Application of simplex lattice design for the development of extended release tablets of model drug diclofenac sodium.

Aim: Simplex lattice design was applied to predict extent of drug release from extended release diclofenac sodium tablets. Methods: The effects of composition on dissolution rate were evaluated by varying the levels of hydroxypropyl methylcellulose, dicalcium phosphate and cornstarch via three component design. Results: The rate of drug release was primarily dictated by the proportion of hydroxypropyl methylcellulose and was also affected by the proportion of dicalcium phosphate and the method of processing (direct compression/wet granulation). Polynomial equations constructed for directly compressed and wet-granulated formulations could successfully predict the extent of drug release at an arbitrary time point of 3 h. Conclusion: Simplex lattice design is a viable tool to predict the drug release patterns of extended release formulations.

Effect of the Interaction Between an Ionic Surfactant and Polymer on the Dissolution of a Poorly Soluble Drug.

Surfactants are commonly incorporated in conventional and enabled formulations to enhance the rate and extent of dissolution of drugs exhibiting poor aqueous solubility. Generally the interactions between the drug and excipients are systematically evaluated, however, limited attention is paid towards understanding the effect of interaction between functional excipients and its impact on the performance of the product. In the current study, the effect of potential interaction between a nonionic polymer binder, povidone, and anionic surfactant docusate sodium on the rate and extent of dissolution of a drug exhibiting poor aqueous solubility was evaluated by varying the proportions of the binder and the surfactant in the formulation. Potential complexation or aggregation between the excipients was investigated by fluorescence spectroscopy and zeta potential measurements of the aqueous solutions of docusate sodium, povidone, and sodium lauryl sulfate (SLS). The rate and extent of drug release was found to decrease with an increase in the proportion of docusate sodium and povidone in the formulations. Difference in magnitude of surface charge (zeta potential) of docusate sodium in presence of povidone indicated potential surfactant-polymer aggregation during dissolution which was corroborated by CAC/CMC values derived from fluorescence spectroscopic measurements. The decrease in the rate of drug release was attributed to an increase in the viscosity of the microenvironment of dissolving particles due to the interaction of docusate sodium and povidone in the aqueous media during dissolution. These findings highlight the importance of systematic evaluation of the interaction of ionic surfactants with the polymeric components within the formulation to ensure the appropriate selection of the type of surfactant as well as its proportion in the formulation.