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Ketotifen (antihistamine, anti-allergy)

Ketotifen is a type of drug known as an antihistamine. Ketotifen works by binding to histamine H-1 receptors on various cells throughout the body, including white blood cells. By blocking histamine, it prevents symptoms such as sneezing, itchiness, redness, inflammation, and runny nose.



What is ketotifen used for?

Ketotifen is used to treat the following:

  • Allergic conjunctivitis
  • Allergic rhinitis

How should I take ketotifen?

Ketotifen is available as an oral tablet, syrup, drops, and ophthalmic solution. The oral tablet, syrup, and drops should be taken by mouth. The tablet should be swallowed whole without chewing or crushing it.

The liquid preparations should be measured using the included medical-grade measuring cup or dropper. Do not use a regular household spoon, as this may not measure the correct dose.

The ophthalmic solution should be instilled into the eye(s) without touching the tip of the bottle. Always cover the nozzle after each use and during storage. If you wear contact lenses, remove the lenses prior to instilling the drops.

How do I store ketotifen?

This product is best stored at room temperature away from direct light and moisture. To prevent drug damage, you should not store it in the bathroom or the freezer.

There may be different brands of this drug that may have different storage needs. So, it is important to always check the product package for instructions on storage, or ask your pharmacist. For safety, you should keep all medicines away from children and pets.

You should not flush this product down the toilet or pour them into a drain unless instructed to do so. Additionally, it is important to properly discard this product when it is expired or no longer needed. Consult your pharmacist for more details about how to safely discard your product.

Precautions & Warnings

What should I know before using ketotifen?

Before using this drug, tell your doctor if you are/have:

  • Pregnant or breastfeeding.
  • Taking any other medicines. This includes any prescription, OTC, and herbal remedies.
  • An allergy to any of the ingredients of this product.
  • Any other illnesses, disorders, or medical conditions.

Is it safe during pregnancy or breastfeeding?

Ketotifen is a pregnancy category C drug. There are no adequate and well-controlled studies using ketotifen in pregnant women. Please always consult with your doctor to weigh the potential benefits and risks before taking any medication.

Side Effects

What side effects can occur when using ketotifen?

Like all drugs, this product may have side effects. If they occur, side effects are generally mild and resolve once treatment is finished or the dose is lowered. Some reported side effects include:

  • Drowsiness
  • Dizziness
  • Insomnia
  • Agitation, irritability
  • Nervousness
  • Eye irritation
  • Blurred vision
  • Dry mouth or eyes
  • Weight gain

Severe adverse reactions:

  • Skin rash
  • Redness
  • Blistering of the lips, eyes, or mouth
  • Fever
  • Chills
  • Headache
  • Jaundice
  • Seizure

However, not everyone experiences these side effects. In addition, some people may experience other side effects. So, if you have any concerns about a side effect, please consult your doctor or pharmacist.


What drugs may interact with ketotifen?

This medication may interact with other drugs that you are currently taking, which can change how your drug works or increase your risk for serious side effects.

To avoid any potential drug interactions, you should keep a list of all the drugs you are using (including prescription drugs, nonprescription drugs, and herbal products) and share it with your doctor and pharmacist.

Drugs with known interactions:

  • Sedatives
    • Increased symptoms of drowsiness
  • Hypnotics
    • Increased symptoms of drowsiness
  • Other antihistamines
    • Increased symptoms of drowsiness
  • Oral antidiabetics
    • Reduced platelet count (potentially fatal)

If you experience an adverse drug interaction, stop taking this drug and continue taking your other medication. Inform your doctor immediately to reevaluate your treatment plan. Approaches include dose adjustment, drug substitution, or ending therapy.

Does food or alcohol interact with ketotifen?

There are no known food interactions with ketotifen. However, it is best to take this medication with meals. Do not take ketotifen with alcohol as it may potentiate the effects of drowsiness and CNS depression.

What health conditions may interact with ketotifen?

This drug may interact with underlying conditions. This interaction may worsen your health condition or alter the way the drug works. Therefore, it is important to always let your doctor and pharmacist know all the health conditions you currently have, especially:

  • History of epilepsy
  • Diabetes mellitus


The information provided is not a substitute for any medical advice. Therefore, you should always consult with your doctor or pharmacist before using any medication.

What is the dose for an adult?

Allergic rhinitis

  • Oral preparations: Take 1 mg two times a day, increasing the dose up to 2 mg if needed.
    • Alternatively, take 0.5 to 1 mg at night for the first few days of treatment, to minimized drowsiness.

Allergic conjunctivitis

  • Ophthalmic drops: Instill 1 drop into the conjunctival sac of the affected eye(s) two times a day.

What is the dose for a child?

Allergic rhinitis

  • For children 3 years and above: The same as the adult dose.

Allergic conjunctivitis

  • For children 3 years and above: The same as the adult dose.

How is ketotifen available?

This drug is available in the following brands, dosage forms, and strengths:

  • Azimef syrup 1 mg/5 mL
  • Zadec oral infant drops solution 1 mg/ mL
  • Zaditen tablet 1 mg

What should I do in case of an emergency or overdose?

In case of an emergency or an overdose, call your local emergency services or go to the nearest emergency room.

What should I do if I miss a dose?

If you miss a dose, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and take your regular dose as scheduled. Do not take a double dose.


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Hello Health Group does not provide medical advice, diagnosis or treatment.


Ketotifen https://www.mims.com/philippines/drug/info/ketotifen?mtype=generic Accessed June 15, 2021

Ketotifen (Oral Route) https://www.mayoclinic.org/drugs-supplements/ketotifen-oral-route/description/drg-20064435 Accessed June 15, 2021

Ketotifen, https://pubchem.ncbi.nlm.nih.gov/compound/Ketotifen, Accessed June 15, 2021

Ketotifen (Systemic). Lexi-Drugs. Lexicomp. Wolters Kluwer Health, Inc. Riverwoods, IL. Accessed June 15, 2021. http://online.lexi.com

Ketotifen https://pubchem.ncbi.nlm.nih.gov/compound/Ketotifen Accessed June 15, 2021

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Written by Stephanie Nera, RPh, PharmD Updated Jun 15, 2021
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