Ketotifen is an oral antihistamine and mast-cell stabilizer. The active ingredient in these capsules is ketotifen (as ketotifen fumarate).
It belongs to the same drug family as the ketotifen eye drops sold over the counter for itchy eyes, but here it is taken by mouth to act throughout the body.
How does it work?
As an H1-antihistamine, ketotifen blocks the H1 histamine receptor so histamine has less effect on tissues; as a mast-cell stabilizer, it makes mast cells less likely to release histamine and other inflammatory mediators. Antihistamines in this class are used to blunt histamine-driven symptoms such as itching and hives (StatPearls: Antihistamines).
What is it used for?
Providers may prescribe oral ketotifen off-label for mast cell activation syndrome (MCAS), chronic urticaria (hives), and other allergic or histamine-related conditions. Whether it is a reasonable option, and for which symptoms, is a decision your provider makes for your situation.
Oral ketotifen vs. the eye drops
In the United States, the only ketotifen product sold commercially is the over-the-counter ophthalmic (eye drop) form, applied to the eyes for allergy itching (MedlinePlus: ketotifen ophthalmic). An oral capsule is different: it is taken by mouth to reach the whole body rather than treating the surface of the eye, and because no manufactured oral product exists in the US, it is compounded.
How is it used?
Oral ketotifen is taken by mouth as a capsule. Your provider sets the strength, how many times a day, and the schedule; because sedation is common early on, it is sometimes started low and taken in the evening.
Side effects & safety
The most common effect is drowsiness or sedation, which is often strongest in the first days to weeks and may ease with time. Other reported effects include dry mouth, increased appetite and weight gain, and dizziness. Ketotifen can add to the sedating effects of alcohol and other sedating medicines, so use caution driving or operating machinery until you know how it affects you (StatPearls: Antihistamines).
Who should not use it?
Ketotifen may not be suitable for everyone. Tell your provider about your full medical history and all medicines you take, including alcohol and other sedatives. Extra caution is advised in children and older adults, and if you are pregnant or breastfeeding, discuss it with your provider (LactMed: Ketotifen).
How should it be stored?
Store the capsules as directed on your prescription label, at room temperature and away from excess heat and moisture, and keep them out of reach of children and pets.
Why is this compounded?
Because an oral form of ketotifen is not manufactured or FDA-approved in the United States, Bayview Pharmacy compounds the capsules to the strength your provider prescribes, prepared in small batches under USP <795>.
Clinical details for prescribers
Regulatory status. Ketotifen is not a controlled substance. Only ophthalmic ketotifen is FDA-approved in the United States; oral ketotifen is available only as a compounded medication and its uses (mast cell activation, chronic urticaria, allergic conditions) are off-label.
Formulation & dosing. Compounded as 0.5, 1, and 2 mg oral capsules. Commonly reported dosing is 1 mg twice daily; many prescribers start at 0.5 mg at bedtime and titrate over 1–2 weeks to limit sedation, with some regimens advancing to 2 mg twice daily.
Counseling / clinical points:
- Drowsiness is the most common early effect and typically wanes within 1–2 weeks — bedtime-weighted titration helps
- Additive sedation with alcohol and other CNS depressants
- Appetite stimulation and weight gain are possible with ongoing use
- Benefit accrues over weeks; counsel patients not to judge response too early
Ketotifen combines H1 antihistamine activity with mast-cell stabilization, which is why it is often chosen over standard antihistamines in mast-cell-driven conditions.
Ketotifen Capsules is a compounded medication and is not FDA-approved. This information is educational and is not medical advice. Your provider determines whether it is appropriate and sets the dose.
