The Process Of Manufaturing Pharmaceutical Grade Tannates

Abstract: Antihistamines are available in the from of free bases as well as salts i. e. hydrochloride, maleate, tannate ect.Frequently, it is necessary to utilise antihistamines in the from of tannate salt because such salts are generally quite stable and may be administered in such from without untoward side effects. Tannic acid, also known as tannin, is a well known naturally occurring substance. Tannic acid, which is availble commercially usually cvontain about 5% of water has a molecualr weight of about 1700 and is typically produced from Turkish or Chinese nutgall. Antihistamine tannates presently manufactured commercially, are relatively impure Such tannates are prepared by the reaction of antihistamine free base with tannic acid and using a volatile solvent, isopropanol (IPA). The yield is only fair (around 70%) and decomposition products e.g 2-5% along with significant amount of volatile, isopropanol (6-10%) remains with the product, which cannot be removed. According to present invention, for specific types of tannates, isopropanol (IPA) is removed by adding water while stirring and dispersing the wet cake of tannate, IT is then filtered and the tannate residue is dried to obtain pharmaceutical grade tannate. Tannates like chlorpheniramine tannate and pyrilamine tannates have been prepared by this method

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