Quantitative Correlation Between Hyaluronic Acid Filler and Hyaluronidase

The hyaluronic acid-based filler (HA filler) is used worldwide in various applications. In particular, the HA filler is used in the plastics and cosmetic medical field for facial rejuvenation and contouring. In this setting, it is injected into the skin or underlying tissue. Complications of HA filler injection have been relieved using hyaluronidase. However, there is no standard dose to adjust for undesirable HA filler lumpness. In this study, the authors tried to analyze any quantitative correlation between HA filler and hyaluronidase. The back of each rat (total 14 rats) was divided into 4 sites. A volume of 0.5 mL HA filler was injected into the subdermal layer at each site and HA filler nodules were created on the dorsum of each rat. Each nodule was allocated to groups 1, 2, 3, and 4 according to the different concentrations of hyaluronidase. As a result, the injected HA filler volume doubled within 4 days of injection, and then decreased slowly thereafter in group 1 (control group with normal saline only). A 30 unit hyaluronidase treatment compensated for the initial volume increase (approximately 30%) with HA filler (0.5 ml) at the fourth day. Sixty units of hyaluronidase reduced the initial volume (0.5 mL) of overinjected or misplaced HA filler on the fourth day. Approximately 90 units of hyaluronidase can reduce to the volume by 0.25 mL (50%) of the injected HA filler on the fourth day. The authors believe that this quantitative analysis of hyaluronidase concentration is helpful to plan the amount of hyaluronidase for correction of HA filler injection errors.