In the first part, 12 healthy volunteers had 0.2 mL of NASHA gel injected into two sites, approximately 10 cm apart, on one forearm. One to 3 days after implantation, a blinded evaluator graded the cutaneous augmentation at both sites, and 75 units of hyaluronidase with thimerosal preservative were injected into one site and control saline into the other. Within 4 to 7 days of hyaluronidase injection, 80% of the NASHA gel had clinically disappeared at the hyaluronidase site, while 90% of the gel persisted at the control site. Fourteen days later, the median skin score at the hyaluronidase sites was 0 -- no clinically detectable gel.
The second part of the study was designed to measure the dose-dependent effects of hyaluronidase. Eight new volunteers received three 0.2-mL injections of NASHA gel, 3 cm apart, on one forearm. Three to 5 days later, a different concentration of preservative-free hyaluronidase (10, 20, or 30 units) was injected into each of the three implantation sites in each subject. Four to 7 days later, the 30-U sites had no palpable gel, and the 20-U and 10-U sites demonstrated dose-dependent reductions. By 14 days, the 20-U sites became clinically imperceptible, and by 4 weeks, the 10-U sites became imperceptible as well. About 25% of subjects in both parts of the study developed localized allergic reactions in the hyaluronidase-injected sites; the reaction was more pronounced with injections containing thimerosal.
Comment: Hyaluronidase injections were useful in reducing NASHA gel overcorrection. The desired level of flattening can be achieved by carefully titrating the dose, and larger doses completely eliminate NASHA gel effect from the implantation site. The injection can be done several days after implantation, when the procedure-associated edema has mostly resolved. Localized allergic reactions to hyaluronidase were frequent at the doses used. Patients with a history of allergy to bee venom or to the preservative should not be injected.
George J. Hruza, MD
Published in Journal Watch Dermatology August 9, 2005
References:
Vartanian AJ et al. Injected hyaluronidase reduces restylane-mediated cutaneous augmentation. Arch Facial Plast Surg 2005 Jul/Aug; 7:231-7.
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