Amorphous Drug Preparation Methods

Hot-melt extrusion (HME) as continuous melt manufacturing process is preferable and industrially applicable. Single- or twin-screw extrusion and hot-melt co-extrusion are widely adopted techniques in pharmaceutical technology. Conveying of solids, melting, mixing, devolatilization, pumping and pressurization are main stages of HME. In principle, extrusion equipment usually consists of motor as a drive unit, an extrusion barrels enclosing rotating screw(s), an extrusion die and electronic control unit [1]. For better dispersive mixing specialized mixing elements are also used. The barrel can be independently heated and cooled by control system. The design variables concerns extruder, screw and die. The twin-screw extruder has two agitator assemblies mounted on parallel shafts which can rotate together in the same (co-rotating) or opposite directions and can be fully intermeshing. The diameter of screws which determine the size of equipment, and length of screws to diameter ratio (L/D), usually ranging between 20–40:1, are primarily defined. Modification of screw configuration affects the modification of manufacturing method leading to the process optimization for the planned application. Some examples of extruders modification are depicted schematically in Fig. 4.1. Commercial extruders have modular design that makes possible modification of the process under particular requirements [2].