Exploring the preparation of griseofulvin CAMS with amino acids of different hydrophobicity as co-formers using a modified hot-melt extrusion process.

Co-amorphous systems (CAMS) of griseofulvin (GRI) with the amino acids (AA): L-lysine (LYS), L-valine (VAL) and L-methionine (MET) of increasing hydrophobicity were prepared using a solvent assisted hot-melt extrusion (HME). Co-formability was evaluated by thermodynamic miscibility prediction, thermal analysis (DSC), powder crystallography (pXRD) and vibrational spectroscopy (ATR-FTIR). Decomposition temperature range was defined by thermogravimetry (TGA) and DSC. Solubilities of crystalline and amorphous drug were determined by the UV-extinction method. The physical stability of GRI/AA CAMS was evaluated by accelerated tests and for ratios 1:1 and 1:2 was excellent. Non-sink dissolution tests of equimolar CAMS of the more hydrophobic MET and VAL revealed long lasting supersaturation, above the solubility of amorphous drug, whereas ratios 2:1 and 1:2 gave lower supersaturation due to partial recrystallization during dissolution, despite the good physical stability. CAMS of the hydrophilic LYS were physically stable but showed poor dissolution, possibly due to self-association of LYS in water. Addition of wetting agent in the dissolution medium improved dissolution without altering the profile. Since previous attempts to formulate GRI/AA CAMS with purely mechanical methods found only moderate success, the feed pretreatment HME method employed in this work makes an excellent alternative for drug/AA CAMS where mechanical or solvent evaporation methods fail.