Influence of additives on the clouding phenomenon of chlorpromazine hydrochloride solutions

Herein we report the effect of various additives (viz. alcohols, cycloalcohols, amino acids, sugars, ureas) on the clouding phenomenon observed in 50 mM chlorpromazine hydrochloride (CPZ) drug solutions (prepared in 10 mM sodium phosphate buffer). Long chain alcohols (except octanol), cyclohexanol and allylalcohol increased the cloud point (CP) followed by a decrease with the increase in alcohol concentration but short chain alcohols affected the CP insignificantly. Effect of amino acids depended upon their nature: acidic and salts of basic amino acids increased the CP while basic amino acids depressed it; non-polar and uncharged polar amino acids caused small changes in CP. Additives of urea family decreased the CP. All sugars caused a decrease in CP, which is in consonance to their effect on the critical micellar concentration. The overall behavior is explained on the basis of additives affecting the solvent as well as micelle aggregation and/or structure.