Co-amorphous drug systems of carbamazepine: intrinsic dissolution rate improvements

Co-amorphous systems is one of the attractive strategies used to enhance the dissolution rates of poorly soluble drugs. This strategy has an additional advantage as it has the ability to overcome stability issues that may arise from the conversion of a crystalline drug into its amorphous form. In this study, quench cooling was used to prepare co-amorphous forms of carbamazepine (CBZ) with saccharin (SAC), lactose (LAC) and gluconolactone (GLU) as carriers. Analytical techniques such as P-XRD, DSC and SEM were used to confirm the conversion to the amorphous state. In addition, the intrinsic dissolution rates (IDR) of the new drug forms were also investigated. Co-amorphous systems of CBZ as a parent drug with SAC, LAC and GLU were successfully formulated. CBZ-LAC had the highest IDR (0.339 mg/min/cm2) when compared to the untreated CBZ (0.091 mg/min/cm2). P-XRD and DSC showed CBZ-SAC and CBZ-LAC to be stable after storage at room temperature (22 ± 1 °C) for 30 days and relative humidity of 35–47 %. However, CBZ-GLU started to crystallize on storage and as such may require other excipients to stabilize its co-amorphous form.