Russian opposition leader Alexey Navalny was poisoned, Berlin hospital says

German army emergency personnel load the stretcher that was used to transport Russian opposition figure Alexei Navalny into an ambulance on August 22, 2020 at Berlin's Charite hospital.

On Friday, Anatoly Kalinichenko, the deputy chief physician at the Russian hospital where Navalny was being treated told a news conference that no poisons were found in Navalny's blood or urine. "We don't believe that the patient suffered poisoning," Kalinichenko told local journalists.

"Poisons or traces of their presence in the body have not been identified. Probably, the diagnosis of 'poisoning' remains somewhere in the back of our minds. But we do not believe that the patient suffered poisoning," he added.

What are cholinesterase inhibitors?

Andrea Sella, professor of inorganic chemistry at University College London, told CNN that cholinesterase inhibitors are widely used in two categories of insecticides: organophosphates and carbamates.

"Organophosphate insecticides poisonings are common worldwide, as farmers sometimes mishandle them. But some organophosphates are far more poisonous than insecticides and have been used for military purposes e.g. sarin, VX and Novichok," he said.

"We're talking about a very broad range of materials," Sella added.

The inhibitor acts on the nervous system in place of the critical acetylcholinesterase (AChE) enzyme, which transmits signals within biological systems. "The inhibitor attaches itself in the same place where the enzyme should be and the enzyme becomes irreversibly blocked," said Sella.

"It's one of the first thing they should have checked in Omsk. There are a number of symptoms that accompany this poisoning including various types of muscle paralysis, contraction of the pupil in the eye, blood tests, and so on."

The Charite Hospital in Berlin said in its Monday statement that Navalny is being treated with the antidote atropine.

Sella added that the atropine treatment is used to calm the nervous system and act against overstimulation, and agents such as Pralidoxime are used to reverse the attachment of the inhibitor and restore the activity of the AChE enzyme.

"If you don't act quickly you could have long-term damage associated with the nerve system," Sella added. "Navalny was treated and kept alive, yes, but whether or not if he'll have further damage remains to be seen."