Reconstituted botulinum type A neurotoxin: clinical efficacy after long-term freezing before use.

Botulinum neurotoxin type A (BoNT/A) is injected into muscles of facial expression for treatment of facial wrinkles. Manufacturers' recommendations state that the product should be used within 4 h of reconstitution to prevent loss of effectiveness. A prospective study was undertaken to evaluate the effectiveness of reconstituted BoNT/A when preserved in a frozen state for up to 6 months, as compared with nonfrozen BoNT/A used within 4 h after reconstitution. Treatment of 118 sites in 80 patients was performed and evaluated for aesthetic efficacy. Excellent results were observed in 94.8% of sites treated with nonfrozen BoNT/A and in 93.3% of the sites treated with frozen and thawed BoNT/A (p = 1). Minor side effects were rare and transient in both groups. In contrast to common belief, reconstituted BoNT/A may be frozen, thawed, and injected without losing its potency for up to 6 months, with efficacy equivalent to that of freshly prepared BoNT/A.