Novel patch delivers local anesthesia with convenience, quickness, safety

New York-An easy-to-use, self-warming patch containing lidocaine and tetracaine provides effective local anesthesia for minor dermatological procedures in adult patients, said Brian Berman, M.D., Ph.D, at the American Academy of Dermatology's Academy '04 meeting here.

The local anesthetic patch is being developed by a Salt Lake City, Utah, biomedical company, ZARS, and is currently undergoing U.S. Food and Drug Administration review.

In a poster presentation, Dr. Berman and co-investigators presented the results of a multicenter, prospective, randomized, double-blind, placebo-controlled study in which patients undergoing a variety of minor surgical procedures requiring local anesthetic applied either the lidcoaine/tetracaine (L/T) patch or a placebo self-warming patch 30 minutes prior to surgery. Efficacy was assessed based on patient, investigator and independent observer ratings of pain and by comparisons of proportions of patients in each treatment group requiring rescue treatment intraoperatively with subcutaneous lidocaine. Ninety-four patients completed the study, and the analyses showed significant differences favoring the L/T patch over placebo in all endpoints. The only adverse event reported was transient moderate burning by a single patient in the active treatment group.

Only patients undergoing surgical procedures that would not require suture closure were eligible for the study. Excision was the most commonly performed procedure (~42 percent), followed by electrodessication, curettage and shave biopsy. Other procedures included skin tag removal, keloid injection and cryotherapy. Individuals with a history of allergy or sensitivity to lidocaine, tetracaine or adhesive, who had taken an analgesic prescription strength pain medication during the preceding 24 hours, or who had non-intact skin at the surgical site, were excluded.

Patient assessment The patient assessment was based on a rating of pain severity using a 100-mm visual analogue scale (0=none, 100=worst pain ever experienced), and the results showed users of the L/T patch experienced less pain than users of the control patch. The median VAS score for the L/T patch group was 5 compared with 31 for the controls.

The investigators and independent evaluators were asked to judge whether or not patients experienced pain during the procedure. The results for both groups of evaluators were consistent with each other and showed that slightly more than 50 percent of the controls experienced pain compared with only 10 percent of the subjects who had been treated with the L/T patch.

In addition, while nearly half of the controls required rescue anesthesia, less than one-fourth of the patients using the L/T patch needed to receive subcutaneous lidocaine injection. Anesthesia was rated as adequate by nearly three-fourths of the patients treated with the L/T patch, but by half that proportion among the controls.

The safety evaluations also included assessments of erythema or edema at the patch application site.

While these reactions were slightly greater after application of the L/T patch, the difference in severity compared with placebo was not statistically significant.

"Although this study demonstrates the L/T patch is effective for minor dermatological procedures in adults, its effectiveness in children who often fear injections, in surgery requiring placement of sutures or whether similar anesthesia could be achieved with less than 30 minutes of application requires further study," Dr. Berman says. The study was sponsored by ZARS.

Disclosure: Other than being a study investigator, Dr. Berman has no financial interest in the company.