Understanding impact of pre-dissolved polymers on dissolution behavior of soluble carbamazepine cocrystal

Cocrystallization is a novel approach for tackling the lower solubility concerns when they can yield solution concentration a lot better than their corresponding parent drug in crystalline form. To get the actual solubility and dissolution gains offered by the cocrystals, phase changes in solution (dissolution) has to be interrupted. In current study, we selected commonly used polymers in order to study their effects on the super saturation of carbamezepine-succinic acid (CBZ-SUC) cocrystal during dissolution studies. To observe solid phase changes during dissolution in situ Raman spectroscopy was used. At the completion of each test the solid phase was analyzed by Fourier-transform infrared spectroscopy (FTIR) and powder X-Ray diffractometry. In polymers absence, no dissolution improvement was achieved by the cocrystal owing to its quick transformation to the stable carbamazepine dihydrate (CBZDH). Pre-dissolved PVP at 2% w/v concentration did not inhibit CBZ crystallization as a dihydrate, whereas at 0.025% w/v pre-dissolved hydroxypropyl methyl cellulose acetate succinate (HPMCAS) did stabilize the cocrystal in buffer solution (pH 6.8) for the course of time studied. This cocrystal stabilization resulted in enhanced CBZ solubility ( ̴ 4fold) caused by cocrystal super saturation state. Seeding of this stable supersaturated state with 1% w/v CBZDH resulted in CBZ crystallization as dihydrate with ultimate loss of solubility advantage.