Ketotifen

Pronunciation: kee-TOH-tih-fen.

Generic name
ketotifen
Drug class
Second-generation H1-antihistamine and mast-cell stabiliser
Form
Ophthalmic solution 0.025% (Zaditor/Alaway/Zaditen eye drops); oral tablet 1 mg or syrup 1 mg/5 mL (Zaditen, outside the United States)
Route
Ophthalmic (eye drops) or oral (tablet/syrup, outside the United States)
Legal status
Over-the-counter (ophthalmic solution, United States); prescription or pharmacy-level in other markets depending on form and country

Availability and supply rules vary by country

Trade names by country: United States · United Kingdom · Canada · Australia · New Zealand

Australia: Zaditen (and pharmacy-own-brand generics: Chemists' Own, Blooms The Chemist, Zoptic, Pharmacy Health, Apohealth, Priceline Pharmacy) (7) · Full directory

What ketotifen is and how it works

Ketotifen is an antihistamine that also stabilises mast cells, reducing the release of histamine and other substances that cause allergic itching and inflammation. The eye-drop form is used for allergy-related eye itching and is available without a prescription in the United States. The oral tablet/syrup form, available in Canada, the UK, the EU, and (via restricted access) Australia, is used for allergic rhinitis and conjunctivitis and, in some countries, as an add-on for asthma prevention. (1) (5)

There is no boxed warning for either form of ketotifen in any of the 6 markets reviewed. The oral form can cause drowsiness and, rarely, seizures in people with epilepsy, so it needs a clinician's involvement before starting -- never begin, stop, or change an oral ketotifen regimen on your own.

Mechanism of action: how ketotifen works

Ketotifen is a benzocycloheptathiophene-derivative H1-receptor antagonist that also stabilises mast cells, reducing the release of histamine, leukotrienes, prostaglandins, and platelet-activating factor involved in immediate (type I) allergic reactions. (2) (5)

What ketotifen is used for

Allergic conjunctivitis (itchy eyes) -- ophthalmic solution

Temporarily relieves itchy eyes caused by common allergens such as pollen, ragweed, grass, and animal hair or dander. (1) (4)

Allergic rhinitis and conjunctivitis -- oral tablets/syrup (outside the United States)

Used outside the US to treat symptoms of allergic rhinitis (sneezing, runny/itchy nose) and conjunctivitis, and in some countries as an add-on treatment to help prevent asthma symptoms (not for treating an asthma attack already underway). (5) (3)

Before taking ketotifen

Do not take / not appropriate for

  • Do not use the eye-drop solution if it has changed colour or become cloudy, if you are sensitive to any ingredient, or to treat contact-lens-related eye irritation. (all countries, ophthalmic form) (1)
  • Do not take oral ketotifen if you have a known allergy to ketotifen. (all countries, oral form) (5)
  • In the United Kingdom, oral ketotifen tablets are contraindicated in pregnancy and breastfeeding per the licensed Patient Information Leaflet -- a stricter position than the general 'discuss with your doctor' caution used for the oral form in some other markets; always follow your own country's licensed advice. (United Kingdom, oral form) (5)
  • Oral tablets contain lactose and are not suitable for people with certain rare hereditary lactose-intolerance conditions. (United Kingdom, oral form) (5)

Tell your clinician about

  • Whether you have epilepsy or a history of seizures, before starting oral ketotifen.
  • Whether you have diabetes and take oral antidiabetic medicines, since a rare, reversible drop in platelet count has been reported with this combination and needs monitoring.
  • Whether you wear contact lenses, if using the eye-drop form.
  • Whether you are pregnant, planning pregnancy, or breastfeeding, for either form.
  • All other medicines you take, especially other antihistamines, anti-anxiety or sleep medicines, and diabetes medicines.
(5) (2)

How to take ketotifen

  • Eye drops: remove contact lenses before use and wait at least 10 minutes before reinserting them; avoid touching the dropper tip to your eye or any surface; replace the cap after each use.
  • Oral tablets/syrup: swallow with the dose your clinician has set for you; do not change your dose or ask the prescriber about stopping it without your clinician's guidance.
  • If using the eye drops together with another eye medicine, leave at least 5 minutes between the two.
  • Oral ketotifen may increase the effects of alcohol and other sedating medicines -- avoid alcohol and discuss any sedating medicines with your clinician while taking it.
(1) (5)

Procedures and treatment changes

Tell the treating team before surgery, procedures, or any medicine change. Do not alter treatment without the responsible clinician. (1) (2) (3) (4) (5) (6) (7) (8)

Missed dose

If you miss a dose of either form, take the next dose at its usual scheduled time. Do not use two doses at once to make up for a missed one. Contact your pharmacist or clinician if you are unsure what to do.

