Piperazines derivatives

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Chapter: Medicinal Chemistry : Antihistamines

Antihistamines : H1-antagonists with classical structure :Piperazines derivatives - Synthesis and Drug Profile - i. Cyclizine (Marezine) ii. Chlorcyclizine (Diparalene) iii. Meclizine (Antivert, Bonine)


SYNTHESIS AND DRUG PROFILE

 

H1-antagonists with classical structure

 

Piperazines derivatives

 

i. Cyclizine (Marezine)


Synthesis


Properties and uses: Cyclizine hydrochloride is a white crystalline powder, slightly soluble in water and in alcohol. It is mostly employed as a prophylaxis and for the treatment of motion sickness.

Assay: Dissolve the sample in anhydrous formic acid, add acetic anhydride and titrates against 0.1 M perchloric acid. Determine the end point potentiometrically.

Dose: Usual dose is 25–100 mg per day.

Dosage forms: Cyclizine HCl tablets I.P., Cyclizine injection B.P., Cyclizine tablets B.P., Dipipanone and cyclizine tablets B.P.

 

ii. Chlorcyclizine (Diparalene)


Synthesis


Properties and uses: Chlorcyclizine hydrochloride is a white crystalline powder, soluble in water, methylene chloride and in alcohol. Substitution of halogen in the 2nd or 3rd position of either of the benzhydryl rings results in a much less potent activity. Chlorcyclizine is indicated in the symptomatic relief of utricaria, hay fever, and certain other allergic conditions.

Assay: Dissolve the sample in a mixture of 0.1 M hydrochloric acid and methanol and titrate against 0.1 M sodium hydroxide. Determine end point potentiometrically.

Dose: Usual dose is 50–200 mg per day.

 

iii. Meclizine (Antivert, Bonine)


Synthesis


Properties and uses: It is a white or slightly yellowish, crystalline powder with no characteristic odour and taste. It is insoluble in water and in ether, but soluble in chloroform and alcohol. It is a moderately potent antihistaminic agent. It is used primarily as an antinauseant in the prevention and treatment of motion sickness; in the treatment of nausea and vomiting associated with vertigo and radiation sickness.

Assay: Dissolve the sample in alcohol and titrate against 0.1 M sodium hydroxide. Determine the end point potentiometrically.

Dose: Usual dose is 25–50 mg per day.

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