Mixing of Injectable Fillers: A National Survey

The mixing of hyaluronic acid or calcium hydroxylapatite fillers with normal saline, plain lidocaine, or lidocaine with epinephrine before injection is a familiar practice among dermatologists. However, the frequency of this practice and rationale behind it has not been well studied.

To better elucidate the clinical practice of mixing fillers with other solutions before injecting among dermatologists.

A survey was electronically distributed to members of the American Society for Dermatologic Surgery.

Four hundred seventy-five dermatologists responded to the survey. Thirty-five percent of respondents mix fillers before injection. Solutions used were as follows: plain lidocaine (44%), lidocaine with epinephrine (36%), normal saline (30%), and sterile water (7%). Respondents mix filler for the following reasons: to decrease viscosity (40%), increase anesthesia (30%), decrease swelling (17%), and increase volume (13%).

Despite the lack of evidence, more than one-third of dermatologists surveyed mix fillers with other solutions before injection. Plain lidocaine is most commonly used. The top reason for mixing fillers is to decrease viscosity and facilitate ease of injection. More scientific data are needed to support this practice and better understand the biophysical changes that occur when mixing fillers with other solutions.