Ketotifen (Zaditor)

1. Health Canada Product Monograph — Ketotifen

• Zaditor is indicated to treat allergic conjunctivitis, which causes itchy, red, watery, or swollen eyes.

• There are no clinical studies of Zaditor use in pregnant women.
• Animal studies using much higher oral doses than the eye drop dose showed increased pregnancy loss but no birth defects; Zaditor should be used during pregnancy only if the benefit justifies the potential risk to the fetus.

• It is not known whether ketotifen from eye drops passes into human breast milk, so caution is advised when using Zaditor while breastfeeding.

• There is no specific data on Zaditor use in older adults, so Health Canada has not authorized a distinct geriatric indication; standard adult dosing applies.

• Zaditor is approved for use in children over 3 years of age, at the same dose used in adults.
• In studies, Zaditor was used safely in patients as young as 3 years old, including with more frequent dosing than usually recommended, for up to 6 weeks.

• The usual dose is one drop in the affected eye or eyes every 8 to 12 hours.
• Wash your hands before use, and avoid touching the dropper tip to your eye or any other surface to prevent contamination.
• To administer, close the treated eye and gently press on the inner corner of the eye, near the nose, for 1 to 2 minutes after each drop, which helps reduce the amount absorbed into the body.
• Close the bottle tightly after each use.
• If a dose is missed, apply it as soon as possible; if it is almost time for the next dose, skip the missed dose and resume the regular schedule without doubling up.
• Zaditor begins relieving itching and redness within minutes of use, and its effect can last up to 12 hours, consistent with its dosing schedule.

If overdose is suspected, seek emergency medical attention immediately or contact your regional Poison Control Centre without delay.

• Swallowing the entire contents of a bottle would deliver only a small amount of ketotifen fumarate, and clinical experience has shown no serious symptoms even after ingestion of doses well above this amount.
• No specific treatment is described as being needed for accidental ingestion of Zaditor, but a healthcare professional or poison control centre should still be contacted if this occurs.

• Redness of the eye (conjunctival hyperemia) is the most common side effect.
• Eye irritation or pain may occur.
• Itching of the eye may occur.
• Dry eye may occur.
• Eye discharge may occur.
• Eyelid swelling or irritation may occur.
• Headache may occur.
• A feeling of something in the eye may occur.
• Blurred vision may occur.
• Enlarged pupils may occur.
• Sensitivity to light may occur.
• A broken blood vessel in the eye may occur.
• Nasal congestion, runny nose, or sneezing may occur.
• Drowsiness or dizziness may occur.
• Dry mouth may occur.
• Weakness or a general lack of energy may occur.

Serious side effects require immediate discussion with the prescriber or emergency care.

• Keratitis, an inflammation or irritation of the clear front surface of the eye, may occur.
• Small areas of irritation on the surface of the cornea, known as punctate keratitis or corneal erosion, have been reported.
• A fast heartbeat (tachycardia) has been reported rarely.
• Serious allergic reactions, including swelling of the face, lips, tongue, or throat, hives, or difficulty breathing, may occur.
• Local allergic reactions, such as contact dermatitis around the eye or eyelid swelling and itching, may occur.
• Eczema or hives (urticaria) may occur as an allergic skin reaction.
• Rarely, using Zaditor may worsen pre-existing allergic conditions such as asthma or eczema.
• Paradoxical worsening of conjunctivitis, with increased eye irritation, has been reported rarely.
• Seek urgent medical attention for signs of a severe allergic reaction, a rapid or irregular heartbeat with dizziness or shortness of breath, or worsening eye pain, redness, or discharge.

• Use with caution in people who wear soft contact lenses, since a preservative in Zaditor can be absorbed by the lenses and discolour them.
• Use with caution in patients with dry eyes or corneal disorders, since the preservative in Zaditor can cause additional eye irritation in these conditions.
• Use with caution in patients whose eye symptoms do not improve or who develop worsening pain, redness, or discharge, since these could indicate a different eye condition needing separate treatment.
• Zaditor is intended for topical eye use only and should not be injected or taken by mouth.
• Patients should be cautioned about driving or operating machinery if they experience blurred vision or drowsiness after using Zaditor.
• Use with caution alongside other eye medications; wait at least 5 minutes between different eye drops, and apply any eye ointment last.

• Contraindicated in patients with known hypersensitivity to ketotifen or to any ingredient in the formulation or its container.

• Although not clearly demonstrated with the eye drop formulation, oral forms of ketotifen can add to the sedating effects of central nervous system depressants, antihistamines, and alcohol, so this possibility cannot be fully excluded with the eye drops.
• If other eye medications are used at the same time as Zaditor, they should be spaced at least 5 minutes apart, since applying drops too close together can wash out the earlier one.
• In studies, ketotifen blood levels after twice-daily eye drop use for 14 days were mostly undetectable, suggesting the eye drops have much less potential than oral ketotifen to interact with other medicines taken by mouth.

• Zaditor is applied directly to the eye rather than swallowed, so it has no food-timing considerations for the patient.

• Zaditor is used every 8 to 12 hours as needed for allergy symptoms, rather than at a time tied to meals.

• Store Zaditor between 4°C and 25°C.
• Once opened, the bottle should be discarded after 4 weeks.
• Do not use the solution if it is discoloured or contains particles, and avoid sharing your bottle with others to prevent eye infections.

• Zaditor is an eye drop that relieves itchy, red, watery eyes from seasonal allergies; remove contact lenses before use and wait at least 15 minutes before reinserting them, and seek prompt care for worsening eye pain, vision changes, or signs of an allergic reaction.