EFAC is a natural product called "Esterified Fatty Acid Complex" (also known by the chemical name cetyl myristoleate). It is a patented product (now expired) that has beneficial properties for treating joint pain and fibromyalgia.
Postscript
This edition of Doctor's Housecall aired live on KMOG radio FM103.3 and AM1420
in Payson, AZ between 5pm and 6pm MST (Arizona Time) on April 19, 2022.
Dr. Weyrich offers a free 15 minute consultation at
+1 (888) 391-0414
to discuss any comments or questions you might have about this broadcast (subject to
schedule availability).