Pharmaceutical Hot-Melt Extrusion

Extrusion processing technologies have long been used as a means of fabrication by the plastics industry to produce a range of products in an efficient yet cost effective manner. The versatile method of hot-melt extrusion (HME) has been broadly applied in the plastics industry, using heating element technology including quality cartridge heaters and band heaters, and is now being adopted by the pharmaceutical industries where the process is rapidly gaining in importance as a means of producing pharmaceuticals, especially in the preparation of a variety of dosage forms and drug delivery systems.

Expanding on insight from the plastics industry, formulators can extrude combinations of drugs, polymers and plasticisers into a variety of finished forms to attain required drug-release profiles. HME dosage forms are multifaceted fusions of live medicaments, functional excipients, and processing aids. HME using (often) bespoke heating elements offers a number of benefits over conventional pharmaceutical processing techniques and these include:

  • the absence of solvents
  • limited number of processing steps
  • continuous operation
  • possibility of the formation of solid dispersions and improved bioavailability
  • improved processing of low solubility substances
  • improvement in product quality while retaining optimum reproducibility
  • high economic efficiency

A crucial element to the pharmaceutical HME process is in selecting the correct polymers to obtain the desired drug-release profile and best facilitate extruder processing. Numerous pharmaceutical-grade polymers are available commercially that can be applied in HME formulations. The correct grade polymer will be selected based on the processing conditions and qualities of the material to be extruded, including its thermal properties, as the conditions chosen must create a satisfactory melt viscosity for processing, but must not result in the degradation of any raw materials.

Heating elements such as superior band and cartridge heaters, ensure the precise melt pressure(s) of the polymer is maintained as it is forced through the extruder to the die. Plasticisers that reduce the melt viscosity of the material are added to HME formulations so that it may be processed in the extruder at a lower temperature, reducing the possibility of product degradation issues associated with temperature-sensitive drugs or polymers.

HME equipment can be modified to generate optimum final dosage forms, including the screw configuration, type of extruder, temperature-zone set points along the extruder, and rate of extrusion. The entire HME process is fortified by the application of first-class band and cartridge heater technologies.

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