Overdose

Seek urgent medical attention if you or a child may have swallowed a large amount of oral ketotifen, or if you develop severe drowsiness, an irregular heartbeat, confusion, or loss of consciousness. For the eye-drop form, contact a doctor or poison control if it is accidentally swallowed. (2)

Side effects

Side effects and their urgency vary; report severe, persistent, or concerning symptoms.

Eye drops: mild eye redness, burning or stinging, or headache.

What to notice: Eye drops: mild eye redness, burning or stinging, or headache.

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (7)

Oral form: drowsiness, dry mouth, and dizziness, which usually settle within a few days.

What to notice: Oral form: drowsiness, dry mouth, and dizziness, which usually settle within a few days.

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (5)

Oral form: weight gain (more common) and nervousness (less common).

What to notice: Oral form: weight gain (more common) and nervousness (less common).

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (2)

Oral form: nosebleeds (rare).

What to notice: Oral form: nosebleeds (rare).

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (2)

Serious warnings

Seizures (convulsions), oral form only — high caution

Symptoms: Uncontrolled shaking or jerking movements, loss of awareness, or a known history of epilepsy worsening.

Action: Contact your clinician or seek emergency care immediately -- oral ketotifen may increase the risk of seizures in people with epilepsy, which is why a clinician needs to know your seizure history before you start. (5) (2)

Unusual bruising or bleeding, oral form combined with diabetes medicines — high caution

Symptoms: Unexplained bruising, small red or purple spots on the skin, or unusual bleeding.

Action: Contact your clinician promptly for a platelet-count check -- a rare, reversible drop in platelet count has been reported when oral ketotifen is combined with oral antidiabetic medicines. (2)

Severe skin reaction, oral form — emergency

Symptoms: Blistering or peeling skin, a widespread rash, or mouth/eye sores.

Action: Seek emergency medical help immediately. (5)

Eye symptoms that do not fit ordinary allergy itching, eye-drop form — moderate

Symptoms: Eye pain, changes in vision, eye redness, or itching that worsens or lasts more than 72 hours.

Action: seek medical advice promptly, and let the clinician you see advise on whether to continue or stop the eye drops -- these symptoms are outside what the eye-drop label describes as ordinary allergy itching and need assessment. (1)

Interactions

  • Oral ketotifen can increase the sedating effects of alcohol, sleep aids, and anti-anxiety medicines. (5)
  • Combining oral ketotifen with oral antidiabetic medicines has rarely been linked to a reversible drop in platelet count; your clinician may recommend periodic platelet checks if this combination is needed. (2)
  • Other antihistamines taken together with oral ketotifen may increase drowsiness. (5)
  • If using the eye-drop form with another eye medicine, separate doses by at least 5 minutes. (4) (8)

Pregnancy, breastfeeding, kidney/liver function, age

Pregnancy

For the oral form, the UK licensed Patient Information Leaflet lists pregnancy as a contraindication; other markets' oral labelling calls for a doctor's assessment. For the eye-drop form, discuss use with your doctor if pregnant, since ophthalmic-specific pregnancy data is limited across the sources reviewed. (1) (2) (3) (4) (5) (6) (7) (8)

Breastfeeding

For the oral form, the UK licensed Patient Information Leaflet lists breastfeeding as a contraindication; other sources note limited data and recommend an individual risk-benefit discussion with your clinician. Ketotifen passes into breast milk after oral dosing. (1) (2) (3) (4) (5) (6) (7) (8)

