

Common use

Ketotifen is primarily used for the prevention and treatment of chronic allergic disorders. It is indicated for prophylactic management of bronchial asthma, particularly in cases where allergens are identifiable triggers. It is also prescribed for allergic rhinitis, providing relief from seasonal or perennial symptoms. The ophthalmic formulation is used specifically for allergic conjunctivitis, reducing ocular itching and inflammation. Off-label uses may include management of certain urticarias, mast cell activation syndromes, and adjunctive treatment in some eosinophilic disorders, though these applications should be guided by specialist assessment.

Dosage and direction

Adults and adolescents (12 years and older):
The typical oral dosage is 1 mg twice daily, taken with water. Dosage may be adjusted based on clinical response and tolerability, though should not exceed 2 mg twice daily.

Children (3–11 years):
A weight-based dosage is often used: 0.5 mg to 1 mg twice daily. Oral solution formulations allow for precise dosing in pediatric patients.

Ophthalmic solution:
Instill one drop into the affected eye(s) twice daily, approximately 8–12 hours apart.

Administration with food may minimize potential gastrointestinal discomfort. Consistent use is necessary for optimal prophylactic effect. Dosage adjustments are recommended in patients with renal impairment.

Precautions

Patients should be monitored for drowsiness, especially during the initial treatment phase or after dose increases. Caution is advised when operating machinery or driving until individual response is determined. Use with care in patients with a history of seizures, as ketotifen may lower the seizure threshold. Renal function should be assessed before and during prolonged therapy. Elderly patients may be more susceptible to adverse effects such as sedation or dizziness. Pregnancy and lactation require careful risk-benefit evaluation under medical supervision.

Contraindications

Hypersensitivity to ketotifen or any component of the formulation. Use is contraindicated in patients with acute asthmatic attacks or status asthmaticus, as ketotifen is not a rescue medication. Avoid in individuals with severe renal impairment without dosage adjustment and monitoring. Not recommended during the first trimester of pregnancy unless clearly necessary.

Possible side effect

Common side effects include drowsiness, dry mouth, dizziness, and weight gain. Less frequently, nausea, irritability, and nasal dryness may occur. Ophthalmic formulations may cause transient burning, stinging, or conjunctival hyperemia. Rare but serious adverse effects include thrombocytopenia, hepatitis, and seizures. Most side effects are dose-dependent and may diminish with continued use.

Drug interaction

Ketotifen may potentiate the sedative effects of alcohol, benzodiazepines, opioids, and other CNS depressants. Concurrent use with monoamine oxidase inhibitors (MAOIs) is not recommended due to theoretical risks of enhanced anticholinergic and sedative effects. Ketotifen may interact with other antihistamines or mast cell stabilers, though often used synergistically under medical supervision. Caution is advised with drugs that prolong QT interval.

Missed dose

If a dose is missed, it should be taken as soon as remembered unless it is nearly time for the next scheduled dose. In that case, skip the missed dose and resume the regular dosing schedule. Do not double the dose to make up for a missed one.

Overdose

Symptoms of overdose may include severe drowsiness, confusion, tachycardia, hypotension, and respiratory depression. Gastric lavage and activated charcoal may be considered if ingestion was recent. Supportive care should include monitoring of vital signs and ECG. There is no specific antidote; treatment is symptomatic and supportive.

Storage

Store at room temperature (15–30°C), protected from light and moisture. Keep all formulations out of reach of children. Do not use oral or ophthalmic solutions beyond the expiration date or if discoloration or precipitation is observed.

Disclaimer

This information is intended for educational purposes and does not replace professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before starting or changing any medication regimen. Individual patient needs and responses may vary.

Reviews

Clinical studies and meta-analyses support the efficacy of ketotifen in reducing asthma exacerbations and improving symptom control in allergic conditions. It is generally well-tolerated, with a safety profile favorable for long-term use. Patient-reported outcomes often indicate improved quality of life and reduced reliance on rescue medications. Specialist consensus acknowledges its role in stepwise allergy management, particularly where avoidance and first-line treatments are insufficient.