Ketotifen, sold under the brand name Zaditor among others, is a second-generation noncompetitive H₁-

antihistamine Antihistamines are drugs which treat allergic rhinitis, common cold, influenza, and other allergies. Typically, people take antihistamines as an inexpensive, generic (not patented) drug that can be bought without a prescription and provide ...

and

mast cell stabilizer Mast cell stabilizers are medications used to prevent or control certain allergic disorders. They block mast cell degranulation, stabilizing the cell and thereby preventing the release of histamine and related mediators. One suspected pharmaco ...

. It is most commonly sold as a

salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quant ...

with

fumaric acid Fumaric acid is an organic compound with the formula HO2CCH=CHCO2H. A white solid, fumaric acid occurs widely in nature. It has a fruit-like taste and has been used as a food additive. Its E number is E297. The salts and esters are known as fu ...

, ketotifen fumarate, and is available in two forms. In its ophthalmic form, it is used to treat

allergic conjunctivitis Allergic conjunctivitis (AC) is inflammation of the conjunctiva (the membrane covering the white part of the eye) due to allergy. Although allergens differ among patients, the most common cause is hay fever. Symptoms consist of redness (mainly due ...

. In its

oral The word oral may refer to: Relating to the mouth * Relating to the mouth, the first portion of the alimentary canal that primarily receives food and liquid ** Oral administration of medicines ** Oral examination (also known as an oral exam or or ...

form, it is used to prevent

asthma Asthma is a long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and easily triggered bronchospasms. Symptoms include episodes of wheezing, co ...

attacks or anaphylaxis, as well as various mast cell, allergic-type disorders. It was patented in 1970 and came into medical use in 1976. In 2020, it was the 289th most commonly prescribed medication in the United States, with more than 1million prescriptions.

Medical uses

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 Leukotrienes are a family of eicosanoid inflammatory mediators produced in leukocytes by the oxidation of arachidonic acid (AA) and the essential fatty acid eicosapentaenoic acid (EPA) by the enzyme arachidonate 5-lipoxygenase. Leukotrienes ...

antagonist and a

phosphodiesterase inhibitor A phosphodiesterase inhibitor is a drug that blocks one or more of the five subtypes of the enzyme phosphodiesterase (PDE), thereby preventing the inactivation of the intracellular second messengers, cyclic adenosine monophosphate (cAMP) and c ...

. " al ketotifen has been used in patients with asthma, allergic rhinitis, allergic conjunctivitis, atopic dermatitis, chronic urticaria, cold-induced urticaria, cholinergic urticaria, exercise-induced urticaria, ystemic mast cell disease including mastocytosis, Mast Cell Activation Syndrome (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." The drug may also help relieve

irritable bowel syndrome Irritable bowel syndrome (IBS) is a "disorder of gut-brain interaction" characterized by a group of symptoms that commonly include abdominal pain and or abdominal bloating and changes in the consistency of bowel movements. These symptoms may ...

Side effects

Side effects of systemic (oral) use include drowsiness, weight gain (11-12lbs), dry mouth, irritability, and increased nosebleeds.

Pharmacology

Ketotifen is a selective

– that is, an

inverse agonist In pharmacology, an inverse agonist is a drug that binds to the same receptor as an agonist but induces a pharmacological response opposite to that of the agonist. A neutral antagonist has no activity in the absence of an agonist or inverse ago ...

of the

histamine Histamine is an organic nitrogenous compound involved in local immune responses, as well as regulating physiological functions in the gut and acting as a neurotransmitter for the brain, spinal cord, and uterus. Since histamine was discover ...

H₁ receptor (K_i = 0.166 nM) – and

. In addition, ketotifen has weak

anticholinergic Anticholinergics (anticholinergic agents) are substances that block the action of the neurotransmitter called acetylcholine (ACh) at synapses in the central and peripheral nervous system. These agents inhibit the parasympathetic nervous sys ...

(K_i = 204 nM for ) and

antiserotonergic A serotonin antagonist, or serotonin receptor antagonist, is a drug used to inhibit the action at serotonin (5-HT) receptors. Types 5-HT2A antagonists Antagonists of the 5-HT2A receptor are sometimes used as atypical antipsychotics (contrast wi ...

(K_i = 38.9 nM for 5-HT_2A) 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

Brand names

Ketotifen is marketed under many brand names worldwide.

References

External links

* {{Portal bar , Medicine Benzocycloheptathiophenes H1 receptor antagonists Mast cell stabilizers Novartis brands Piperidines Serotonin receptor antagonists