  botulinum toxin is a protein and neurotoxin produced by the bacterium clostridium botulinum.   it is the most acutely lethal toxin known, with an estimated human median lethal dose (ld-50) of 1.3â2.1 ng/kg intravenously or intramuscularly and 10â13&nbsp;ng/kg when inhaled.  botulinum toxin (btx) can cause botulism, a serious and life-threatening illness in humans and animals. three forms of botulinum toxin type a (botox, dysport and xeomin) and one form of botulinum toxin type b (myobloc) are available commercially for various cosmetic and medical procedures. ==biochemistry and mechanism of toxicity== [[image:presynaptic cnts targets.svg|thumb|left|300px|target molecules of botulinum (bont) and tetanus (tent) toxins inside the axon terminal.[http://www.cdc.gov/ncidod/eid/vol11no10/04-1
Bacterial_toxins Biological_toxin_weapons Botulism EC_3.4.24 Muscle_relaxants Neurotoxins Plastic_surgery