|Trade names||Zaditor, Zaditen|
|Other names||Ketotifen fumarate|
|Drug class||H1-antihistamine, mast cell stabilizer|
|Main uses||Allergic conjunctivitis, allergic rhinitis|
|Side effects||By mouth: Anxiety, trouble sleeping, irritability|
Eye drops: Red eyes, runny nose, headache
|By mouth (tablets), topical eye drops|
|Elimination half-life||12 hours|
|Chemical and physical data|
|Molar mass||309.43 g·mol−1|
|3D model (JSmol)|
Common side effects, when taken by mouth, include anxiety, trouble sleeping, and irritability. Common side effects, when used as eye drops, include redness of the eyes, runny nose, and headache. While use is often not recommended, there is no evidence of harm in early pregnancy. It is a H1-antihistamine and mast cell stabilizer.
Ketotifen was patented in 1970 and came into medical use in 1976. In the United Kingdom 60 pills of 1 mg costs the NHS about £8. In the United States a 5 ml bottle of eye drops costs about 7 USD.
Ketotifen relieves and prevents eye itchiness and/or irritation associated with most seasonal allergies. It starts working within minutes after administering the drops. The drug has not been studied in children under three. The mean elimination half life is 12 hours. Besides its anti-histaminic activity, it is also a functional leukotriene antagonist and a phosphodiesterase inhibitor.
"[O]ral ketotifen has been used in patients with asthma, allergic rhinitis, allergic conjunctivitis, atopic dermatitis, chronic urticaria, cold-induced urticaria, cholinergic urticaria, exercise-induced urticaria, [systemic mast cell disease including mastocytosis, MCAS, allergic and nonallergic anaphylaxis, angioedema], and food allergy in Canada, Europe, and Mexico." Now available via prescription at US compounding pharmacies: "For adults and older children with asthma or allergic disease, the recommended dose of ketotifen is 1 mg twice daily." "FDA staff did recommend more extensive evaluations for management of urticaria."
It may be used at a dose of 0.5 mg once per day to 1 mg twice per day.
Side effects include drowsiness, weight gain (11-12lbs), dry mouth, irritability, and increased nosebleeds.
Ketotifen is a selective antihistamine – that is, an inverse agonist of the histamine H1 receptor (Ki = 0.166 nM) – and mast cell stabilizer. In addition, ketotifen has weak anticholinergic (Ki = 204 nM for mACh) and antiserotonergic (Ki = 38.9 nM for 5-HT2A) activity. However, at the dosages in which it is typically used clinically, both the anticholinergic and antiserotonergic activity of ketotifen are said not to be appreciable.
Society and culture
Ketotifen is marketed under many brand names worldwide.
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