UMEM Educational Pearls

Title: Deadly in a drop!

Category: Toxicology

Keywords: Botulinum, Dimethylmercury, VX, Tetrodotoxin (PubMed Search)

Posted: 8/17/2017 by Kathy Prybys, MD (Updated: 8/31/2017)
Click here to contact Kathy Prybys, MD

Botulinum

Most poisonous substance known to man
LD50 oral dose 1 mcg/kg
Heat labile single polypeptide chain undergoes proteolytic clevage irreverisibly binds and blocks cholinergic transmission causing a deadly neuroparalytic syndrome
Rx: Botulin antitoxin (equine derived against Clostriduim botulinum A,B,E)

Dimethylmercury (CH3)2 Hg

Highly toxic, restricted availability is rapidly absorbed and metabolized to methylmercury crosses CNS
LD50 of 50 mcg/kg means a dose as little as 0.1ml can result in severe poisoning
Death of Darmouth inorganic chemist Karen Wetterhahn who spilled a few drops on back of her latex gloved hand, quickly permeated, and absorbed causing severe neurotoxocity and death 10 months later
Rx: Chelation

VX ("venomous agent X")

Organophosphate nerve agent has been used as chemical weapon
Colorless, odorless, low volatility, and high lipophilicity
LD50 of 0.04mg/kg (10 mg). Death can occur within 15 minutes after absorption
Blocks acetylcholinesterase enzyme causing excess accumulation of acetylcholine at the neurojunction and cholinergic poisoning
Rx: Decontamination, Atropine, 2-PAM

Tetrodotoxin

100 fresh and salt water varieties (pufferlike fish/blue ringed octopus, frogs)
Heat stable, water soluble found in fish skin, liver, ovaries,intestine, and muscle
25 mg (0.000881 oz) expected to be lethal to a 75 kg person
Neurotoxicity by inhibition of Na-K pump and blockade neuromuscular transmission
Rx: Supportive measures

LD50 expresses the dose at which 50% of exposed population will die as a result of exposure.

Sep;90(9):2131-45. doi: 10.1007/s00204-016-1772-1. Epub 2016 Jun 27.

The need for empriricaly derived permeation data for personal preotective equipment. Blayney MB. Appl Occup Environ Hyg. 2001 Feb:1692): 233-236.

Death by food. Byard RW. Forensic Sci Med Pathol. 2017. Jul 15 doi: 10.1007/s12024-017-9899-9 [Epub ahead of print].