Zaditen

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Zaditen on Prescriptsy

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Zaditen is a brand of ketotifen eye drops containing ketotifen 0.025% (0.25 mg/mL), manufactured by Thea Pharmaceuticals.

Ketotifen is a dual-action anti-allergic agent that combines mast cell stabilising activity with histamine H1 receptor antagonism, providing both prophylactic and therapeutic relief of allergic conjunctivitis.

Zaditen eye drops are licensed for the prevention and treatment of seasonal allergic conjunctivitis (triggered by pollen) and perennial allergic conjunctivitis (triggered by persistent allergens such as house dust mites, pet dander, and moulds).

Zaditen is classified as a pharmacy medicine (P) in the United Kingdom, available from pharmacies without prescription.

Allergic conjunctivitis is extremely common in the UK, affecting an estimated 15 to 20% of the population.

Seasonal allergic conjunctivitis (hay fever-related eye symptoms) affects millions of people during the pollen season (typically March to September), while perennial allergic conjunctivitis causes year-round symptoms in sensitised individuals.

The condition causes significant discomfort, reduced productivity, and impaired quality of life.

Ocular symptoms including itching, redness, tearing, and eyelid swelling are frequently the most troublesome component of allergic rhinoconjunctivitis.

This page provides a comprehensive clinical guide to Zaditen eye drops, covering how they work, dosage, side effects, safety information, and how to obtain them in the United Kingdom.

Important safety information about Zaditen eye drops

Before reading further, note these essential safety points about Zaditen.

• Remove contact lenses before instilling Zaditen drops. Wait at least 15 minutes before reinserting.
• Transient blurred vision may occur after instillation. Do not drive until your vision has cleared.
• Discard opened multidose bottles after 28 days.
• Zaditen is for allergic eye conditions only. It will not treat eye infections or contact lens irritation.
• If eye symptoms worsen or do not improve within a few days, consult your pharmacist or GP.

Understanding allergic conjunctivitis

Allergic conjunctivitis is an IgE-mediated type I hypersensitivity reaction affecting the conjunctiva (the thin, transparent membrane covering the white of the eye and the inner surface of the eyelids).

When a sensitised individual is exposed to an allergen, the allergen cross-links IgE antibodies bound to mast cells in the conjunctival tissue.

This triggers mast cell degranulation, releasing preformed mediators (primarily histamine, but also tryptase and heparin) from intracellular granules within minutes (the early phase response).

Histamine binds to H1 receptors on conjunctival blood vessels (causing vasodilation and redness), sensory nerve endings (causing itching), and goblet cells (causing mucous secretion).

Over the following 4 to 24 hours, the late phase response involves the synthesis and release of newly formed mediators including prostaglandins, leukotrienes, and cytokines, and the recruitment of inflammatory cells including eosinophils, neutrophils, and T lymphocytes to the conjunctiva, perpetuating the inflammatory response.

Seasonal allergic conjunctivitis is triggered primarily by airborne pollen: tree pollen (February to May), grass pollen (May to August, peaking in June and July), and weed pollen (June to September).

Perennial allergic conjunctivitis is triggered by house dust mite allergens (Der p 1, Der p 2), animal dander (cats, dogs), mould spores, and cockroach allergens.

The cardinal symptom is bilateral eye itching (the single most diagnostic feature of allergic conjunctivitis), accompanied by redness, watering, and mucoid discharge.

Eyelid oedema and chemosis (conjunctival swelling) may occur in more severe cases.

How Zaditen eye drops work

Ketotifen has a dual mechanism of action that provides both immediate symptomatic relief and longer-term prophylactic protection against allergic conjunctivitis.

The antihistamine action is immediate.

Ketotifen competitively binds to histamine H1 receptors on conjunctival blood vessels, sensory nerve endings, and epithelial cells, blocking the effects of histamine released during the early phase allergic response.

This rapidly reduces itching (the dominant symptom), redness, and tearing. The H1 receptor antagonism provides symptomatic relief within minutes of instillation and persists for 8 to 12 hours.

The mast cell stabilising action develops over several days of regular use.

Ketotifen inhibits the degranulation of conjunctival mast cells by stabilising the mast cell membrane, reducing the calcium influx required for granule fusion and mediator release.

It inhibits the release of histamine, tryptase, prostaglandin D2, and leukotriene C4 from mast cells.

This prophylactic effect reduces both the early and late phase allergic responses when the individual is subsequently exposed to the trigger allergen.

Additional anti-inflammatory effects include inhibition of eosinophil migration to the conjunctiva (eosinophils are key effector cells in the late phase response and in chronic allergic inflammation), suppression of interleukin-8 and tumour necrosis factor-alpha release, and inhibition of platelet-activating factor.

These broader anti-inflammatory actions contribute to the efficacy of ketotifen in more persistent allergic conjunctivitis.

Comparison with other allergy eye drops

Several categories of topical ophthalmic anti-allergy agents are available in the UK.

Pure antihistamines such as antazoline (in Otrivine-Antistin) provide rapid symptomatic relief but no prophylactic mast cell stabilising effect.

