Medical Editor: John P. Cunha, DO, FACOEP Last updated on RxList: 6/28/2022

Drug Summary

What Is Zaditor?

Zaditor (ketotifen fumarate) Ophthalmic Solution is an antihistamine used to treat itching of the eyes caused by allergy to dust, pollen, animals, or other allergens. Zaditor is available in generic form.

What Are Side Effects of Zaditor?

Common side effects of Zaditor include:

  • burning/stinging/irritation of the eye,
  • eye dryness,
  • headache,
  • stuffy/runny nose,
  • bad taste in your mouth, and
  • increased sensitivity to light.

Tell your doctor if you have unlikely but serious side effects of Zaditor including:

  • eye pain,
  • increased redness or swelling of the eye, or
  • vision problems.

Seek medical care or call 911 at once if you have the following serious side effects:

  • Serious eye symptoms such as sudden vision loss, blurred vision, tunnel vision, eye pain or swelling, or seeing halos around lights;
  • Serious heart symptoms such as fast, irregular, or pounding heartbeats; fluttering in your chest; shortness of breath; and sudden dizziness, lightheartedness, or passing out;
  • Severe headache, confusion, slurred speech, arm or leg weakness, trouble walking, loss of coordination, feeling unsteady, very stiff muscles, high fever, profuse sweating, or tremors.

This document does not contain all possible side effects and others may occur. Check with your physician for additional information about side effects.

Dosage for Zaditor

The dose of Zaditor for adults and children 3 years of age and older: Put 1 drop in the affected eye(s) twice daily, every 8-12 hours, no more than twice per day.

What Drugs, Substances, or Supplements Interact with Zaditor?

Other drugs may interact with Zaditor ophthalmic. Tell your doctor about all the prescription and over-the-counter medications and supplements you use.

Zaditor During Pregnancy and Breastfeeding

During pregnancy, Zaditor should be used only when prescribed. It is not known whether this drug passes into breast milk. Consult your doctor before breastfeeding.

Additional Information

Our Zaditor (ketotifen fumarate) Ophthalmic Solution Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.

Drug Description

Now available Over-The-Counter (OTC); No prescription needed.


Zaditor® (ketotifen fumarate) is an antihistamine eye drop to relieve itchy eyes due to allergens.

ZADITOR® (ketotifen fumarate) is a sterile ophthalmic solution containing ketotifen for topical administration to the eyes. Ketotifen fumarate is a finely crystalline powder with an empirical formula of C23H23NO5S and a molecular weight of 425.50.


Established Name: Ketotifen Fumarate Ophthalmic Solution

Chemical Name: 4-(1-Methyl-4-piperidylidene)-4H-benzo[4,5]cyclohepta[1,2-b] thiophen-10(9H)-one hydrogen fumarate

Each mL of ZADITOR (ketotifen fumarate) &reade; contains:

Active: 0.345 mg ketotifen fumarate equivalent to 0.25 mg ketotifen.

Inactives: glycerol, sodium hydroxide/hydrochloric acid (to adjust pH) and purified water.

Preservative: benzalkonium chloride 0.01%. It has a pH of 4.4 to 5.8 and an osmolality of 210-300 mOsm/kg.

Indications & Dosage


ZADITOR® (ketotifen fumarate ophthalmic solution) is indicated for the temporary prevention of itching of the eye due to allergic conjunctivitis.


Adults and children 3 years of age and older: Put 1 drop in the affected eye(s) twice daily, every 8-12 hours, no more than twice per day.

Children under 3 years of age: Consult a doctor.


ZADITOR (ketotifen fumarate) comes in a 5 ml bottle that contains a 30-day supply if dosed as directed.


Store at 4°- 25° C (39°- 77° F).

Novartis Pharmaceuticals Corporation
One Health Plaza
East Hanover, New Jersey 07936-1080

Side Effects & Drug Interactions


In controlled clinical studies, conjunctival injection, headaches, and rhinitis were reported at an incidence of 10 to 25%. The occurrence of these side effects was generally mild. Some of these events were similar to the underlying ocular disease being studied.

