Use of the Synera patch for local anesthesia before vascular access procedures: a randomized, double-blind, placebo-controlled study.

OBJECTIVE: This randomized, double-blind, placebo-controlled, paired study compared the Synera patch, a drug delivery device comprised of an eutectic mixture of lidocaine (70 mg) and tetracaine (70 mg) whose onset is accelerated by a controlled heating device, with placebo. The objective of the study was to evaluate the efficacy of Synera in inducing local anesthesia before a vascular access procedure.

DESIGN: Before the vascular access procedures, adult volunteers randomly received a concurrent application of Synera and placebo to the right and left antecubital surfaces. Forty subjects received 20-minute treatments. After each vascular access procedure, efficacy evaluations were completed by the subject, investigator, and an independent observer. Median subject-reported pain intensity, using the visual analog scale scores (VAS, 0-100 mm scale) were significantly lower for Synera than placebo (5 mm vs 28 mm, P < 0.001).

RESULTS: Compared with placebo, more subjects reported adequate anesthesia following Synera (73% vs 31%, P = 0.002), and more subjects indicated they would use Synera again (70% vs 33%, P = 0.006). Investigators rated more subjects having no pain with Synera compared with placebo (63% vs 33%, P = 0.021), and more subjects having adequate anesthesia with Synera (60% vs 23%, P = 0.004). Independent observers rated 68% of subjects having no pain with Synera compared with 38% with placebo (P = 0.015). Side-effects were limited to localized pruritus and erythema. Erythema was more common with Synera than placebo (62% vs 42%, P = 0.018).

CONCLUSIONS: A 20-minute application of Synera consistently provided clinically useful anesthesia for vascular access procedures, and appears to be well suited for topical dermal anesthesia due to its reduced time required to produce adequate anesthesia and high subject and investigator acceptance.