Zaditen: Uses, Dosage & Side Effects

What Is Zaditen and What Is It Used For?

Zaditen eye drops contain the active substance ketotifen (present as ketotifen fumarate at a concentration of 0.345 mg/ml, equivalent to 0.25 mg/ml of ketotifen). Ketotifen belongs to the pharmacological class of antiallergic agents and is specifically designed for topical ophthalmic use. It is one of the most widely used over-the-counter treatments for allergic conjunctivitis worldwide and has been trusted by patients and healthcare professionals for decades.

Allergic conjunctivitis is an inflammatory condition of the conjunctiva (the thin, transparent membrane that covers the white part of the eye and the inner surface of the eyelids) caused by an immune-mediated hypersensitivity reaction to environmental allergens. The most common triggers include tree, grass, and weed pollens (causing seasonal allergic conjunctivitis, often associated with hay fever), as well as house dust mites, pet dander, and mold spores (which can cause perennial, or year-round, allergic conjunctivitis). When these allergens come into contact with the conjunctival surface, they trigger an IgE-mediated immune response that leads to mast cell degranulation and the release of histamine and other inflammatory mediators.

Zaditen addresses this allergic cascade through a dual mechanism of action that sets it apart from many other ophthalmic allergy medications. First, ketotifen acts as a selective, non-competitive antagonist at histamine H1 receptors in the conjunctival tissue. By blocking these receptors, it prevents histamine from binding and causing the characteristic symptoms of allergic conjunctivitis: itching, redness, tearing, and swelling. This antihistamine action provides rapid symptom relief, often within minutes of application. Second, ketotifen stabilizes mast cells, the immune cells responsible for releasing histamine and other pro-inflammatory mediators such as leukotrienes, prostaglandins, and platelet-activating factor (PAF). This mast cell stabilizing effect inhibits the initial allergic response before it begins, providing prophylactic protection that builds up over several days of consistent use.

The combination of these two mechanisms makes Zaditen particularly effective for the management of seasonal allergic conjunctivitis. Patients experience both immediate symptomatic improvement and a gradual reduction in the frequency and severity of allergic episodes with regular use. Clinical trials have demonstrated that ketotifen ophthalmic solution significantly reduces ocular itching, redness, and tearing compared to placebo, with efficacy comparable to or exceeding that of other topical antihistamines and mast cell stabilizers used as monotherapy.

Ketotifen, the active ingredient in Zaditen, may also be approved for other conditions not mentioned in the patient information leaflet. If you have additional questions about the use of ketotifen, consult your doctor, pharmacist, or other qualified healthcare professional and always follow their instructions. You should speak with a healthcare provider if your symptoms do not improve or if they worsen within a few days of starting treatment.

What Should You Know Before Using Zaditen?

Before using Zaditen eye drops, it is important to understand the situations in which the product should not be used, as well as the precautions that should be observed to ensure safe and effective treatment. While Zaditen is generally well-tolerated and available without a prescription, certain individuals and circumstances require special consideration.

Contraindications

Do not use Zaditen eye drops if you are allergic (hypersensitive) to ketotifen or to any of the other ingredients contained in the formulation. The excipients include benzalkonium chloride (preservative), glycerol (E 422), sodium hydroxide (E 524), and water for injections. If you have previously experienced an allergic reaction to any of these substances, whether in Zaditen or in another product, you should avoid using this medication and consult your pharmacist or doctor about alternative treatments.

Warnings and Precautions

Talk to your doctor, pharmacist, or nurse before using Zaditen if you have any pre-existing eye conditions, particularly dry eyes or problems with the cornea (the clear front surface of the eye). Benzalkonium chloride, the preservative used in Zaditen, can be irritating to the eyes, especially in individuals with corneal surface abnormalities or dry eye syndrome. If you experience irritation, stinging, or pain in the eye after applying the medication, contact your healthcare provider promptly.

If you are using other ophthalmic (eye) medications at the same time as Zaditen, you should leave at least 5 minutes between the application of each product. This interval ensures that the first medication has been adequately absorbed and is not washed out by the subsequent drop. Applying multiple eye drops in rapid succession can dilute the medications and reduce their effectiveness.

