Modelling structure of controlled-release drug based on polyurethane resin from castor oil plants through the pair distribution function (PDF) method

Full text: Strategies have been used to control dissolution rate of drugs, which in the case of oral delivery systems, results on micro or nano-encapsulated particles or even solid dispersions [1] between polymers and pharmaceuticals. It was demonstrated that polyurethane resin (PR) derived from castor oil plant can be used as a modulating agent in controlled-release formulations [2] . Domperidone (DOM), which is a drug used to suppress vomiting, has been incorporated into the PR. The X-ray total scattering and PDF method has been applied to evaluate the miscibility in the solid dispersion [1] , and here it was used to evaluate PR/DOM system. Three samples were analyzed: DOM raw material, pure PR and a solid dispersion PR/DOM. It was used two X-ray radiation energies, CuKa (8 KeV) and Synchrotron (20 KeV). The program PDGgetX2 [3] was used to get PDF patterns of the samples and to model the crystalline (DOM) and amorphous (PR) structures. Others analyses were used, as FTIR spectroscopy and scanning electron microscopy (FEG) to corroborate with results obtained by PDF. Preliminary results demonstrate that DOM and PR are forming an immiscible solid dispersion and that X-ray of high energy is necessary to obtain trustable results in the analyses. References: [1]. A Newman, D Engers, S Bates, I Ivanisevic, RC Kelly, G Zografi. Characterization of amorphous API:Polymer mixtures using X-ray powder diffraction. JPharmSci. 97(11):4840-4856, 2008. [2]. HG FERRAZ, M C Caetano-Jr. Formas Farmacêuticas de liberação controlada, composição farmacêutica de liberação controlada, processo de obtenção de forma farmacêutica de liberação controlada e uso de derivados de óleo de mamona em formas farmacêuticas de liberação controlada. PI 0604670-3. BR. Out. 2006. [3]. X Qiu, JW Thompson, SJL Billinge. 2004. PDFgetX2: a GUI-driven program to obtain the pair distribution function from X-ray powder diffraction data. J. Appl. Cryst. 37(4):678. (author)