KETOTIFEN

Zaditen,Wander,Switz.,1978

Anti-asthmatic.

Ketotifen is an intermediate in the synthesis of Ketotifen N-Oxide Hydrochloride (K315410), which is a metabolite of Ketotifen (K315100) in humans; formed by human liver microsome. For the free base, see K315115.

ChEBI: Ketotifen is an organic heterotricyclic compound that is 4,9-dihydro-10H-benzo[4,5]cyclohepta[1,2-b]thiophen-10-one which is substituted at position 4 by a 1-methylpiperidin-4-ylidene group. A blocker of histamine H1 receptors with a stabilising action on mast cells, it is used (usually as its hydrogen fumarate salt) for the treatment of asthma, where it may take several weeks to exert its full effect. It has a role as a H1-receptor antagonist and an anti-asthmatic drug. It is an organosulfur heterocyclic compound, an organic heterotricyclic compound, a cyclic ketone, a member of piperidines, an olefinic compound and a tertiary amino compound. It is a conjugate base of a ketotifen(1+).

3.07 g of iodine-activated magnesium shavings are covered with a layer of 25 cc of tetrahydrofuran, and approximately 1/10 of a solution of 17.7 g of 4- chloro-1-methylpiperidine base in 70 cc of absolute tetrahydrofuran is added. The Grignard reaction is initiated by the addition of a few drops of 1,2- dibromoethane. The remaining 4-chloro-1-methylpiperidine solution is then added dropwise to the magnesium at such a rate that the reaction mixture boils continuously at reflux without external heating. Boiling at reflux is then continued for 1 hour. 15.3 g of 10-methoxy-4H-benzo[4,5]cyclohepta[1,2- b]thiophen-4-one are subsequently added portionwise at 20°C, within 40 minutes, with slight cooling. After stirring at 20°C for 1,5 hours, the reaction solution is poured on a mixture of 180 g of ice and 20 g of ammonium chloride. The free base is extracted with chloroform.
The chloroform solution is concentrated and the residue recrystallized from 270 cc of absolute ethanol. The pure 10-methoxy-4-(1-methyl-4-piperidyl)- 4H-benzo[4,5]cyclohepta[1,2-b]thiophen-4-ol base, having a melting point of 194°C to 196°C, is obtained in this manner. Microanalysis corresponds with the formula C20H23NO2S.
A mixture of 3.4 g of 10-methoxy-4-(1-methyl-4-piperidyl)-4H-benzo[4,5] cyclohepta [1,2-b]thiophen-4-ol base and 40 cc of 3N hydrochloric acid is kept in a boiling water bath at 95°C to 100°C for 1 hour. The mixture is subsequently made alkaline with concentrated caustic soda solution at 20°C while cooling, and the free base is extracted with chloroform. The chloroform solution is concentrated, and the residue is recrystallized from ethanol/water 1:1. The pure 4-(1-methyl-4-piperidylidene)-4H-benzo[4,5]cyclohepta [1,2-b] thiophen-10(9H)-one base, having a melting point of 152°C to 153°C, is obtained in this manner.

Zaditor (Novartis).

Anti-asthmatic, Antihistaminic

Crystals (from ethyl acetate).

Flash point data for KETOTIFEN are not available. KETOTIFEN is probably combustible.

Ketotifen is a potent, selective H1 antihistamine that also prevents release of transmitters from mast cells. It is approved in the United States for topical use to prevent itching of the eye because of allergic conjunctivitis, It is used as a systemic antiallergy agent in several countries outside the United States for the treatment of seasonal allergic rhinitis, hay fever, and asthma. Being structurally analogous to the cyproheptadine-like antihistamines, differences in activity of the two enantiomers (atropisomers) has been noted, being approximately six- to seven-fold in ligand displacement and rodent-based assays. Ketotifen has been shown to stabilize mast cells and to inhibit degranulation of eosinophils. Like olopatadine, it has been shown to interact with model membranes, stabilizing them by interaction with phospholipids monolayers.