Effects of operational conditions on the supercritical solvent impregnation of acetazolamide in Balafilcon A commercial contact lenses

In this work we employed a supercritical solvent impregnation (SSI) process using a scCO2 + EtOH (5% molar) solvent mixture to impregnate acetazolamide (ACZ) into commercially available silicone-based soft contact lenses (Balafilcon A, Pure Vision™, Bausch & Lomb®). Contact lenses (SCLs) drug-loading was studied at 40 °C and 50 °C, and from 15 MPa up to 20 MPa, and using low depressurization rates in order to avoid any harm to SCLs. The effect of impregnation processing time on the loaded ACZ amounts was also studied (1, 2 and 3 h). In vitro drug release kinetics studies were performed and the released ACZ was quantified spectrophotometrically. Several analytical techniques were employed in order to characterize the processed and non-processed SCLs in terms of some of their important functional properties. Obtained results demonstrated that ACZ-loaded therapeutic Balafilcon A SCLs can be successfully prepared using the employed SSI process. Furthermore, it was possible to control ACZ loaded amounts and, consequently, to adjust the final ACZ release levels into the desired therapeutic limits, just by changing the employed operational conditions (P, T, processing time and depressurization rate) and without change some of their most important thermomechanical, surface/wettability and optical properties. Obtained soft contact lenses can be potentially employed as combined biomedical devices for simultaneous therapeutic and correction of refractive deficiencies purposes.