Dilute solution properties of clindamycin 2-palmitate hydrochloride

Clindamycin 2-palmitate hydrochloride forms micelles in aqueous solution at concentrations above 2-2 X 10(-3) M. Dilution of micellar solutions of the drug to concentrations less than 2-0 X 10(-3) M produces turbid systems. Turbidity is caused by unionized drug, produced by hydrolysis of the salt, phasing out of solution at concentrations too low for micelles to be formed. Changes in specific conductivity and turbidity associated with the phasing-out process have been measured and explained in terms of the rates of the various processes involved, including demicellization and emulsion stability. The phenomenon of phasing-out, below a critical concentration in aqueous solution, is predicted to be a general one for weakly ionized surfactants where the unionized species possesses low water solubility.