Introduction
Clemastine fumarate is a white crystalline powder, very slightly soluble in water slightly soluble in alcohol, and methanol. It has two chiral centers, each of which is (R) absolute configuration. A comparison of the activities of the antipodes indicates that the asymmetric center close to the side chain of nitrogen is of lesser importance to antihistaminic activity. It is a long-acting ethanolamine antihistamine with sedative and anticholinergic side effects.
Structure
Synthesis
Mechanism of Action:
Clemastine selectively antagonizes the histamine H1 receptor, inhibiting the action of endogenous histamine. This inhibition results in temporary relief from the negative symptoms induced by histamine.
Properties and uses:
- Commonly used to treat symptoms of allergic conditions, including allergic rhinitis (hay fever), hives (urticaria), and itching.
- It may be found in over-the-counter allergy medications and cough and cold preparations.
Assay:
Dissolve the sample in anhydrous acetic acid and titrate against 0.1 M perchloric acid. Determine the end-point potentiometrically.
Dosage forms:
Clemastine oral solution B.P., Clemastine tablets B.P.