Melt extrusion has been used in the plastics and polymers industry for decades. Advances in formulation enable poorly soluble drug molecules to be incorporated into solid dispersions using a polymeric carrier. Hot melt extrusion is an alternative to wet agglomeration, a good carrier for sustained release forms and taste-masked dosages. Extrusion processes can also create films for oral strips or dermal patches in a solvent-free process.

According to the US FDA, the continuous manufacturing process reduces human errors caused by starts and stops during the batch process. Continuous granulation is also safer and more reliable. In a continuous process, ingredients are fed and mixtures sent to downstream production. Extruders have been used in wet granulation processes for many years; twin-screw extruders are now playing a central role in pharmaceutical manufacturing.

Rheometry and spectroscopy play important roles in developing and implementing extruder-centered drug formulations. The use of near infrared (NIR) spectroscopy for the analysis of active ingredients in pharmaceutical formulations is well known. The technique is nondestructive, has excellent signal-to-noise ratios and can use fiber optics to take sampling to the process. NIR spectroscopy is an ideal choice to monitor the output of a hot melt extruder. Complementary to NIR in bulk and in-line sampling, Raman spectroscopy adds microscopic imaging to analyze tablet homogeneity and the analysis of co-extrusions.