Zaditor (Ketotifen) - Ophthalmic

What Is Zaditor?

Zaditor (ketotifen) is an ophthalmic solution used to treat the itching and irritation caused by allergic conjunctivitis in people 3 and older. It is available as an over-the-counter (OTC) medication that comes as a solution (a liquid) to instill in the eye.

Conjunctivitis itself is the inflammation or infection of the conjunctiva. This is the clear membrane that covers the white part of your eye.

Zaditor is an antihistamine eye drop. Antihistamines are a very common class of drugs used to treat allergies. They work by blocking a chemical known as histamine that your immune system releases when it faces an allergen.

Preventing this chemical from attaching to receptors on your eyes, nose, and respiratory tract can help relieve symptoms like eye itching, redness, and watering, as well as nasal symptoms like runny nose and sneezing.

Zaditor can be purchased over-the-counter (OTC) as a medication to be administered via eye drops. OTC means that you do not need a prescription for it from a healthcare provider. You can buy it from a drugstore or grocery store.

Zaditor is also available and will likely cost less than the generic version, called ketotifen fumarate ophthalmic solution. The same primary ingredient in Zaditor is also available in other similar brand drugs.

Drug Facts

Generic Name: Ketotifen

Brand Name: Zaditor, Alaway, Children's Alaway

Drug Availability: OTC

Therapeutic Classification: Antihistamine

Available Generically: Yes

Controlled Substance: N/A

Administration Route: Ophthalmic

Active Ingredient: Ketotifen fumarate ophthalmic solution

Dosage Form: Eye drop liquid solution

What Is Zaditor Used For?

Zaditor is Food and Drug Administration (FDA)-approved to treat itching caused by allergic conjunctivitis, or eye allergies. Allergic conjunctivitis causes symptoms including watering, itching, redness, soreness, and stinging of the eyes.

Causes of other types of conjunctivitis include chemical exposure, a virus (viral conjunctivitis), or bacteria (bacterial conjunctivitis). Zaditor will not treat viral or bacterial eye infections.

Since conjunctivitis can have several causes, you’ll want to see a healthcare provider to ensure you get the proper treatment if Zaditor does not help your symptoms. A personal history of allergies, as well as experiencing symptom relief from Zaditor, are good signs that your eye irritation is allergic.

How to Take Zaditor

Always wash your hands before using eye drops. If you are a contact lens wearer, remove your lenses before using Zaditor. There is a preservative in the drops called benzalkonium chloride, which may be absorbed by soft contacts.

Therefore, you should wait at least 10 minutes after using Zaditor drops to put your contacts in. Zaditor should not be used to treat eye irritation that is due to contact lenses.

Use your thumb and index finger to gently pull your lower eyelid down and form a pocket. Place a drop into this pouch formed in the lower lid, not directly onto your eyeball.

Be careful not to touch the tip of the dropper bottle to your eye or fingers. You can close your eyes for one to three minutes to make sure the medicine is absorbed.

Storing Zaditor

Store your Zaditor bottle in the refrigerator or at room temperature (39 to 77 degrees F) with the lid closed tightly. Do not leave Zaditor out in the heat or direct sunlight. Do not freeze the dropper bottle.

If you’re traveling by plane, keep your eyedrops in your carry-on luggage if your checked baggage goes missing.

How Long Does Zaditor Take to Work?

Zaditor works to relieve eye itching within minutes of using it. If it does not help your eye symptoms or makes them worse, you’ll want to contact your healthcare provider to see if a different treatment may be needed.

What Are the Side Effects of Zaditor?

This is not a complete list of side effects, and others may occur. A healthcare provider can advise you on side effects. If you experience other effects, contact your pharmacist or a healthcare provider. You may report side effects to the FDA at or 1-800-FDA-1088.

Common Side Effects

If you experience any of these effects and feel like they are severe or they do not go away, or if your eye symptoms worsen, stop use and contact your healthcare provider if necessary:

Severe Side Effects

The following are some potentially more serious side effects, but these occurred in less than 5% of people in Zaditor clinical trials.

  • Eye pain or stinging
  • Discharge from the eyes
  • Lacrimation disorder, or excessive tears
  • Eye redness
  • Reduced visual acuity, an impairment, or negative change in your vision
  • Photophobia (increased sensitivity to light)

Call your healthcare provider right away if you have serious side effects. Call 911 if your symptoms feel life-threatening or if you think you’re having a medical emergency.

Report Side Effects

Zaditor may cause other side effects. Call your healthcare provider if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your healthcare provider may send a report to the FDA's MedWatch Adverse Event Reporting Program or by phone (800-332-1088).

Dosage: How Much Zaditor Should I Take?

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The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

  • For ophthalmic dosage form (eye drops):
    • For prevention of itching of the eye due to allergic conjunctivitis (eye allergy):
      • Adults and children 3 years of age and older—Use one drop in each affected eye every 8 to 12 hours.
      • Children up to 3 years of age—Use and dose must be determined by your doctor.


Users should be aware of the following before beginning Zaditor:

In pregnancy and nursing: It is not well known or well studied whether Zaditor poses a risk in human pregnancy or if it shows up in human breast milk. Therefore, it should be used during pregnancy or when nursing only if the benefit of treatment outweighs any potential risk to the fetus or infant.

In pediatrics: Zaditor has been proven safe and effective in children 3 years and older.

