Two years after the death of Russian opposition leader Alexei Navalny, the UK and several European allies say they have identified the substance that likely caused it: a rare neurotoxin known as epibatidine. According to the UK Foreign Office, traces of the toxin were found in samples taken from Navalny's body following his death in a Siberian penal colony. The allies argue that only the Russian state had the "means, motive and opportunity" to deploy such a substance. Moscow has dismissed the accusation as an information campaign. But what is the dart frog toxin allegedly used to kill Alexei Navalny? Here's everything you need to know.
What is epibatidine?
Epibatidine is a powerful natural neurotoxin first isolated from the skin of a South American poison dart frog species, including the Anthony's poison arrow frog and the Phantasmal poison frog. The compound was originally discovered in frogs native to Ecuador and Peru. In the wild, these amphibians accumulate the toxin through their diet, producing alkaloids that are stored in their skin as a defense mechanism. Frogs raised in captivity do not produce epibatidine because they lack the necessary dietary sources. Toxicologists describe epibatidine as extraordinarily potent, estimated to be around 200 times stronger than morphine. Although it has been studied for potential use as a painkiller and in treating inflammatory lung conditions, it has never been approved for clinical use due to its extreme toxicity.
How does it work?
Epibatidine targets nicotinic acetylcholine receptors in the nervous system. These receptors are critical for transmitting signals between nerves and muscles. When overstimulated, they can trigger severe symptoms including muscle twitching, seizures, paralysis, slowed heart rate and respiratory failure. In fatal cases, death typically results from suffocation as the respiratory muscles cease functioning. Experts say that detecting epibatidine in the bloodstream would strongly suggest deliberate administration. Its rarity and potency make accidental exposure highly unlikely.
How rare is it?
Epibatidine is considered exceptionally rare. It is found naturally only in specific poison dart frog species within a narrow geographic region of South America. Extracting it from wild frogs would require highly specific environmental and dietary conditions. The toxin can also be synthesised in a laboratory, but doing so requires advanced chemical expertise and facilities. According to toxicology experts, documented cases of epibatidine poisoning are extremely limited and largely confined to laboratory incidents, none of which were fatal.
What has Russia said?
The UK and allied European governments say laboratory testing confirmed the presence of epibatidine in Navalny's body. They maintain that only the Russian state could have obtained and deployed such a rare substance. The Kremlin has rejected the findings. Russian officials previously stated that Navalny died of natural causes. The Russian embassy in London dismissed the latest claims as politically motivated, while Kremlin spokesperson Maria Zakharova described them as an attempt to distract from Western domestic issues. Navalny, 47 at the time of his death, had been imprisoned for three years and was transferred shortly before his death to an Arctic penal colony. Russian authorities said he felt unwell after a walk, collapsed and did not regain consciousness.