The following ocular and non-ocular adverse reactions were reported at an incidence of less than 5%:

Ocular: Allergic reactions, burning or stinging, conjunctivitis, discharge, dry eyes, eye pain, eyelid disorder, itching, keratitis, lacrimation disorder, mydriasis, photophobia, and rash.

Non-Ocular: Flu syndrome, pharyngitis.


No information provided.

Warnings & Precautions


For topical ophthalmic use only. Not for injection or oral use.



Carcinogenesis, Mutagenesis, Impairment of Fertility

Ketotifen fumarate was determined to be non-mutagenic in a battery of in vitro and in vivo mutagenicity assays including: Ames test, in vitro chromosomal aberration test with V79 Chinese hamster cells, in vivo micronucleus assay in mouse, and mouse dominant lethal test.

Treatment of male rats with oral doses of ketotifen ³10 mg/kg/day orally [6,667 times the maximum recommended human ocular dose of 0.0015 mg/kg/day on a mg/kg basis (MRHOD)] for 70 days prior to mating resulted in mortality and a decrease in fertility. Treatment with ketotifen did not impair fertility in female rats receiving up to 50 mg/kg/day of ketotifen orally (33,333 times the MRHOD) for 15 days prior to mating.


Pregnancy Category C

Oral treatment of pregnant rabbits during organogenesis with 45 mg/kg/day of ketotifen (30,000 times the MRHOD) resulted in an increased incidence of retarded ossification of the sternebrae. However, no effects were observed in rabbits treated with up to 15 mg/kg/day (10,000 times the MRHOD). Similar treatment of rats during organogenesis with 100 mg/kg/day of ketotifen (66,667 times the MRHOD) did not reveal any biologically relevant effects.

Oral treatment of pregnant rats (up to 100 mg/kg/day or 66,667 times the MRHOD) and rabbits (up to 45 mg/kg/day or 30,000 times the MRHOD) during organogenesis did not result in any biologically relevant embryofetal toxicity. In the offspring of the rats that received ketotifen orally from day 15 of pregnancy to day 21 post partum at 50 mg/kg/day (33,333 times the MRHOD), a maternally toxic treatment protocol, the incidence of postnatal mortality was slightly increased, and body weight gain during the first four days post partum was slightly decreased.

Nursing Mothers

Ketotifen fumarate has been identified in breast milk in rats following oral administration. It is not known whether topical ocular administration could result in sufficient systemic absorption to produce detectable quantities in breast milk. Nevertheless, caution should be exercised when ketotifen fumarate is administered to a nursing mother.

Pediatric Use

Safety and effectiveness in pediatric patients below the age of 3 years have not been established.

Overdose & Contraindications


Oral ingestion of the contents of a 5 mL bottle would be equivalent to 1.725 mg of ketotifen fumarate. Clinical results have shown no serious signs or symptoms after the ingestion of up to 20 mg of ketotifen fumarate.


ZADITOR® (ketotifen fumarate) is contraindicated in persons with a known hypersensitivity to any component of this product.

Clinical Pharmacology


Ketotifen is a relatively selective, non-competitive histamine antagonist (H1-receptor) and mast cell stabilizer. Ketotifen inhibits the release of mediators from cells involved in hypersensitivity reactions. Decreased chemotaxis and activation of eosinophils has also been demonstrated.

Ketotifen has been shown to have little systemic exposure following topical ocular administration. A study conducted with 15 healthy volunteers dosed bilaterally with ketotifen fumarate ophthalmic solution twice daily for 14 days demonstrated plasma concentrations generally below the quantitation limit of assay (< 20 pg/mL).

In human conjunctival allergen challenge studies, ZADITOR® (ketotifen fumarate) was significantly more effective than placebo in preventing ocular itching associated with allergic conjunctivitis. The action of ketotifen occurs rapidly with an effect seen within minutes after administration.

Medication Guide


What is Zaditor?
Zaditor (ketotifen fumarate ophthalmic solution 0.025%) is an over-the-counter (OTC) antihistamine eye drop that relieves itchy eyes due to allergens. It's the first OTC eye drop strong enough to last up to 12 hours with just one drop. Previously available only with a prescription, Zaditor (ketotifen fumarate) is now available OTC in original prescription strength.

