Addition of an anesthetic agent to enhance the predictability of the effects of botulinum toxin type A injections: a randomized controlled study.

OBJECTIVE

To determine whether the paralyzing effect of botulinum toxin type A reconstituted in a solution of lidocaine with epinephrine is as effective as that of the same toxin reconstituted in saline and to determine whether the addition of lidocaine with epinephrine enhances the predictability of outcomes of botulinum toxin injections.

SUBJECTS AND METHODS

This double-blind, within-subject, randomized controlled study was conducted in 10 volunteer subjects. Lidocaine was added to botulinum toxin type A to achieve an immediate paralyzing effect on the injected muscle, and epinephrine was added to minimize diffusion of the injected toxin to adjacent muscles. This combination of agents was injected to temporarily paralyze the frontalis, corrugator supercilii, and procerus muscles on 1 side of the forehead of the 10 volunteers. The contralateral side was injected with the same dosage of the toxin, reconstituted in an equal volume of saline, to serve as control. Photographic and video documentation of the drugs' effects was obtained before injection and at 5 to 10 minutes, 1 week, and 3 months after the injections.

RESULTS

Immediate paralysis ensued on the experimental side (botulinum toxin type A + lidocaine + epinephrine) in all 10 volunteers. As assessed by 3 blinded evaluators, the extent of immediate paralysis resulting from the anesthetic agent was predictive of the extent of delayed paralysis resulting from the botulinum toxin. The botulinum toxin-induced paralysis wore off symmetrically in all subjects.

CONCLUSION

The injection of botulinum toxin reconstituted in lidocaine with epinephrine provided the physician immediate feedback on the extent of paralysis to be expected from the chemodenervating action of the botulinum toxin. This may enhance the safety and predictability of botulinum toxin injections in many applications.