Drug release characteristics from nanoclay hybrids and their dispersions in organic polymers

This study establishes and compares structure-property-processing relationships on three drug delivery systems containing an anionic active pharmaceutical ingredient (API) in the following excipient carriers: (a) an inorganic anionic nanoclay, (b) pH responsive acrylic polymers, and (c) combinations thereof. The effects of the excipients on the APIs dissolution rate were studied from their release profile in simulated body fluids (SBFs) with different pH. In the API-nanoclay system, calcination of the clay followed by its reconstitution in an API solution was successfully used to intercalate the API in its amorphous state in the clay. As a result, the API showed increased apparent solubility vs. its crystalline form with its release mechanism from the clay being predominantly diffusion controlled and depending on the pH of the SBFs. In melt mixed ternary polymer systems containing the above hybrids, as a result of an additional diffusional step due to presence of nanoplatelets, the API showed a more controlled release vs. polymer systems that contained only API. By comparison to the low pH SBF, the ternary system in the pH 7.4 SBF showed a reduced diffusion contribution due to the presence of clay platelets, the latter unaffected by the high pH value. Reasonable agreement was found with predictions from literature diffusion/erosion models. It is confirmed that hot melt mixing offers opportunities to produce systems with enhanced API apparent solubility. The presence of nanoclays can also increase the API's apparent solubility and affect its release in a controlled manner.