Comparative Study of Biological Activity of Four Botulinum Toxin Type A Preparations in Mice

Abstract

Units of available botulinum toxin preparations are not interchangeable, and the dose-conversion ratios between such preparations remain controversial. To compare the efficacy and safety of four botulinum toxin type A preparations. Murine gastrocnemius compound muscle action potentials (CMAPs) were recorded before and after injecting the four botulinum toxin preparations (onabotulinumtoxinA, abobotulinumtoxinA, new botulinum toxin, and incobotulinumtoxinA). In all preparations, CMAP amplitudes decreased until 4days after receiving the injection and then gradually recovered. On postinjection day 84, the amplitudes returned to baseline in all groups except the high-dose groups. CMAP amplitude in the contralateral limb also decreased up to postinjection days 4 to 7 and then gradually returned to baseline by postinjection day 28. The dose-conversion ratio between onabotulinumtoxinA and abobotulinumtoxinA was determined to be 1:2.6; previous reports of 1:3 were considered too high. A dose-conversion ratio between onabotulinumtoxinA and new botulinum toxin of 1:1 was deemed appropriate. OnabotulinumtoxinA and incobotulinumtoxinA demonstrated a dose-conversion ratio of 1:1.07. The efficacy of incobotulinumtoxinA was slightly lower than that of onabotulinumtoxinA. These dose-conversion ratios are applicable solely from an efficacy standpoint and not for safety. This study was conducted in mice, so it may not translate perfectly to human applications.