What is the difference between Zaditor (ketotifen fumarate) and leading OTC antihistamine eye drops?
With Zaditor (ketotifen fumarate) , you can expect fast, effective relief with just one drop that lasts up to 12 hours, whereas the leading OTC eye drops only provide relief for up to 4-6 hours. Some OTC itchy eye products also contain redness relievers (vasoconstrictors) that through repeated use can actually cause your eyes to become even redder after the effect of the vasoconstrictor wears off. This is called the "rebound effect." Zaditor (ketotifen fumarate) works differently from these types of products. It stops the itch at the source by also blocking histamines (a chemical made by the body during an allergic reaction) that causes itchy eyes but does not directly constrict blood vessels. With Zaditor (ketotifen fumarate) , you don't have to worry about worsening your symptoms as a result of the "rebound effect."

Why did Novartis Ophthalmics apply to the FDA to change Zaditor (ketotifen fumarate) from prescription to OTC?
Since its introduction in the U.S. in 1999, Zaditor (ketotifen fumarate) has been safely used by millions for the temporary prevention of itchy eyes due to allergic conjunctivitis. By making Zaditor (ketotifen fumarate) available OTC, itchy eye sufferers can experience fast, long-lasting relief from itchy eyes without a prescription.

Is OTC Zaditor (ketotifen fumarate) the same strength as original prescription-strength Zaditor (ketotifen fumarate) ?
Yes. You can now benefit from the same prescription-strength Zaditor (ketotifen fumarate) without a prescription.

How safe is Zaditor (ketotifen fumarate) ?
The FDA has determined that Zaditor (ketotifen fumarate) is safe for OTC use based on the long-term use of the drug, as well as the controlled clinical studies that supported the original prescription-strength formula.

Is Zaditor (ketotifen fumarate) safe for use in children?
Yes. Zaditor (ketotifen fumarate) is safe for children as young as 3 years old.

Can Zaditor (ketotifen fumarate) be used in both eyes?
Zaditor (ketotifen fumarate) should only be applied to the eye or eyes that are affected.

How is Zaditor (ketotifen fumarate) administered?
The recommended dose is one drop in the affected eye(s) twice daily.

Can Zaditor (ketotifen fumarate) be used with contact lenses?
Yes. However, contact lenses should be removed prior to applying Zaditor (ketotifen fumarate) and not reinserted for at least 10 minutes following application.

Does Zaditor (ketotifen fumarate) treat seasonal allergic conjunctivitis?
Zaditor (ketotifen fumarate) relieves itchy eyes caused by seasonal allergic conjunctivitis.

Does Zaditor (ketotifen fumarate) treat perennial allergic conjunctivitis?
Zaditor (ketotifen fumarate) relieves itchy eyes caused by perennial allergic conjunctivitis.

Does Zaditor (ketotifen fumarate) treat pink eye?
Zaditor (ketotifen fumarate) relieves the symptoms of allergic conjunctivitis, which is a type of pink eye. Other causes of pink eye include infectious (viral, bacterial and fungal), inflammatory (rheumatoid arthritis, systemic lupus erythematosus, etc) and toxic (chemical and other irritants). Always consult your health-care professional for proper diagnosis and treatment.

How much does Zaditor (ketotifen fumarate) cost?
Suggested retail price for a 30-day supply is $14.99.

Is Zaditor (ketotifen fumarate) covered by insurance?
Typically, OTC medications are not covered by health insurance.

What are some of the causes of itchy eyes?
Itchy eyes can be caused by seasonal or perennial allergens such as pollen, ragweed, mold, dust, animal hair and pet dander. Worsening or prolongation of symptoms should be seen by a medical professional.

When and where will Zaditor (ketotifen fumarate) be available OTC?
Zaditor (ketotifen fumarate) has been available OTC in retail stores since January 2007.

What is the preservative in Zaditor (ketotifen fumarate) ?
The preservative in Zaditor (ketotifen fumarate) is benzalkonium chloride.

How should Zaditor (ketotifen fumarate) be stored?
Zaditor (ketotifen fumarate) should be stored at temperatures between 39° and 77° F.

What size is the Zaditor (ketotifen fumarate) bottle?
Zaditor (ketotifen fumarate) comes in a 5 ml bottle that contains a 30-day supply if dosed as directed.

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