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Saline with Preservative May Make Botulinum Toxin A Injections Less Painful

Patients reported less pain from injections of botulinum toxin A reconstituted with preserved saline than from injections reconstituted with preservative-free saline.

Botulinum toxin A (Botox) should be used within 4 hours of reconstitution with preservative-free saline (0.9% NaCl), according to the U.S. Food and Drug Administration (FDA)-approved package insert. However, many clinicians have found that botulinum toxin A maintains its potency for weeks after reconstitution. To keep reconstituted botulinum toxin A beyond 4 hours, using saline that contains preservative would seem prudent. These researchers evaluated saline preparations to see which is least painful to receive by injection.

Twenty patients who had previously received injections of botulinum toxin A reconstituted with preservative-free saline were recruited and injected with botulinum toxin A reconstituted with saline and the preservative benzyl alcohol. The patients were asked to compare the pain of the recent and earlier injections. Ninety percent of patients reported the injections that included preservative to be less painful than the preservative-free injections. The average reduction in pain was about 55%.

Fifteen other patients participated in a randomized, double-blinded study in which they received botulinum toxin A reconstituted with preservative-free saline on one side of the face and botulinum toxin A reconstituted with saline and preservative on the other side. These patients were asked to compare the pain of injection on each side. All patients reported less pain on the saline-and-preservative side, with an. average reduction in pain of 46%. In follow-up self-reports and subsequent clinic visits, no differences were found in efficacy, adverse effects, or duration of effect between the two sites.

Comment: With many physicians needing to keep reconstituted botulinum toxin A for more than 4 hours, the use of saline with preservative has become popular. The associated significant reduction in the pain of injection is a welcome bonus. Based on findings in current clinical practice and this research, botulinum toxin A reconstituted with benzyl-alcohol preserved saline (1) hurts less on injection, (2) retains its potency, if refrigerated, for a week or more after reconstitution, and (3) is just as effective as botulinum toxin A reconstituted with preservative-free saline. Clearly, the FDA-approved package insert is out of date and needs to be revised.

— George J. Hruza, MD

Published in Journal Watch Dermatology May 29, 2002

Citation(s):

Alam M et al. Pain associated with injection of botulinum toxin A exotoxin reconstituted using isotonic sodium chloride with and without preservative: A double-blind, randomized controlled trial. Arch Dermatol 2002 Apr; 138:510-4.

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