Products
Clemastine is commercially available in tablet form and as a solution for injection (Tavegyl). It has been approved in many countries since 1967. Tavegyl gel has been off the market since 2010 because of low demand. It can be replaced, for example, by a dimetindene maleate gel (Fenistil).
Structure and properties
Clemastine (C21H26ClNO, Mr = 343.9 g/mol) is present in drugs as -lemastine fumarate, a white crystalline powder that is very sparingly soluble in water. It is a methylpyrrolidine derivative and belongs to the benzhydryl ether group.
Effects
Clemastine (ATC R06AA14) has antihistamine and antiallergic properties. The effects are due to antagonism at histamine H1 receptors. Compared with modern 2nd generation antihistamines, clemastine is more depressant (sedative) and anticholinergic. It has a duration of action of 10-12 hours and must be administered twice daily.
Indications
- Hay fever
- Allergic rhinitis
- Hives, dermographism
- Itching
- Itchy skin diseases
- Acute and chronic eczema, contact dermatitis, drug exanthema (adjunctive therapy).
- Insect bites and stings
Dosage
According to the package leaflet. The tablets are usually taken in the morning and evening before meals.
Contraindications
- Hypersensitivity
- Porphyria
Full precautions can be found in the drug label.
Interactions
Drug-drug interactions are possible with centrally depressant drugs. According to the German SmPC, CYP inhibitors such as azole antifungals should not be administered concomitantly.
Adverse effects
The most common adverse effects include fatigue, dullness, dizziness, headache, stomach pain, nausea, dry mouth, and constipation. In children, paradoxical states of agitation may occur, and rapid heartbeat is rarely observed.