Screening of Polymers for Oral Ritonavir Amorphous Solid Dispersions by Film Casting

<b>Background/Objectives:</b> Drug-polymer interactions and miscibility promote the formation and performance of amorphous solid dispersions (ASDs) of poorly soluble drugs for improved oral bioavailability. The objective of this study was to employ drug-polymer interaction calculations and small-scale experimental characterization to screen polymers for potential ASDs of ritonavir. <b>Methods:</b> Seven polymers across four polymer types were screened as follows: an enteric one (EudragitS100), amphiphilic ones (HPMCAS-L, HPMCAS-H, and their 1:1 combination), hydrophilic ones (PEG-6000, PVP-VA), and a surfactant (Soluplus), including PVP-VA as a positive control, as the commercial ASD employs PVP-VA. Drug-polymer interaction calculations were performed for Hansen solubility parameter, Flory-Huggins parameter, and glass transition temperature. ASDs were prepared via film casting. Experimental characterizations included drug solubility in polymer solutions, polymer inhibition of drug precipitation, polarized light microscopy, differential scanning calorimetry, solubilization capacity, and dissolution studies. <b>Results:</b> HPMCAS-L, HPMCAS L:H, and Soluplus, along with the positive control PVP-VA, were identified as polymers for potential ASDs of ritonavir, with HPMCAS-L and PVP-VA being preferable. HPMCAS-L and the positive control PVP-VA were always viable for both 20% and 40% drug loads across all tests. Films with each of these four polymers showed improved dissolution compared to amorphous ritonavir without polymer. Drug-polymer interaction calculations anticipated the unfavorable small-scale experimental results for PEG-6000 and EudragitS100. <b>Conclusion:</b> Overall, the results contribute towards a resource-sparing approach to identify polymers for ASDs.