Benzatropine mesilate

In some cases hydrochloride salts are not very water soluble due to the strength of association between the base and its counter ion, and other salts have to be used. For instance, salts may be prepared with di- or tricarboxylic acids, e.g. ergometrine tartrate, diethylcarbamazine citrate, sumatriptan succinate (Fig. 3.18) and lisuride maleate are all used because of the water insolubility of their hydrochlorides. Similarly strong monobasic organic acids such as mesilate are used to promote water solubility, as in the case of benzatropine mesilate (Fig. 3.18) andphentol-amine mesilate. In some instmces salts are too ready to absorb water from the atmosphere, for instance the muscle relaxant dmg atracurium is formulated as its besilate salt to avoid the problems of water absorption experienced with its mesilate. 

Benztropine has similar uses and administration to benzhexol. It shares the tropine ring with atropine hut the ester is replaced with an ether and branched benzyl groups. It has some antihistamine and local anaesthetic activity but is not indicated for such uses. Benzatropine (used as the mesilate salt) has a longer half-life than benzhexol and is used as a single daily dose (1-6 mg). It is available in oral (tablet) or injectable (i.m.) dosage forms. 

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