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