The application of continuous extrusion via twin screw extruders (TSE) for pharmaceutical solid dosage form production is growing in popularity as a preferred option to more traditional granulation techniques. The TSE offers several advantages as a method of granulation formation including the continuous processing and combination of a variety of process steps within one piece of equipment, i.e. distributive and dispersive mixing, granulating and drying. Two methods in which the extruder is used for solid dosage form production are wet granulation and hot melt extrusion. During extrusion in both of these methods, liquids and powders must be fed accurately and continuously throughout the run and refill operations in order to ensure consistency of formulation, constant throughput, proper order of mixing ingredients and regulated mass transfer. K-Tron Pharmaceutical LIW feeders are used in conjunction with extruders in the pharmaceutical industry for both liquid and powder feeds. Typically, feed streams are introduced to the extruder in a “starve-fed” manner, where the rate is set by the feeders and is independent of the extruder screw speed.
Melt extrusion or “hot melt” extrusion is a process which has been popular for many years in the plastics industry. It has emerged within the pharmaceutical industry as a method to develop solid dosage forms without the use of water or solvents as liquid granulating binders. Instead, materials which melt at the extruder processing temperatures act as these binders. During the process of hot melt extrusion, a powder blend of the active pharmaceutical ingredient (API), a polymer, and various excipients is transferred by a rotating screw through the heated barrel of the extruder. The drug compound remains in a state of molecular dispersion as the polymer hardens. The extrudate can then be formed into a variety of shapes, including granules and pellets.