[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [Ophthalmic antiallergics](https://durgical.com/en/pharmacology/classes/ophthalmic-antiallergics/) › Ketotifen

# Ketotifen

## Ophthalmic antiallergics?

Ophthalmic antiallergics

An antihistamine eye drop that also steadies mast cells. It relieves the itch of allergic conjunctivitis for several hours.

Updated Nov 1, 2026

## Quick facts

**Group**
[Ophthalmic antiallergics](https://durgical.com/en/pharmacology/classes/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.

On this page

- The basics Mechanism of action
- Indications
- Adverse effects
- Pharmacokinetics
- Memory aid

- Safety Contraindications
- Key interactions
- What is monitored
- Administration and safety
- Pregnancy and breastfeeding
- Nursing care

- Study Test yourself

- Connections Connections

## Mechanism of action

◎**Histamine H1 receptor (plus mast cell stabilisation)**Ketotifen

ⓘ The figure shows desloratadine, another H1 antihistamine, in the human H1 receptor; ketotifen blocks the same receptor.

**Target in 3D:** Histamine H1 receptor (plus mast cell stabilisation). PDB structure 8X64 (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/8X64) · Drag to rotate · pinch to zoom

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 →](https://durgical.com/en/conditions/conjunctivitis/)

## Adverse effects

### Common

- Burning or stinging of the eye
- Headache, runny nose
- Dry eye, eye discharge, light sensitivity
- Blurred vision

### Serious (rare, important)

- Eye pain or vision change (may not be allergy)
- Itching that worsens or lasts beyond a few days

## 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

## Memory aid

«Keto calms the itch»: H1 block plus mast cell calm, from one drop.

## 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.

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/pharmacology/ketotifen/)

[More Pharmacology questions →](https://durgical.com/en/practice/?f=pharmacology)

## Connections

## Related drugs 2

- [Olopatadine](https://durgical.com/en/pharmacology/olopatadine/)
- [Cromoglicic acid](https://durgical.com/en/pharmacology/cromoglicic-acid/)

## Related conditions 1

- [Conjunctivitis](https://durgical.com/en/conditions/conjunctivitis/)

[← Back to the class: Ophthalmic antiallergics](https://durgical.com/en/pharmacology/classes/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](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=7e7be193-63ec-474d-a596-e22fc8b1be0f) (DailyMed (U.S. National Library of Medicine), 2026); [Ketotifen Ophthalmic: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a604033.html) (MedlinePlus (U.S. National Library of Medicine), 2026); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=S01GX08) (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](https://www.rcsb.org/structure/8X64) (RCSB Protein Data Bank, 2026).

## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake

Representative model, for educational purposes only.

---
Source: https://durgical.com/en/pharmacology/ketotifen/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/ketotifen/