Children

Eye-drop form: not recommended for children under 3 years without a doctor's guidance; approved down to age 3 in the markets reviewed. Oral form: not recommended for children under 3 years; paediatric dosing for ages 3 and older, and specialist weight-based dosing from 6 months to 3 years, is described in some markets' product information but is not an FDA-approved regimen anywhere in the US. (1) (2) (3) (4) (5) (6) (7) (8)

Elderly

No specific dose adjustment based on age alone is described in the sources reviewed for either form, though drowsiness from the oral form may need extra caution in older adults. (1) (2) (3) (4) (5) (6) (7) (8)

Hepatic_impairment

Not specifically detailed for ketotifen in the sources reviewed for this dossier -- discuss with your clinician if you have significant liver disease. (1) (2) (3) (4) (5) (6) (7) (8)

Renal_impairment

Not specifically detailed for ketotifen in the sources reviewed for this dossier -- discuss with your clinician if you have significant kidney disease. (1) (2) (3) (4) (5) (6) (7) (8)

Monitoring

Before starting

  • Epilepsy/seizure history (oral form)
  • Current diabetes medicines (oral form, for the rare platelet interaction)
  • Contact lens use (eye-drop form)
  • Pregnancy/breastfeeding status

During treatment

  • Watch for drowsiness, dizziness, or reduced alertness with the oral form, especially when starting treatment or combined with alcohol.
  • Periodic platelet-count checks if oral ketotifen is combined with oral antidiabetic medicines.
  • Watch for eye pain, vision changes, or worsening redness beyond 72 hours with the eye-drop form.
(5) (1)

Storage

Store the eye-drop solution between 4-25 degC (39-77 degF), away from children, and use only in the eye. Store oral tablets/syrup at room temperature in their original packaging, away from children, following the specific storage instructions on your pack.

Study the drug class: Antihistamines

Professional information

Clinician-facing context only, sourced from the current US DailyMed OTC label (ophthalmic), UK emc SmPC/PIL, and Health Canada product monograph; verify against the current full label before prescribing or recommending.

United States, United Kingdom, European Union, Canada, Australia, New Zealand

Indication: Allergic conjunctivitis (ophthalmic solution)

Dose summary: 1 drop in the affected eye(s) twice daily, every 8-12 hours; children 3 years and older use the same regimen; not recommended under age 3 without medical guidance.

Renal context: Systemic exposure from ophthalmic dosing is minimal (approximately 1.5% of the oral daily dose per New Zealand data), so renal dose adjustment is not described in the sources reviewed. (1) (8)

United Kingdom, European Union, Canada (Special Access Scheme only in Australia; not available in the United States)

Indication: Allergic rhinitis/conjunctivitis and adjunct asthma prophylaxis (oral tablets/syrup)

Dose summary: Adults 1-2 mg twice daily; children 3 years and older 1 mg twice daily, titrated per local product information; not effective for treating an acute asthma attack already underway.

Renal context: Not specifically detailed in the sources reviewed for this dossier. (5) (3)

Mechanism of action

Hepatic guidance

Not specifically detailed for ketotifen in the sources reviewed for this dossier.

Overdose note

No specific antidote; manage with supportive care, monitoring for excessive sedation, and cardiac monitoring if indicated for oral overdose. (2) (5)

Frequently asked questions

Is ketotifen available as both eye drops and tablets everywhere?

No. The eye-drop form (Zaditor/Alaway/Zaditen eye drops) is available in all 6 markets reviewed, over-the-counter in the United States. The oral tablet/syrup form (Zaditen) is not an FDA-approved product in the United States at all; it is available in Canada, the UK, and the EU, and in Australia only through the restricted Special Access Scheme rather than as a standard registered product. (1) (7)

Does ketotifen have a boxed warning?

No. Neither the eye-drop form nor the oral tablet/syrup form carries a boxed warning in any of the 6 markets reviewed. The eye-drop form is regulated in the US as an over-the-counter Drug Facts label, a category that does not use boxed warnings. (1)

Can I take oral ketotifen if I have epilepsy?

Tell your clinician if you have epilepsy or a history of seizures before starting oral ketotifen -- it may increase seizure risk, and your clinician needs to weigh this before you start. (5) (2)

What is the mechanism of action of ketotifen?