In older adults: No studies have indicated any necessary dosing adjustments for those 65 and older.

Missed Dose

Whether you have seasonal or year-round allergies, you can use Zaditor twice a day while your eye allergies are bothering you. That schedule will give you the best chance of preventing eye symptoms.

If you forget to use a dose one morning or evening, you can use it as soon as you remember. But if it’s closer to the time of your next use than your missed one, skip that dose and wait for your next scheduled one.

Overdose: What Happens If I Take Too Much Zaditor?

It would be very difficult to overdose on Zaditor eye drops. Ingesting an entire 5-milliliter bottle of drops by mouth would be equivalent to taking 1.725 milligrams of ketotifen. Clinical studies have demonstrated no serious signs or symptoms after oral ingestion of up to 20 milligrams.

Using too many drops in the eye may be more likely to lead to side effects such as headaches or eye irritation. However, if you use Zaditor only as directed, you shouldn’t be concerned about using too much or overdosing.

What Happens If I Overdose on Zaditor?

If you think you or someone else may have overdosed on Zaditor, call a healthcare provider or the Poison Control Center (800-222-1222).

If someone collapses or isn't breathing after taking Zaditor, call 911 immediately.


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If your symptoms do not improve or if your condition becomes worse, check with your doctor.

What Are Reasons I Shouldn't Take Zaditor?

You shouldn’t use Zaditor if you have a known hypersensitivity or allergy to its contents, including ketotifen or the preservative benzalkonium chloride.

What Other Medications May Interact With Zaditor?

Since Zaditor is an eye drop, you are receiving a very small dose of medicine; therefore, very little gets absorbed into your system to potentially interact with other drugs you take by mouth.

If you use other eye drops, wait at least five minutes after using Zaditor before instilling other drops.

What Medications Are Similar to Zaditor?

Ketotifen is not the only eye medicine available to treat allergic conjunctivitis.

A few other eye drop products that treat allergies include:

  • Alaway (ketotifen) contains the same antihistamine ingredient as Zaditor but under a different brand name.
  • Pataday (olopatadine) ophthalmic solution is another antihistamine drop used twice daily.
  • Visine-A (naphazoline/pheniramine) allergy relief eye drops contain an antihistamine and a decongestant to treat itching and eye redness.
  • Alrex (loteprednol) is a corticosteroid eye drop rather than an antihistamine. It is used to treat swelling and pain caused by eye surgery but also for eye allergies.

This is a list of drugs also used for allergic conjunctivitis. It is not a list of drugs recommended to take with Zaditor, although you may try different antihistamine eye drops to find one that most helps your symptoms.

Ask your pharmacist or a healthcare provider if you have questions.

Frequently Asked Questions

  • What is Zaditor used for?

    Zaditor is an antihistamine eye drop used to treat itching due to allergic conjunctivitis or eye allergies. Zaditor should not be used to treat viral, bacterial, or chemical conjunctivitis.

  • How does Zaditor work?

    Zaditor is an antihistamine eye drop. It works by blocking a chemical called histamine that gets released by your immune system when it comes into contact with an allergen such as pollen, animal dander, and dust mites. Blocking this chemical from attaching to the receptors in your eyes, nose, and throat can relieve symptoms like itching, redness, runny nose, and sneezing.

  • What are the side effects of Zaditor?

    Common side effects of Zaditor include headache, dry eyes, sore throat, and cold-like nasal symptoms like a stuffy or runny nose.

    More rare but potentially more serious effects include eye discharge or excess tearing (lacrimation disorder), eye pain, stinging or redness, and vision changes, including increased sensitivity to light or photophobia.

How Can I Stay Healthy While Taking Zaditor?

Allergic conjunctivitis is extremely common, affecting up to 40% of the American population. Eye allergies can be not only very uncomfortable but debilitating and detrimental to the quality of life.

Though it is not a life-threatening condition, it can still majorly affect activities of daily living, especially if you are also a contact lens wearer dealing with not only allergies but potential additional irritation from your contacts.

Fortunately, many treatment options exist for eye allergies, including antihistamines, corticosteroids, immunomodulatory treatments, and non-steroidal anti-inflammatory eye drops. As you treat your eye allergies, keep your hands clean, and don’t touch the tip of the dropper on your hands, eyes, or any other surface.

Don’t wear contact lenses during a particularly bad flare-up, especially if your eyes are red. Make sure to put in new contacts as often as directed to avoid additional irritation from old lenses.

If you find that the treatments you purchase OTC are not providing you enough relief, seek advice from your healthcare provider to find a treatment more tailored to you and your symptoms.

Medical Disclaimer

Verywell Health's drug information is meant for educational purposes only and is not intended to replace medical advice, diagnosis, or treatment from a healthcare provider. Consult your healthcare provider before taking any new medication(s). IBM Watson Micromedex provides some of the drug content, as indicated on the page.

3 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Food and Drug Administration. Zaditor (ketotifen) prescribing information.

  2. Dupuis P, Prokopich CL, Hynes A, Kim H. A contemporary look at allergic conjunctivitis. Allergy Asthma Clin Immunol. 2020;16:5. doi:10.1186/s13223-020-0403-9

  3. Scadding GK. Optimal management of allergic rhinitis. Arch Dis Child. 2015;100(6):576-82.

By Sara Hoffman, PharmD
Sara is a clinical pharmacist that believes everyone should understand their medications, and aims to achieve this through her writing.