Ketotifen in the management of chronic urticaria: resurrection of an old drug.

Ketotifen is an oral antiallergic drug developed in 1970 by Sandoz Pharmaceuticals of Switzerland. It is a benzocycloheptathiophene derivative and was initially marketed as an inhibitor of anaphylaxis.1 The pharmacodynamic properties of ketotifen are many, because it is an inhibitor of the release and/or activity of mast cell and basophil mediators, including histamine, neutrophil, and eosinophil chemotactic factors, arachidonic acid metabolites, prostaglandins, and leukotrienes.2 Thus, it inhibits the bronchial response to inhaled histamine, allergen, or aspirin. In addition, the ocular, nasal, and dermal responses to applied allergen in sensitized patients are attenuated with use of ketotifen.3 It also has been found to have some calcium antagonist activity and to inhibit responses to platelet-activating factor from proinflammatory cells, such as eosinophils.2 Additional possible modes of action include its ability to reverse b2-agonisteinduced decreases in b-adrenoreceptor density and to alter the affinity of these receptors and increase intracellular concentrations of cyclic adenosine monophosphate.3 Ketotifen has a chemical structure similar to some first-generation antihistamines, such as cyproheptadine and azatidene.2 With regard to the pharmacokinetic properties of ketotifen, it is readily absorbed from the gastrointestinal tract after oral administration and achieves peak plasma concentrations within 2 to 4 hours of administration. Clearance of the drug from plasma is biphasic, with a half-life of distribution of 3 hours and a half-life of elimination of 22 hours in adults.3 However, the onset of action of ketotifen is slow, and it may take 4 to 6 weeks to achieve full prophylactic value under certain conditions.4 Ketotifen was originally patented by Sandoz in the 1970s. It became very popular for management of asthma in Japan and clinical trials were initiated in the United States in the 1980s for management of asthma and other allergic conditions. One author served on the Food and Drug Administration (FDA) Pulmonarye Allergy Drugs Advisory Committee and chaired that group from 1984 to 1986. Approval for treatment of asthma was not granted, but FDA staff did recommend more extensive evaluations for management of urticaria. Unfortunately, the latter studies have not been performed in a robust fashion. However, oral ketotifen has been used in patients with asthma, allergic rhinitis, allergic conjunctivitis, atopic dermatitis, chronic urticaria, cold-induced urticaria, cholinergic urticaria, exercise-induced urticaria, mastocytosis, and food allergy in Canada, Europe, and Mexico. Approval was granted for ocular administration in the United States for allergic conjunctivitis and later the drug became available over the counter. A review of clintrials.gov shows evaluations of ketotifen by oral administration for fibromyalgia, atopic dermatitis, attenuation of reactions during peanut desensitization, allergic rhinitis, asthma, and post-traumatic joint contractures. The authors became aware that ketotifen could be obtained in the United States from compounding pharmacies and began prescribing it more extensively in their clinics for severe urticaria in 2011. For adults and older children with asthma or allergic disease, the recommended dose of ketotifen is 1 mg twice daily. For young children 6 months to 3 years old, the recommended dose is 0.5 mg twice daily.3 It must be noted that oral ketotifen can be safely compounded in the United States. Pharmacy compounding is a practice in which a licensed pharmacist combines, mixes, or alters ingredients in response to a prescription to create a medication tailored to the medical needs of an individual patient. Pharmacy compounding, if performed properly, can serve an important public health need if a patient cannot be treated with an FDA-approved medication. The issue of safety of compounded drugs in the FDA Compliance Policy for Pharmacy Compounding is primarily for injectable drugs and does not relate to oral compounded drugs. This policy does include a select list of compounding drugs that were withdrawn or Reprints: Kristin C. Sokol, MD, MS, MPH, Division of Allergy and Immunology, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555; E-mail: [email protected]. Disclosures: Authors have nothing to disclose. Funding Sources: This study was conducted with the support of the Institute for Translational Sciences at the University of Texas Medical Branch, supported in part by a Clinical and Translational Science Award (UL1TR000071) from the National Center for Advancing Translational Sciences, National Institutes of Health.