Version July 2025
Atopic asthma (prophylactic treatment): Oral:
Infants and Children 6 months to 3 years: Initial: 0.05 mg/kg once daily or in 2 divided doses for 5 days; Maintenance: 0.05 mg/kg/dose twice daily (maximum dose: 1 mg twice daily)
Children >3 years and Adolescents: Initial: 1 mg once daily or in 2 divided doses for 5 days; Maintenance: 1 mg twice daily
Dosage adjustment for concomitant therapy: Significant drug interactions exist, requiring dose/frequency adjustment or avoidance. Consult drug interactions database for more information.
There are no dosage adjustments provided in the manufacturer's labeling.
There are no dosage adjustments provided in the manufacturer's labeling.
The following adverse drug reactions and incidences are derived from product labeling unless otherwise specified. Reported adverse reactions are for children and adolescents, unless otherwise noted.
1% to 10%:
Dermatologic: Skin rash (4%)
Endocrine & metabolic: Weight gain (5%)
Gastrointestinal: Abdominal pain (1%), increased appetite (1%)
Infection: Influenza (3%)
Nervous system: Sleep disturbance (1%)
Ophthalmic: Eyelid edema (1%)
Respiratory: Epistaxis (1%), respiratory tract infection (4%)
Frequency not defined: Hepatic: Increased liver enzymes
Postmarketing (any age):
Dermatologic: Erythema multiforme, Stevens-Johnson syndrome
Gastrointestinal: Nausea (Maclay 1984), xerostomia (Maclay 1984)
Genitourinary: Cystitis
Hypersensitivity: Hypersensitivity reaction
Nervous system: Central nervous system stimulation (including excitement, insomnia, irritability, nervousness), dizziness (Maclay 1984), drowsiness (Maclay 1984), headache (Maclay 1984), sedated state (Maclay 1984), seizure
Hypersensitivity to ketotifen or any component of the formulation; use of ketotifen syrup in patients sensitive to benzoate compounds
Concerns related to adverse effects:
• Hypersensitivity: Hypersensitivity reactions have occurred.
• Sedation: May cause drowsiness early in therapy; initiate therapy at one-half the recommended daily dose and gradually increase over 5 days to maintenance dose; patients must be cautioned about performing tasks which require mental alertness. (eg, operating machinery or driving).
• Thrombocytopenia: Rare cases of thrombocytopenia have been reported in patients concurrently using oral ketotifen and oral antidiabetic agents; manufacturer labeling does not specify associated agents but recommends to monitor platelet counts in patients receiving concomitant therapy.
Disease related concerns:
• Epilepsy: Use with caution in epileptic patients; may lower seizure threshold. Seizures have been reported rarely during therapy.
Special populations:
• Diabetics: Due to the carbohydrate content of the syrup preparation, diabetic patients may need to use tablet.
Dosage form specific issues:
• Benzoate allergy: Syrup products may contain benzoate compounds.
Other warnings/precautions:
• Appropriate use: Indicated for prophylactic treatment; not effective for the prevention or treatment of acute bronchospasm. Therapy with agents used for prophylaxis or relief of asthma related symptoms (eg, corticosteroids, beta2-agonists, xanthine derivatives), should be maintained for at least 6 to 12 weeks and then gradually reduced as clinically indicated. An immediate increase in corticosteroid dosage may be necessary in patients with severe relapse of symptoms during corticosteroid dose reduction; assess adrenal and pituitary function prior to initiating corticosteroid dose reduction in patients who have received long term therapy Steroid-dependent patients with adrenocortical insufficiency can take up to one year to recover a normal stress related pituitary-adrenal response.
• Delayed clinical response: Therapeutic effects may not be clinically evident until several weeks after the initiation of therapy; maximum effectiveness usually requires duration of therapy ≥10 weeks. Therapy should be maintained for at least 2 to 3 months to determine effectiveness. If therapy requires discontinuation, gradually reduce over 2 to 4 weeks.
Not available in the US
May be product dependent
Excipient information presented when available (limited, particularly for generics); consult specific product labeling. [DSC] = Discontinued product
Syrup, Oral:
Zaditen: 0.2 mg/mL ([DSC]) [contains alcohol, usp, methyl hydroxybenzoate, propyl hydroxybenzoate]
Tablet, Oral:
Zaditen: 1 mg
Oral: Administer without regards to meals.
Syrup: Use the measuring device that comes with this drug or a calibrated measuring device.
Note: Not approved in the United States.
Atopic asthma: Adjunctive therapy in the chronic treatment of mild, atopic asthma in pediatric patients ([syrup], ≥5 years of age [tablets]).
Limitations of use: Not indicated for relief of acute bronchospasm.
Ketotifen may be confused with ketoprofen
Zaditen may be confused with Zaditor
None known.
Note: Interacting drugs may not be individually listed below if they are part of a group interaction (eg, individual drugs within “CYP3A4 Inducers [Strong]” are NOT listed). For a complete list of drug interactions by individual drug name and detailed management recommendations, use the drug interactions program by clicking on the “Launch drug interactions program” link above.
Amezinium: Antihistamines may increase stimulatory effects of Amezinium. Risk C: Monitor
Benzylpenicilloyl Polylysine: Coadministration of Antihistamines and Benzylpenicilloyl Polylysine may alter diagnostic results. Management: Suspend systemic H1 antagonists for benzylpenicilloyl-polylysine skin testing and delay testing until systemic antihistaminic effects have dissipated. A histamine skin test may be used to assess persistent antihistaminic effects. Risk D: Consider Therapy Modification
Betahistine: Antihistamines may decrease therapeutic effects of Betahistine. Betahistine may decrease therapeutic effects of Antihistamines. Risk C: Monitor
Certoparin: Antihistamines may increase therapeutic effects of Certoparin. Risk C: Monitor
CNS Depressants: Ketotifen (Systemic) may increase CNS depressant effects of CNS Depressants. Risk C: Monitor
Hyaluronidase: Antihistamines may decrease therapeutic effects of Hyaluronidase. Risk C: Monitor
Pitolisant: Antihistamines may decrease therapeutic effects of Pitolisant. Risk X: Avoid
Adverse events have been observed in some animal studies.
Breast-feeding is not recommended by the manufacturer.
Syrup contains carbohydrate 4 g/5 mL.
Manufacturer labeling recommends monitoring of platelet counts in patients receiving oral antidiabetic agents.
Exhibits noncompetitive H1-receptor antagonist and mast cell stabilizer properties. Efficacy in asthma likely results from a combination of anti-inflammatory and antihistaminergic actions including interference with chemokine-induced migration of eosinophils into inflamed airways, inhibition of airway hyper-reactivity due to platelet activating factor (PAF), antagonism of leukotriene-induced bronchoconstriction.
Absorption: Rapid, almost complete.
Protein binding: ~75%.
Metabolism: Hepatic via N-glucuronidation to inactive metabolite ketotifen-N-glucoronide; N-demethylation to active metabolite nor-ketotifen; and keto-reduction to hydroxyl derivative.
Clearance: Increased in children >3 years; decreased in children ≤3 years.
Bioavailability: ~50%.
Half-life elimination: Biphasic: Distribution: 3 to 5 hours; Elimination: 21 hours.
Time to peak, plasma: 2 to 4 hours.
Excretion: Urine (>60% as metabolites, 1% as unchanged drug).
