Ketotifen
Ophthalmic antiallergics
Ophthalmic antiallergics
An antihistamine eye drop that also steadies mast cells. It relieves the itch of allergic conjunctivitis for several hours.
Quick facts
- Group
- Ophthalmic antiallergics
- Target
- Histamine H1 receptor (plus mast cell stabilisation)
- Used for
- Itching of allergic conjunctivitis
- Key effects
- Burning or stinging of the eye · Headache · Dry eye
- Monitor
- Relief of itching · Eye pain or vision change
- ATC
- S01GX08
No doses: the clinician sets them by the current guideline.
Mechanism of action
The figure shows desloratadine, another H1 antihistamine, in the human H1 receptor; ketotifen blocks the same receptor.
Ketotifen blocks histamine H1 receptors in the conjunctiva and reduces mediator release from mast cells. Blocking histamine relieves itching quickly; the mast cell action helps limit further allergic symptoms.
- Ketotifen blocks conjunctival H1 receptors
- It also lowers mast cell mediator release
- Itching eases within minutes
Indications
- Itching of allergic conjunctivitis Conjunctivitis →
Adverse effects
Common
- Burning or stinging of the eye
- Headache, runny nose
- Dry eye, eye discharge, light sensitivity
- Blurred vision
Contraindications
- Hypersensitivity to ketotifen or any component
- Not for contact-lens irritation
Key interactions
- Other eye drops
- Spaced a few minutes apart so they are not washed out
What is monitored
- Relief of itching
- Eye pain or vision change
Administration and safety
- Contact lenses come out before the drop and go back in at least 10 minutes later; no lenses while the eye is red.
- The bottle tip should not touch any surface; the cap is replaced after use.
- A solution that changes colour or turns cloudy is not used.
- Oral ketotifen exists in some countries for other uses; the eye drop is a separate product.
Pregnancy and breastfeeding
Human data are limited; with little systemic absorption from the eye, it is used only if the benefit justifies the risk.
Nursing care
- Confirm the problem is allergic itching, not pain or loss of vision.
- Teach drop technique and lens removal.
- Teach to seek review if itching worsens or lasts more than a few days.
Pharmacokinetics
- Onset and duration
- Relief within minutes, lasting several hours
Test yourself
Think of the answer, then tap the question to see it.
Which receptor does ketotifen block?
The histamine H1 receptor.
Besides H1 blockade, what else does it do?
It reduces mediator release from mast cells.
Should it be used for contact-lens irritation?
No; it treats allergic itching only.
Connections
← Back to the class: Ophthalmic antiallergics
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: DailyMed - KETOTIFEN FUMARATE OPHTHALMIC SOLUTION- ketotifen fumarate solution/ drops (DailyMed (U.S. National Library of Medicine), 2026); Ketotifen Ophthalmic: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026); RCSB PDB - 8X64: CryoEM structure of the histamine H1 receptor-BRIL/Anti BRIL Fab complex with desloratadine (RCSB Protein Data Bank, 2026).
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Representative model, for educational purposes only.