Drug Interactions

Although the systemic absorption of ketotifen from ophthalmic use is minimal, it is important to inform your doctor or pharmacist about all medications you are currently taking, have recently taken, or might take. This is particularly important for the following drug classes:

• Oral antihistamines (used for allergies): Using Zaditen eye drops alongside oral antihistamines may lead to additive sedative effects. While the systemic absorption from eye drops is low, some patients may experience increased drowsiness when combining these medications.
• Medications for depression, anxiety, or sleep disorders (including benzodiazepines, tricyclic antidepressants, and SSRIs): These medications can cause sedation and, when used together with ketotifen, there is a theoretical risk of enhanced central nervous system (CNS) depression.
• Alcohol: Zaditen may enhance the effects of alcohol. It is advisable to exercise caution when consuming alcoholic beverages while using Zaditen, as the combination may increase drowsiness or impair your ability to perform tasks requiring alertness.

Pregnancy and Breastfeeding

If you are pregnant, think you may be pregnant, or are planning to have a baby, consult your doctor or pharmacist before using Zaditen. There is limited clinical data on the use of topical ophthalmic ketotifen during pregnancy in humans. Although the systemic exposure from eye drops is expected to be very low, as a precautionary measure, Zaditen should only be used during pregnancy when clearly needed and when the potential benefit justifies any potential risk to the fetus.

Zaditen eye drops can be used during breastfeeding. The amount of ketotifen absorbed systemically from ophthalmic administration is minimal, and the quantity excreted into breast milk is expected to be negligible. Nevertheless, if you are breastfeeding and have any concerns, discuss them with your healthcare provider.

Driving and Operating Machinery

Some patients may experience transient blurred vision, fatigue, or dizziness after applying Zaditen eye drops. If you notice any of these effects, wait until your vision has cleared and the symptoms have subsided before driving a vehicle or operating machinery. You are responsible for assessing whether you are fit to drive or perform activities that require alertness. The medication's effects and side effects are described throughout this article; read all the information carefully for guidance, and discuss any concerns with your doctor or pharmacist.

What Is the Correct Dosage of Zaditen?

Always use Zaditen exactly as described in the patient information leaflet or as directed by your doctor, pharmacist, or nurse. If you are unsure about any aspect of the dosing instructions, ask your healthcare professional for clarification before starting treatment.

Adults and Elderly

Children

How to Apply Zaditen Eye Drops

Correct application technique is essential for ensuring that the medication reaches the conjunctival tissue effectively while minimizing waste and the risk of contamination. Follow these steps carefully:

1. Wash your hands thoroughly with soap and water before handling the eye drop bottle.
2. Open the bottle by unscrewing the cap. Do not touch the tip of the dropper after opening, as this could introduce bacteria and contaminate the solution.
3. Tilt your head back and look upward toward the ceiling.
4. Gently pull down your lower eyelid with one finger to create a small pocket between the eyelid and the eye.
5. Hold the bottle in your other hand, invert it, and gently squeeze to release one drop into the pocket formed by the lower eyelid. Avoid touching the eye or eyelid with the tip of the bottle.
6. Close your eye and press a fingertip gently against the inner corner of the eye (near the nose) for approximately 1–2 minutes. This technique, called punctal occlusion, prevents the drop from draining into the nasolacrimal duct and being absorbed systemically through the nasal mucosa. It also helps to keep a greater proportion of the medication in contact with the conjunctival tissue, improving local efficacy.
7. Repeat steps 3–6 for the other eye, if needed.
8. Replace the cap securely on the bottle immediately after use.

Missed Dose

If you forget to apply your Zaditen eye drops at the scheduled time, apply them as soon as you remember, and then continue with your regular dosing schedule. Do not apply a double dose (two drops at once) to make up for a missed dose, as this will not improve efficacy and may increase the risk of side effects such as eye irritation.

Overdose

There is no significant risk if a few drops of Zaditen accidentally enter the mouth, as the amount of ketotifen in the eye drop solution is very small. Similarly, there is no cause for concern if more than one drop is accidentally instilled into the eye. If a large quantity of the solution is accidentally swallowed (for example, if a child ingests the contents of the bottle), contact a poison control center, emergency department, or your healthcare provider for an assessment of risk and appropriate guidance.

What Are the Side Effects of Zaditen?

