ANALYSIS From novichok to the poison of the arrow frog. Why the choice of epibatidine in the case of Navalny marks a new phase in the chemical arsenal of the Kremlin.

The death of Alexei Navalny in an Arctic penal colony has long been shrouded in the official version of "natural causes," until five European states – the United Kingdom, Sweden, France, Germany, and the Netherlands – announced that laboratory analyses identified in his samples the neurotoxin epibatidine, a rare substance associated with poison dart frogs from South America. The new conclusion connects the death of Vladimir Putin's most well-known opponent to the deliberate use of an exotic toxin, signaling a shift from the previous novichok – the chemical weapon used against Navalny in 2020 and Sergei Skripal in 2018.

Epibatidine, from Ecuador in the lab

Epibatidine was initially isolated from the skin of a species of poison frog from Ecuador, part of the well-known family of amphibians used by indigenous communities to poison their hunting darts. Chemists were drawn to it precisely for the extraordinary combination of extremely potent analgesic effect – estimated to be up to 200 times more potent than morphine – and very high toxicity, which makes the line between "useful" dose and lethal dose extremely thin. Pharmacologically, epibatidine is an agonist of nicotinic acetylcholine receptors, disrupting normal nerve transmission. The result, at toxic doses, is a picture of seizures, muscle spasms, cardiac rhythm disturbances, respiratory paralysis, and ultimately, respiratory arrest, a profile that experts consulted by the BBC and other publications have described as "rapid and difficult to control" in the absence of a very early diagnosis. Although the story of the Ecuadorian frog has an evident media impact, the essential point is that epibatidine can be synthesized in the lab, without access to animals or the ecosystem of origin. The fact that the toxin is not found naturally in Russia, and its presence in Navalny's body has "no innocent explanation," as official statements emphasize, shifts the issue from the biological realm to that of political intent and chemical capabilities.

Why the Russians did not use novichok again to poison Navalny

Novichok designates a family of nerve agents, developed by the USSR in secret military programs and explicitly designed as chemical weapons, with a classic mechanism: inhibition of acetylcholinesterase, the enzyme that degrades acetylcholine, leading to generalized cholinergic crisis. Specifically, this type of poison "breaks" communication between nerves and muscles until the body gives in. These agents have already been integrated into Russia's public "dossier": the attack on Skripal in Salisbury and the first assassination attempt on Navalny in 2020 have been attributed by Western investigations to Russian services, with conclusions made public in government reports and at the OPCW (Organization for the Prohibition of Chemical Weapons). From this perspective, repeating the novichok scenario in 2024–2026 would have the disadvantage of predictability and traceability, at a time when Navalny was already a symbolic case in Russia's relationship with the West. Choosing a rare toxin, non-specific to Russia, with a clinical profile less familiar to Russian doctors in an isolated penal colony, could be seen as an attempt to delay the exact identification of the substance, while maintaining at the same time the advantage of high lethality and very small doses required. There is also a political element: novichok has already become, symbolically, the "signature" of a state that attacks its enemies with banned weapons, provoking sanctions and international investigations. The use of a natural toxin, initially recorded in pharmacology literature, could be perceived in Moscow as a step into a gray area: a less codified instrument in the public imagination as a chemical weapon, even though, legally, the Chemical Weapons Convention prohibits the use of biological toxins for offensive purposes.

Epibatidine vs. novichok: different signatures of the same creative state in the way of poisoning

The joint statement of the United Kingdom and the four European allies starts from a standard formula in such cases – "Russia had the means, motive, and opportunity" – but nuances it by explicitly referring to the fact that Navalny was in prison, under the total control of the state, which reduces alternative hypotheses to almost zero. In parallel, British officials quoted by the BBC and other publications emphasize that epibatidine does not exist in industry or in current civilian use and that obtaining it requires specialized laboratories, usually accessible to a state-type structure.

Comparing the two substances, the difference is less one of "severity" – both can kill in micrograms – and more one of strategic positioning: novichok is the classic military chemical weapon, already publicly incriminated, while epibatidine is an "exotic" toxin that, precisely because of its rarity, becomes incriminating in itself. If novichok points to a chemical weapons program inherited from the Soviet era, epibatidine suggests adaptability and creativity in the choice of means, as well as a willingness to invest resources to find substances that are harder to anticipate by Western experts. Moreover, the fact that Navalny survived novichok in 2020 and managed to turn this episode into a political counter-narrative – his return to Moscow, public arrest, trials – gives the poisoning in prison with epibatidine a component of final "correction" of the previous failure. Choosing a rarely used toxin, almost unknown to public opinion, seems to indicate a desire for maximum efficiency and minimal visibility at the time of death, even though it was inevitable that it would be investigated retrospectively by Western laboratories. The "unprecedented" nature of the killing with epibatidine Until recent revelations, epibatidine appeared in the specialized literature primarily as a study substance, tested in laboratory experiments and in medicinal chemistry research, but abandoned as a clinical analgesic due to excessive toxicity. Toxicologists interviewed by the BBC and other publications have emphasized that documented human exposure prior to Navalny's case was limited to isolated laboratory incidents, without links to assassination operations or to Russia. Thus, according to Meduza, the first known case of poisoning occurred in 2010 and was accidental. A laboratory worker had handled the substance and developed hives. He sought medical assistance. He survived after treatment with antihistamines.

Media analyses and government reports that followed the statement of the five European states treat the use of epibatidine in Navalny's death as a precedent – the first known case in which this toxin is explicitly attributed to a state murder. Unlike polonium-210, ricin, novichok, or other substances used in famous cases related to Russia, epibatidine has no history of use in assassinations, which amplifies the impression of a qualitative escalation of the chemical arsenal used against opponents.

In legal terms, introducing a natural toxin into a case of political murder attributable to a state strengthens the tendency to expand the interpretation of the Chemical Weapons Convention and the norms regarding biological weapons, which do not distinguish based on the natural or synthetic origin of the substance, but based on its offensive use. For Russia, this means that, beyond the political debate, a new technical dossier is accumulating in an already sensitive area – the use of toxins and nerve agents against adversaries, outside the battlefield.

Synthesis made with the help of a data monitoring flow provided by the media monitoring platform NewsVibe Romania. The analysis presented has been enhanced with the help of Machine Learning and Artificial Intelligence tools.