Was Alexei Navalny poisoned with Novichok?

The medical staff treating Navalny, who reported on Thursday that he might have been poisoned with a nerve agent, suspect an as-yet-unidentified cholinesterase inhibitor. Navalny's suspected poisoning is in many ways similar to the attack on former Russian double agent Sergei Skripal in Salisbury, England two years ago.

Skripal is believed to have been poisoned with a Novichok nerve agent, which blocks the body's production of cholinesterase, an enzyme that is essential to the functioning of the nervous system. If untreated, such poisoning can be lethal.

What happens in nerve poisoning?

Cholinesterase breaks down acetylcholine in the human body, which functions as a neurotransmitter that plays a key role in waking up, focusing our attention, and many other processes. If acetylcholine is no longer broken down, the nervous system is overwhelmed with information. This makes normal nerve-muscle, nerve-gland and nerve-heart function impossible.

A person poisoned with a cholinesterase inhibitor will suffer excessive saliva production and breathing problems, as he or she will no longer be able to breathe normally. Left untreated, such poisoning can cause paralysis, seizures and death.

How can this be treated?

Medical staff must ensure patients do not suffocate from a seizure of their respiratory muscles. Navalny was put on a ventilator right away for this reason.

Doctors then administer atropine, an alkaloid that occurs in plants such as deadly nightshade and jimsonweed. It binds to the cells' muscarinic acetylcholine receptors, which counteracts the acetylcholine overstimulation. This treatment must continue until the body's cholinesterase begins breaking down acetylcholine again. Doctors often supplement this treatment by administering pralidoxime, a salt that boosts cholinesterase production.

Which other toxins contain cholinesterase inhibitors?

Toxic cholinesterase inhibitors are found in snake venom, insecticides, but also in chemical weapons like sarin and VX. Doctors therefore treat such poisoning with atropine and pralidoxime as well.

Beneficial cholinesterase inhibitors

Very low doses of cholinesterase inhibitors are given to patients suffering from Alzheimer's disease and Myasthenia gravis, a neuromuscular disease causing muscle weakness. In such instances, increased acetylcholine production is desirable.