Ketotifen

General information

Ketotifen was originally developed as a drug that would inhibit the release of vasoactive substances from mast cells, as an oral alternative to cromoglicate, but its actions in asthma are probably attributable to its antihistaminic effect [ , ], which occurs within minutes after administration and lasts for up to 12 hours. It also stabilizes mast cells, preventing histamine release, inhibits eosinophil accumulation in the lungs of animals exposed to platelet-activating factor, and reverses beta-adrenoceptor tachyphylaxis [ ]. It is classified as an antiallergic drug and is used as a prophylactic medicine.

Some trials have suggested that ketotifen has similar efficacy to cromoglicate in asthma [ ] and also a small steroid-sparing effect [ ]. It is more effective than placebo in the treatment of atopic dermatitis [ ].

Conjunctival injection, headache, and rhinitis are common. Allergic reactions, stinging, discharge, eye pain, and photophobia occurred in less than 5% of patients. The most common adverse reactions in long-term clinical trials were sedation and weight gain [ ].

In young children (with an average age 16 months) effective doses of ketotifen produced adverse reactions similar to those seen in adults, including dry mouth (28%) and sometimes increased appetite [ ]. In a series of 257 older children, increased weight was reported in 17, sedation in 13, and nausea in 3 [ ]. An evaluation of postmarketing surveillance of ketotifen in the UK showed, however, that the percentage of adverse effects reported in children was rather lower than in adults, sedation occurring in only 6% at the beginning of treatment. The corresponding figure in adults was 14% [ ].

Organs and systems