Predicting final product properties of melt extruded solid dispersions from process parameters using Raman spectrometry

•Physically stable amorphous IR formulations of spironolactone were melt-extruded.•Degree of drug degradation was determined non-invasively by Raman spectrometry.•Transmission and confocal Raman spectrometry were compared for the measurement of residual drug crystallinity.•Raman spectrometry could well estimate the glass-transition temperature of solid dispersions.•Dependence of drug degradation and residual crystallinity on extrusion parameters was statistically described.

Raman spectrometry was utilized to estimate degraded drug percentage, residual drug crystallinity and glass-transition temperature in the case of melt-extruded pharmaceutical products. Tight correlation was shown between the results obtained by confocal Raman mapping and transmission Raman spectrometry, a PAT-compatible potential in-line analytical tool. Immediate-release spironolactone–Eudragit E solid dispersions were the model system, owing to the achievable amorphization and the heat-sensitivity of the drug compound. The deep investigation of the relationship between process parameters, residual drug crystallinity and degradation was performed using statistical tools and a factorial experimental design defining 54 different circumstances for the preparation of solid dispersions. From the examined factors, drug content (10, 20 and 30%), temperature (110, 130 and 150 °C) and residence time (2.75, 11.00 and 24.75 min) were found to have significant and considerable effect. By forming physically stable homogeneous dispersions, the originally very slow dissolution of the lipophilic and poorly water-soluble spironolactone was reasonably improved, making 3 minute release possible in acidic medium.

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