Parenteral formulation of the kappa agonist analgesic, DuP 747, via micellar solubilization.

The nonopioid kappa agonist analgesic amine, DuP 747, as a hydrochloride salt exhibited an aqueous solubility of 3 mg/ml. This solubility was insufficient to provide the desired dose in a solution formulation for intramuscular administration. Aqueous solutions of the hydrochloride salt exerted surface activity behavior; however, the critical micellar concentration (CMC) was not reached at the saturation solubility. Enhanced aqueous solubility required to reach the CMC could lead to micellization of the compound and a possible i.m. solution formula. The methanesulfonate salt was more water soluble than the hydrochloride salt and yielded a micellar solution with a concentration of 60 mg/ml.