Products
Ketotifen is commercially available in tablet form and as eye drops (Zaditen, Zabak). It has been approved in many countries since 1977. See also under ketotifen eye drops.
Structure and properties
Ketotifen (C19H19NOS, Mr = 309.43 g/mol) is a tricyclic benzocycloheptathiophene derivative structurally related to pizotifen (Mosegor, out of commerce). It is present in drugs as ketotifen hydrogen fumarate, a white to brownish yellow crystalline powder that is sparingly soluble in water.
Effects
Ketotifen (ATC R06AX17) has antihistamine, antiallergic, antiinflammatory, and mild anticholinergic properties. It is an antihistamine and additionally inhibits the release of inflammatory mediators such as histamine and the leukotrienes.
Indications
- Chronic idiopathic urticaria (e.g., cold urticaria).
- Allergic rhinitis
- Allergic conjunctivitis
- Atopic dermatitis
- For the prevention of asthmatic symptoms (not in many countries).
Ketotifen can potentially be used for loss of appetite, as Pizotifen (Mosegor) was, because it promotes appetite, but it is not approved for this purpose and has been insufficiently studied.
Dosage
According to the SmPC. Tablets are taken with meals. It should be noted that the full effect of oral administration occurs only after several weeks. In contrast, when applied topically to the eye, the antihistamine effects are immediate.
Contraindications
- Hypersensitivity
- Epilepsy
- Seizures in the patient history
- Breastfeeding
Full precautions can be found in the drug label.
Interactions
Centrally acting agents such as alcohol, sedatives, antidepressants, antihistamines, and sleeping pills may increase adverse effects. A decrease in platelets has rarely been reported with concomitant administration of oral antidiabetic agents. Ketotifen may potentiate the effects of bronchodilators.
Adverse Effects
Possible adverse effects include agitation, irritability, insomnia, nervousness, dizziness, fatigue, dry mouth, weight gain, skin disorders, and infectious diseases. The eye drops may cause local reactions such as a burning and stinging sensation. Systemic side effects, on the other hand, are rarely observed with topical use.
