Pre-injection topical anesthesia may decrease effect of Botox

Applying topical anesthesia before injecting botulinum toxin type A appears to decrease the efficacy of the treatment without providing a significant reduction in pain for patients, a randomized study suggests.

Mirwat S. Sami, MD, and colleagues in Houston evaluated patient discomfort and efficacy of botulinum toxin type A (Botox, Allergan Inc.) injections after applying either betacaine or a placebo ointment followed by cryoanalgesia. The study included 20 patients treated for facial cosmetic rhytid reduction and 20 patients treated for benign essential blepharospasm.

Investigators treated half of each patient's face with betacaine and the other half with placebo, with crossover treatments performed at 2.5 to 4.5 month intervals. A total of 120 injections were performed. Of these, a reliably identified treatment effect was noted on one side of the face by 80% of blepharospasm patients and 77% of cosmetic patients, "with the placebo-treated side providing better botulinum toxin type A effect approximately 90% of the time (P < .001)," the authors said.

For only 18 of the 120 injections did patients report more pain on one side of their faces, and only one patient believed the administration of analgesia was worthwhile, according to the study authors.

The study is published in the November/December issue of Ophthalmic Plastic and Reconstructive Surgery.