Can I Develop Resistance To Botox?

Q: Dr. Eppley, I seem to be resistant to Botox . Recently 50u was injected into my masseter muscle on both sides and very minimal improvement was seen. It has been a month now and the ever so slight response is disappearing. I have a long and fond history with Botox for my masseter muscles even before it was approved for this use in the US. My last Botox of 100u was diluted with 1cc NS, a more concentrated mix compared to the previous times which was 100u with 1 1/2 cc NS. Should I go for Xeomin now and should I start with 100u for both sides? What is your take on this?

A: In my experience, Botox has worked well for masseteric muscle hypertrophy and I have not seen any patient that has developed a proven resistance to the drug. While it is entirely possible that you may be that rare patient that has developed such a resistance, there are other factors that can also affect how well Botox work. Reconstitution and the age of Botox since it was reconstituted are common culprits that can affect its potency. I would also question why such a concentrated dose was used this last time when the diffusion of Botox is not that great. It is important when injecting the masseter because of its muscle size to cover as much of the lower half of the muscle as possible. A less concentrated mixture with more injections may prove more effective. If this is not effective then I would consider changing to Dysport or Xeomin.

By the way, the use of Botox for masseter muscle hypertrophy and spasm is not an FDA-approved use even to this day. This is an off-label use of the drug.

Dr. Barry Eppley

Indianapolis, Indiana