Investigation of solubility and dissolution of a free base and two different salt forms as a function of pH.

Purpose: To evaluate the effect of pH on solubility and dissolution rates of a model weak base, haloperidol, and two different salt forms, hydrochloride and mesylate.

Methods: pH-solubility profiles were determined by using haloperidol base, haloperidol hydrochloride, and haloperidol mesylate as starting materials; concentrated or diluted HCl or NaOH solutions were added to aqueous suspensions of solids to adjust pH to desired values. Intrinsic dissolution rates were determined using intrinsic dissolution apparatus under various pH-stat conditions.