According to Dubai authorities, and as reported by ABC News, Hamas operative Mahmoud al-Mabhouh was given a shot of succinylcholine prior to other grossly things done to his body on the fateful (for him) day of January 19, 2010. And since your humble correspondent is an anesthesiologist by day, and by call at night, let me tell you why succinylcholine is such a perfect murder weapon.
The best poisons usually have three things in common: small effective dose, also called Median Lethal Dose (or LD50), ease of administration, and rapid and definitive action. The fourth characteristic, the difficulty in detection by a forensics team is a big premium that most poisons don’t posses. Most poisons, that is, except succinylcholine and maybe a few others.
So let’s review some science, shall we? Succinylcholine is a muscle relaxant. Anesthesiologists call it “sux”. Sux is commonly used before intubations, as it completely relaxes patients. Sux is a rapidly acting depolarizer that can be given intravenously (IV) or intramuscularly (IM). Once administered, succinylcholine circulates in the blood, reaches nicotinic receptors on the surface of muscle cells, and there it imitates the action of acetylcholine, a neurotransmitter that our nerves naturally release to make our muscles move. When succinylcholine is given, seconds later the patient fasciculates, and all muscles in his body become depolarized. In essence, sux makes every muscle twitch to the point that it becomes unresponsive to any subsequent stimulation: you can’t breathe, you can’t even blink.
Sux is highly effective. In IV form, 100 mg of sux will depolarize every muscle in the body of a 70kg man in about 20 seconds. And the patient will not be able to take another breath for at least 5 minutes. So without assisted ventilation, he is toast. The IM dose of sux is not much different, but takes a little longer to set in.
So there you have it: succinylcholine is an easy to inject poison, it is highly effective, and is guaranteed-to-work quick.
The fourth characteristic of succinylcholine is good news for assassins: sux is almost impossible to detect because its metabolites are all naturally occurring molecules. here’s how it works. Most molecules of succinylcholine break down in blood into succinylmonocholine and choline, thanks to a circulating enzyme called pseudocholinesterase. The process is so efficient that only a small fraction of sux molecules that were given actually reach neuromuscular junctions in the first place. Succinylmonocholine is subsequently hydrolyzed into succinic acid, or succinate, a naturally occurring substance well known to anyone who studied biochemistry. The reason succinate is so famous is because it is an important player in TCA (Krebs) cycle, a series of chemical reactions that powers all living cells that use oxygen.
Coming back to Mahmoud al-Mabhouh, he either had an abnormal genetic variant of pseudocholinesterase, which is not uncommon, so some of the sux was not metabolized, or Dubai authorities had access to a highly sensitive succinylmonocholine essay. Or someone, we think, is just bluffing in the Middle East. No surprises there.
Thanks for reading, and here’s a great spy movie, courtesy of Dubai authorities: