Objective: To determine whether injection with botulinum toxin type A (Botox; Allergan Inc, Irvine, California) reconstituted with preservative-free saline (0.9% isotonic sodium chloride) after 2-week cold storage in a refrigerator (4 degrees C) or freezer (-20 degrees C) is less efficacious than injection with freshly reconstituted Botox.
Methods: We conducted a prospective, double-blind, randomized controlled trial at an academic facial plastic surgery practice with 40 volunteers for treatment of horizontal forehead rhytids, each acting as his or her own control. In a blinded fashion each subject received freshly reconstituted Botox (control) on one side of the forehead (frontalis muscle) and 2-week-old reconstituted Botox (experimental) stored at 4 degrees C (refrigerated) or stored at -20 degrees C (frozen) on the other side. The right and left forehead movement was measured and photographed at rest and during maximum contraction of the frontalis muscle prior to Botox administration and on follow-up days 14, 30, 60, 90, and 120 after injection. Each participant also completed a questionnaire regarding right and left forehead movement prior to injection and at each follow-up visit.
Results: No significant difference was noted for any subject in the timing of onset or duration of action or the measurable reduction of forehead movement between the fresh and 2-week-old refrigerated Botox or between the fresh and 2-week-old frozen Botox. The subjects had a gradual return of muscle function over the 4-month follow-up period.
Conclusions: No measurable difference was found in the potency or duration of efficacy of Botox in the treatment of forehead rhytids after 2 weeks of refrigeration or freezing compared with fresh reconstituted Botox. When Botox, fresh or stored, is given at an adequate dose to cause full paralysis of the desired muscle, the duration of the muscle paralysis is dependent on the physiologic rate for the motor nerve to reestablish neural transmission.