Like all medicines, Zaditen eye drops can cause side effects, although not everyone who uses them will experience them. The majority of side effects associated with Zaditen are mild and localized to the eyes, reflecting the topical route of administration and the low systemic absorption of ketotifen from ophthalmic use. Most side effects resolve on their own without the need for medical intervention.

The following side effects have been reported by patients and in clinical studies with Zaditen eye drops. They are organized by frequency using the standard medical classification system:

Most of the ocular side effects (eye irritation, transient blurred vision, mild stinging on application) are temporary and typically resolve within a few minutes. The preservative benzalkonium chloride in the formulation may contribute to eye irritation, particularly in individuals with dry eyes or compromised corneal surfaces. If you experience persistent or worsening eye symptoms, discontinue use and consult a healthcare professional.

Systemic side effects (drowsiness, headache, dry mouth, skin rash) are uncommon because very little ketotifen is absorbed into the bloodstream from topical ophthalmic application. However, patients who are particularly sensitive to antihistamines or who are using additional antihistamine medications may notice these effects more readily.

Reporting Side Effects

It is important to report suspected side effects after the medicine has been authorized for use. Reporting helps to continuously monitor the benefit-risk balance of medicines. You can report suspected side effects to your national medicines regulatory authority (for example, the FDA in the United States, the MHRA in the United Kingdom, or the EMA in the European Union) or to the manufacturer.

How Should You Store Zaditen?

Proper storage of Zaditen eye drops is essential to maintain the sterility, stability, and efficacy of the product throughout its use. Although the bottle itself is not sterile externally, the contents are sterile until the bottle is first opened. Once opened, the risk of microbial contamination increases with each use, which is why a strict 4-week use-by period applies.

Follow these storage guidelines carefully:

• Temperature: Store at or below 25°C (77°F). Do not freeze. Do not store in direct sunlight or near sources of heat.
• After opening: Use the eye drops within 4 weeks (28 days) of first opening the bottle. After this period, discard any remaining solution, even if the bottle still contains medication. Write the date of opening on the bottle to help you track this period.
• Keep out of reach of children: Store the product where young children cannot access it.
• Expiration date: Do not use Zaditen after the expiration date (indicated as "EXP" on the carton and bottle). The expiration date refers to the last day of the stated month.
• Disposal: Do not dispose of medicines by pouring them down the drain or throwing them into household waste. Ask your pharmacist about the proper way to dispose of medications that are no longer needed. These measures help protect the environment.

Each bottle of Zaditen contains 5 ml of solution. At the recommended dosage of one drop per eye twice daily, a single bottle should provide approximately 4 weeks of treatment, aligning well with the 28-day post-opening use period. If you notice any change in the appearance of the solution (such as cloudiness, discoloration, or visible particles), do not use it and obtain a new bottle.

What Does Zaditen Contain?

Understanding the full composition of Zaditen eye drops can help you identify potential allergens or ingredients that may not be suitable for your individual needs. The formulation has been carefully designed to provide a stable, sterile ophthalmic solution with an appropriate pH and osmolality for comfortable application to the eye.

Active Ingredient

The active substance is ketotifen, present as ketotifen fumarate. Each milliliter of Zaditen eye drop solution contains 0.345 mg of ketotifen fumarate, which corresponds to 0.25 mg of ketotifen base. Ketotifen fumarate is the salt form used to improve the solubility and stability of the active compound in aqueous solution.

Inactive Ingredients (Excipients)

Physical Description

Zaditen eye drops are supplied as a clear, colorless to slightly yellow solution in a 5 ml plastic dropper bottle. The bottle is equipped with a controlled-drop tip designed to dispense a consistent volume with each squeeze. Each bottle is packaged in a cardboard carton along with the patient information leaflet.

International Availability

Zaditen eye drops are authorized and marketed in numerous countries throughout the European Economic Area (EEA) and beyond. The product is marketed under the same brand name "Zaditen" in most European countries, including Austria, Denmark, Finland, Germany, Iceland, Ireland, Luxembourg, Norway, Portugal, Spain, the Netherlands, and the United Kingdom. In the United States, ketotifen ophthalmic solution is available under the brand name Zaditor (among others) as an over-the-counter product. The marketing authorization holder for Zaditen in Europe is Laboratoires Théa (Clermont-Ferrand, France), and the product is manufactured by Excelvision (Annonay, France).