Compounding Hotline: Your Compounding Questions Answered
Author: Martin A. Erickson III, RPh
Q: I am a pharmacy student in Wisconsin, and at my current practice site we have several doctors who prescribe a topical cream [ketoprofen 10%, gabapentin 6%, lidocaine 5%, and amitriptyline 2% in VaniCream] for pain in our patients. The ketoprofen is very difficult to suspend in this mixture. Do you have any tips on preparation?
A: First, please check with the prescriber about the therapy. Is this preparation intended for penetration of the active ingredient into a joint or for systemic absorption? In either case, the vehicle you mentioned does not contain a penetration enhancer per se. You might find patients obtain improved relief if you use a vehicle containing a penetration enhancer (eg, PLO gel, Pentravan).
The ketoprofen and other active ingredients should be reduced to a fine, uniform consistency by means of comminution with a ceramic or Wedgwood (not glass) mortar and pestle, after which a smooth paste should be made by adding a small amount of ethoxydiglycol, which solubilizes the ketoprofen nicely.
If this preparation’s emulsion is “breaking,” 2 different approaches can be taken to remedy this:
1) Using lidocaine as the base molecule and adding lidocaine hydrochloride 50:50 is often beneficial. If you use this approach, check the molecular weights to be sure you are incorporating sufficient lidocaine.
2) Decreasing the concentrations of the active ingredients and administering a larger quantity to obtain the same dose can also help. PT
Mr. Erickson is director of professional affairs at Gallipot Inc.