Ternary complexation of carvedilol, -cyclodextrin and citric acid for mouth-dissolving tablet formulation

Accepted March 11, 2009 The purpose of this study was to improve the solubility and dissolution rate of carvedilol by forming a ternary complex with b-cyclodextrin and citric acid and to formulate its mouth-dissolving tablets. The rationale for preparing mouth-dissolving tablet of carvedilol was to make the drug available in a soluble form in the mouth, which would facilitate its absorption from the buccal cavity. This would help to overcome its first-pass metabolism and thereby improve bioavailability. Phase solubility studies revealed the ability of b-cyclodextrin and citric acid to complex with carvedilol and significantly increase its solubility. Ternary complexation of carvedilol was carried out with b-cyclodextrin and citric acid by physical mixing, kneading and spray drying methods and the prepared complexes were characterized by Fourier transform infra red spectroscopy, differential scanning calorimetry, powder X-ray diffractometry, scanning electron microscopy and complexation efficiency. The complex obtained by the spray drying method resulted in highest complexation efficiency and a 110-fold increase in the solubility of carvedilol. The mouth-dissolving tablets formulated using the spray dried complex with suitable excipients showed 100 % dissolution within five minutes. Accelerated stability studies of mouth-dissolving tablets carried out as per ICH guidelines revealed that the tablets were stable.