How Can You Perform Drug Release Testing of Creams, Ointments, and Gels?

When you're discussing dissolution, it is usually about solid oral dosage forms. Dissolution units can actually be used for any product which releases a drug over time such as medical devices, injectables, and semisolids. The USP has a chapter dedicated to testing semisolids which is USP General Chapter <1724> Semisolid Drug Products - Performance Tests.  This chapter discusses different methods to perform this testing such as the Franz cells and the Enhancer Cells. I'll focus on the Enhancer cell in this post.

The Enhancer Cell is unique among the semisolid testing options since it is the only system that can be used on a traditional dissolution bath. The enhancer cell is a chamber where a semisolid is placed with a membrane of your choice fitted on top. The floor of the cell raises and lowers to help load the semisolid evenly and help to prevent air bubbles. This cell is normally used with the 200mL flat-bottom mini-vessel and mini-paddle set-up, but some do use this in traditional 1L vessels as well. The cell comes in multiple surface area options depending on how much drug needs to be loaded into the cell to constitute a dose.

It is key when working with semisolids (or any testing that includes a membrane such as transdermals) that you take special care to ensure there are no air bubbles caught between the drug and membrane. Air bubbles will cause an inconsistent surface area and lead to variability. Also, be careful with the membranes as well so that they don't rip or tear.

The Enhancer Cell offers a lower-cost, more flexible, and much less delicate testing option for these semisolid products as compared to Franz Cells. Also, since this works on a normal dissolution bath you have all the options for autosamplers, Online UV, of Fiberoptic analysis!

Read also: Guide to Determine Sink Conditions in Dissolution Testing

Resource Person: Ken Boda (Dissolution Product Specialist at Agilent Technologies)

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