Ketotifen is a benzocycloheptathiophene-derivative H1-receptor antagonist that also stabilises mast cells, reducing the release of histamine, leukotrienes, prostaglandins, and platelet-activating factor involved in immediate (type I) allergic reactions. (2) (5)

What is the generic name of Ketotifen?

The generic name is ketotifen. (1) (2)

What class of drug is ketotifen?

Ketotifen is classed as: Second-generation H1-antihistamine and mast-cell stabiliser. (1) (2)

References

  1. ZADITOR (ketotifen fumarate ophthalmic solution 0.025%) -- Drug Facts labelU.S. Food and Drug Administration / DailyMed (NIH), OTC Drug Facts label · United States · accessed 2026-07-30 · source 1
  2. Ketotifen in the management of chronic urticaria / general pharmacy references on oral ketotifen's US regulatory historyPublished clinical/pharmacy literature (secondary, corroborating the absence of any US oral product) · United States · accessed 2026-07-30 · source 2
  3. Ketotifen Tablets (ZADITEN) 1 mg -- Product MonographHealth Canada, Product Monograph · Canada · accessed 2026-07-30 · source 3
  4. Zaditen 0.25 mg/ml eye drops, solution -- Summary of Product Characteristicselectronic medicines compendium (emc), United Kingdom -- Thea Pharmaceuticals Ltd · United Kingdom · accessed 2026-07-30 · source 4
  5. Zaditen 1mg Tablets -- Patient Information LeafletUK-licensed Patient Information Leaflet for Zaditen 1 mg Tablets (Alfasigma, MHRA-licensed), as republished by drugs.com/uk · United Kingdom · accessed 2026-07-30 · source 5
  6. Ketotifen (oral formulations) -- list of nationally authorised medicinal products, PSUSA/00001813European Medicines Agency (EMA), list of nationally authorised medicinal products · European Union · accessed 2026-07-30 · source 6
  7. ZADITEN ketotifen 250 microgram/mL eye drops -- ARTG entry 520875 (and multiple generic-brand ARTG entries)Therapeutic Goods Administration (TGA), Australia · Australia · accessed 2026-07-30 · source 7
  8. Zaditen Eye Drops 0.25 mg/mL (ketotifen) -- New Zealand Data SheetMedsafe (New Zealand regulator) · New Zealand · accessed 2026-07-30 · source 8
  9. No current, live Medsafe data sheet located for an oral ketotifen tablet/syrup productN/A -- absence-of-evidence note, not a positive source · New Zealand · accessed 2026-07-30 · source 9

Brand names by country

Single-ingredient ketotifen names are shown separately by country. Product availability, strengths, and supply rules can change; combination products are not included here.

Priority countries

United States

  • Eye Itch Relief.25 mg/mL, .35 mg/mL · safeway
  • Eye Itch Releif.25 mg/mL · rite aid corporation
  • Equate Eye Itch Relief.25 mg/mL · wal-mart stores, inc.
  • Zaditor.25 mg/mL · alcon laboratories, inc.
  • Alaway.25 mg/mL · bausch & lomb incorporated

United Kingdom

  • Zaditen (4)MHRA licensed emc smpc confirmed eyedrops · 0.25 mg/ml · Thea Pharmaceuticals Ltd
  • Zaditen (5)MHRA licensed tablets intermittent supply history · 1 mg · Alfasigma

Canada

  • ZADITEN
  • ZADITOR
  • APO-KETOTIFEN - SYR

Australia

  • Zaditen (and pharmacy-own-brand generics: Chemists' Own, Blooms The Chemist, Zoptic, Pharmacy Health, Apohealth, Priceline Pharmacy) (7)TGA ARTG registered confirmed eyedrops only · 250 microgram/mL · various ARTG sponsors

New Zealand

  • Zaditen Eye Drops (8)Medsafe registered confirmed · 0.25 mg/mL · Novartis New Zealand Limited
View brands in additional countries.

European Union

Zaditen (and national generic equivalents) (6)

This page provides general reference information about ketotifen and is not a substitute for advice from your doctor or pharmacist. Always confirm which product form (eye drops or oral tablets/syrup) applies to you and follow your own country's licensed product information.

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