Effect of solvent type on retardation properties of diltiazem HCl form liquisolid tablets.

Liquisolid technique is a new approach to formulate sustained release dosage forms. It seems that the solubility of an active ingredient in solvent plays an important role in drug release profile. The aim of present study was to investigate the effect of solvent type on diltiazem hydrochloride release profile from liquisolid compacts. To examine aforementioned idea, the drug solubility was studied in several conventional nonvolatile solvents. Liquisolid formulations of diltiazem HCl in the different solvents were prepared and their release profiles were also obtained. Effect of aging on the hardness and drug release profile was studied as well. X-ray crystallography and differential scanning calorimetry (DSC) were used to investigate the formation of any complex between drug and carrier or any crystallinity changes during the manufacturing process. The results showed that diltiazem HCl had lowest solubility in polysorbate 20. Highest amount was devoted to polysorbate 80 and propylene glycol. Type of nonvolatile solvent and its physicochemical properties as well as solubility of the drug in the applied solvent found to have important role on release profile of the drug from liquisolid compacts. Hardness and dissolution profile of the drug were not affected by aging. Amorphous form was obtained during the process of liquisolid formulation. It follows that the optimized new technique can be used to prepare sustained release formulations of water-soluble drugs.