Pure mast cell stabilisers such as sodium cromoglicate 2% (Opticrom) provide good prophylactic protection when used regularly before allergen exposure but take several days to reach maximum effect and provide limited immediate symptomatic relief.

Dual-action agents such as ketotifen (Zaditen) and olopatadine (Opatanol) combine both mechanisms, offering immediate symptom relief and prophylactic protection in a single agent.

This dual activity makes them particularly convenient and effective for most patients with allergic conjunctivitis.

Ketotifen has the advantage of being available as a pharmacy medicine (P), accessible without prescription. Olopatadine (Opatanol) is a prescription-only medicine.

Sodium cromoglicate (Opticrom) is also available without prescription.

For moderate to severe allergic conjunctivitis not adequately controlled by topical agents, short courses of topical corticosteroid eye drops (such as fluorometholone or loteprednol) may be prescribed by a specialist, but these carry risks of raised intraocular pressure, cataract, and infection with prolonged use.

Dosage and administration

Instil 1 drop into each affected eye twice daily (morning and evening).

During peak allergy season or with severe symptoms, the dose may be increased to 1 drop three times daily.

For best prophylactic results, start treatment 1 to 2 weeks before the expected onset of the pollen season and continue throughout the exposure period.

Correct instillation technique maximises efficacy and minimises waste and systemic absorption. Wash hands. Tilt the head back. Pull down the lower eyelid. Look upward.

Instil 1 drop into the conjunctival sac (the pocket formed by the lower lid). Close the eye gently.

Press lightly on the inner corner of the eye (nasolacrimal punctum) for 1 to 2 minutes to reduce drainage into the nasal cavity and systemic absorption.

If using multiple eye drop preparations, wait at least 5 minutes between different drops. If using eye drops and eye ointments, apply drops first and ointment last.

Contact lens wearers should remove lenses before instillation and wait at least 15 minutes before reinserting.

Preservative-free single-dose units are available and preferred for contact lens wearers and those with dry eyes.

Side effects of Zaditen eye drops

Common side effects

Mild eye irritation, stinging, or burning on instillation is the most commonly reported side effect and typically resolves within seconds to minutes.

It does not indicate allergy and does not require stopping treatment. Eye dryness and mild eyelid swelling may occur in 1 to 10% of users.

Uncommon side effects

Transient blurred vision after instillation (lasting a few minutes), increased tearing, light sensitivity, eye pain, and headache are uncommon. Mild drowsiness may occur in rare cases due to minimal systemic absorption of ketotifen.

Preservative-related effects

Benzalkonium chloride (BAK), used as a preservative in multidose bottles, is a known ocular surface irritant with prolonged use.

It can cause punctate keratopathy (superficial corneal erosions detectable on slit-lamp examination with fluorescein staining), reduced tear film stability, and discomfort in patients with pre-existing dry eye disease.

For patients requiring long-term use, preservative-free single-dose units are recommended. Report suspected adverse reactions to the MHRA at yellowcard.mhra.gov.uk .

Warnings and precautions

When to seek further advice

Consult your pharmacist, optometrist, or GP if symptoms do not improve within a few days of starting treatment, if symptoms worsen, if you develop eye pain, significant visual disturbance, or photophobia (which may suggest a more serious eye condition such as keratitis, uveitis, or acute glaucoma), or if you develop a purulent (pus-like) discharge suggesting bacterial conjunctivitis rather than allergic conjunctivitis.

Differential diagnosis

Not all red, itchy eyes are allergic conjunctivitis. Infective conjunctivitis (bacterial or viral) typically presents with unilateral onset, purulent or mucopurulent discharge, and morning crusting.

Dry eye disease causes grittiness, burning, and fluctuating vision. Blepharitis causes eyelid margin inflammation and crusting.

Contact lens-related problems including giant papillary conjunctivitis and microbial keratitis require specific management.

Acute angle-closure glaucoma causes severe eye pain, nausea, halos around lights, and reduced vision and is a medical emergency. If in doubt about the diagnosis, seek professional assessment.

Pregnancy, breastfeeding, and children

Systemic absorption from topical ophthalmic ketotifen is minimal. Use during pregnancy and breastfeeding is considered low risk but should be discussed with a healthcare professional.

Zaditen eye drops are licensed for children aged 3 years and above at the same dose as adults.

How to get Zaditen eye drops in the UK

Zaditen eye drops are available as a pharmacy medicine (P) from any registered pharmacy without a prescription, following a consultation with the pharmacist.

They can also be obtained on NHS prescription from your GP.

The standard NHS prescription charge in England is 9.90 pounds per item; prescriptions are free in Scotland, Wales, and Northern Ireland.

For patients paying the prescription charge, purchasing Zaditen over the counter may be more cost-effective. Generic ketotifen eye drops are also available and are bioequivalent.

Sources

• Zaditen Eye Drops, Summary of Product Characteristics (EMC)
• Ketotifen, British National Formulary (BNF)
• Allergic conjunctivitis, NICE CKS
• Allergic conjunctivitis, NHS
• Clinical Management Guidelines, College of Optometrists
• MHRA Yellow Card Scheme