RECONSTITUTED BOTULINUM TOXIN TYPE-A DOES NOT LOSE POTENCY IN HUMANS IF IT IS REFROZEN OR REFRIGERATED FOR 2 WEEKS BEFORE USE

Botulinum toxin type A (BTX-A) (Botox, Allergan, Irvine, CA) labeling recommends its use within 4 hours of reconstitution. Since BTX-A is av ailable only in 100-unit vials, a substantial quantity is often discar ded. Using eight volunteers, we measured the percent decline in extens or digitorum brevis (EDB) M-wave amplitude (percent paralysis) followi ng injection of freshly reconstituted BTX (right EDB) and compared thi s with the decline following injection of BTX that was refrozen (-20 d egrees C) or refrigerated (+4 degrees C) for 2 weeks (left EDB) after reconstitution. When analyzed as paired data, there was essentially no difference in the muscle paralysis resulting from fresh BTX compared with refrozen or refrigerated BTX, and no statistical difference betwe en groups was noted. Reconstituted BTX-A that is subsequently refriger ated or refrozen for 2 weeks does not lose potency in humans.