Effect of enantiomeric purity on solubility determination of dexclamol hydrochloride.

The solubility of (+/-)-4a,13b-trans)-[3(OH),13b(H)-trans]-3-isopropyl - 2,3,4,4a,8,9,13b,14- octahydro-1H - benzo[6,7]cycloheptal[1,2,3-de]pyrido[2,1-a]isoquinolin-3-ol hydrochloride [(+/-)-I] was 3.3 mg/ml in pure water. Its resolved enantiomers exhibited about a fivefold increase in solubility. Dexclamol hydrochloride, the (+)-I enantiomer, is bioactive as a neuroleptic and is soluble to the extent of 16.4 mg/ml. However, raw material purity in relation to the amounts of (+/-)-I racemate present significantly influences solubility and optimum conditions for dissolution. The effect of trace amounts of (-)-I or (+/-)-I forms of the solubility of (+)-I enantiomer raw materials was explained through phase solubility studies. Conditions required for preparation of clear solutions using raw materials of varying purity can be determined with derived expressions. The application and limitations of using an enantiomer as a tool to improve solubility are discussed.