Well, human bodies would tend to get immune to any medications especially the ones fed to them repeatedly from time to time, including Botox, and that's most probably the very reason why it didn't work.
Anyway, Botox injections are actually composed mainly of Botulinum toxin that are in fact medical derivatives from Clostridium botulinum bacterium (which causes botulism) that have been intentionally abused before for the purpose of chemical warfare owing to its intense toxicity.
Hence, please consider the excerpts below :
"Botulinum toxin is among the most poisonous substances known. The toxin, which can be ingested or inhaled, and which disrupts transmission of nerve impulses to muscles, is naturally produced by the bacterium Clostridium botulinum. Certain strains of C. baratii and C. butyricum can also be capable of producing the toxin.
Botulinum toxin has become well known in recent years for two reasons. First, the toxin has become a weapon in the arsenal of terrorists. Contamination of food is one route for infection with the toxin. The toxin can also be released into the air, which was attempted on at least three occasions between 1990 and 1995 by the Japanese cult Aum Shinrikyo. The government of Iraq admitted to United Nations inspectors following the 1991 Persian Gulf War that tens of thousands of liters of botulism toxin had been produced and loaded into weapons. The toxin was the most numerous of all the biological weapons then developed by Iraq.
Paradoxically, the other reason for the toxin's fame is the use of the toxin as a cosmetic enhancement (i.e., "botox")."