Volume 102 - What is Hot Melt Extrusion?

What is Hot Melt Extrusion?

Extrusion is a very common manufacturing operation across multiple industries. It’s a shaping process where an object is created (or extruded’) across a fixed cross-sectional profile. A good example of this is tubing or piping manufacturing. An unshaped material (blank) is pushed through a die, creating the final product (extrudate). A more, close to home example would be a garlic press or when you form noodles.

The ultimate goal of extrusion is to form a specific shape of a product. The extrudate can then be cut into desired lengths. This process can occur at different temperatures, leading to three types of extrusion: Hot, Warm, and Cold.

For the purposes of pharmaceuticals, specifically Drug Product manufacturing, we will focus on Hot Extrusion.

HME Simple Process Diagram
HME Process Hot Melt Extrusion

The hot extrusion used in pharmaceuticals is called Hot Melt Extrusion (HME). The main principle of HME is that you are mixing and melting the API and a polymer together. This polymer helps in dispersing the API in the extrudate before it goes into further processing. A Hot Melt Extruder operates with two screws (like an auger) that are mixing the API and polymer. The mechanical energy created by the screws helps to melt the mixture (hence ‘Melt’ in the name). Once the mixture is melted and mixed together, it is then pushed through a calendar roller and formed into a sheet of pellets – the extrudate. From there the sheet is cooled and broken apart into induvial pellets to be further processed down stream.

Why do we use it?

One of the big reason HME is used for oral drug products is that each drug can have a different solubility (ability to dissolve in a liquid) and intestinal permeability (how much drug passes through the intestine to the body).

Based on those two factors, a drug is classified into 1 of 4 classes in the Biopharmaceutical Classification System (BCS). Drugs in Class II and IV have low solubility (and low permeability for class IV) and HME can help improve that. The extrudate from the HME equipment will be an amorphous solid dispersion (ASD), a distribution of drug molecules within a solid (the polymer).

The extrudate will be a uniform distribution of the drug in the solid pellets, which is necessary for effective down stream processing. This also carries benefits for the bioavailability, amount of drug that enters circulation, as an ASD helps improve its solubility and dissolution (ability to dissolve).

HME Extruder Calendar Roller
Biopharmaceutical Classification System

Benefits of HME

  • Efficient process to create an ASD
  • Equipment has a small footprint
  • Continuous Process
  • High process understanding and control
  • Doesn’t require the use of solvents

Key Considerations for HME

  • API Properties – both physical and chemical
  • Polymer properties – how the polymer affects the manufacturability and final properties of the drug product
  • Critical Quality Attributes – Uniformity, Moisture, formation of degradation products
Person holding tray of finished products via hme process
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Vision.
Expertise.
Success.

Hot Melt Extrusion (HME) is a unique technology that enhances the bioavailability of poorly soluble APIs. AbbVie Contract Manufacturing offers proprietary hot melt extrusion (HME) technology in both the US and Europe.

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