Well. It may very well have been a nerve agent of some description that got Navalny. In which case, Omsk was negligent and should've picked up on it. Could be any one of a number of organophosphate or carbamate compounds, not just the military agents. https://twitter.com/maxseddon/status/1297902806775496705

By definition nerve agents are acetylcholinesterase inhibitors. Also, by definition, most are not "toxins" - this word is getting badly abused these days.

There are numerous chemicals in this category, including some that are pharmaceuticals.

Worth looking at both pesticides and pharmaceuticals in this category, such as were used in Bulgaria and Rhodesia. https://www.bellingcat.com/resources/articles/2019/02/19/pesticides-as-poisons-analysis-of-the-debrev-case/

Gastrointestinal absorption of nerve agents gets less play in military medical books, as chemical weapons were generally designed for inhalation and/or dermal absorption.

Questions on effective dose, rate of effect, etc. will depend greatly on which chemical(s) were used. Indeed, it could have been a cocktail of things. Lots of variables we don't know.

Lethality may even not be an intended outcome. Sometimes these things are meant for intimidation.

In any case, it appears that poor Mr. Navalny is getting good care. Omsk wasted a lot of time. Whether they did it on purpose or out of negligence or some cuvee of the two, remains to be seen.

The chemicals in this family fall into 2 broad categories: organophosphates and carbamates.

The chemicals that have "good" properties for use as chemical warfare agents (e.g. Sarin, VX, etc.) may not necessarily have the best properties for use in a conventional poisoning by means of food/drink

Also, a lot of you are using the word toxin in wrong ways. Very few of the nerve agents are toxins. Although one of them, physostigmine, would be a suspect here.