Evaluation of Physicochemical Properties Following Syringe-to-Syringe Mixing of Hyaluronic Acid Dermal Fillers

Abstract

BACKGROUND Historically, soft-tissue hyaluronic acid (HA) fillers have been mixed with agents to reduce pain or alter physicochemical properties. OBJECTIVE Evaluate the impact of dilution and mixing on HA filler physicochemical properties. MATERIALS AND METHODS Crosslinked HA filler (VYC-20L, 20 mg/mL) was diluted to 15 mg/mL using saline through 5 or 10 passes between 2 syringes connected using a luer connector. Extrusion force, rheological properties, and microscopic appearance were assessed. Undiluted VYC-15L (15 mg/mL) served as the control. RESULTS Average extrusion force was higher for diluted VYC-20L versus the control, with an increase in slope for gel diluted using 5 passes (0.65) and 10 passes (0.52) versus the control (<0.1). For diluted samples mixed with 5 or 10 passes, the rheological profile was different between the 2 halves of the syringe, with the second half more elastic than the first half, compared with the consistent profile of undiluted samples. Microscopically, diluted VYC-20L samples seemed more liquid near the luer and more particulate near the piston compared with the control, which was smooth throughout. CONCLUSION In addition to potentially introducing contamination, diluting or mixing soft-tissue HA fillers yields a heterogeneous product with physicochemical characteristics that vary substantially throughout the syringe.

Rheologic and Physicochemical Characteristics of Hyaluronic Acid Fillers: Overview and Relationship to Product Performance

“… 18 Four rheologic parameters may be used as the primary measures of a gel's viscoelastic properties: G* (a measure of the overall viscoelastic properties), G′ (a measure of the elastic properties), G″ (a measure of the viscous properties), and tan δ (tan delta, a measure of the ratio of the elastic to viscous properties). 7 17 19 20 Using a rheometer, a twisting force is applied to a gel between two plates to measure these parameters 12 ( Fig. 1 ).…”

Standards for aseptic techniques in medical aesthetic practices in the Benelux: Consensus recommendations

“… The patient should be informed about the procedure and any potential safety issues that may occur—informed consent is vital The Board recommended that everybody helping, assisting, or involved in the treatment of patients should receive adequate support and training to minimize the risk of error Pre‐procedure, a welcoming, reassuring, and courteous attitude of the injector is important to engender trust Providing a good ambiance helps ensure the patient is relaxed and comfortable Injectable products from different manufacturers or with different mechanisms of action should not be mixed, as this can cause a change in physicochemical properties and a potential breach of sterility 23 Clinics should have a resuscitation protocol, especially if there is a risk of anaphylaxis The Board recommended that post‐injection advice should be provided to the patient both verbally and in writing Contact lenses only need removing if procedures require the use of a CO 2 laser (and with other warming devices like TIXEL®) For many patients, music (jazz/lounge) during a procedure can contribute to a more pleasant experience …”

“…Injectable products from different manufacturers or with different mechanisms of action should not be mixed, as this can cause a change in physicochemical properties and a potential breach of sterility 23 …”

How Much Does Filler Apparatus Influence Ease of Injection (and Hence, Potential Safety)?

“…The use of dermal fillers, indications, and associated adverse events have been extensively characterized in the existing literature. [9][10][11][12][13][14][15][16][17] This article concentrates on extrusion forces required to inject the filler. The following were key findings, discussed here individually for corresponding points in the respective Results section above:…”