What is epibatidine, and how did it kill Navalny? A guide to the frog neurotoxin that five countries say poisoned Russia’s opposition leader.
The poison used to kill Navalny
The United Kingdom, Sweden, France, Germany, and the Netherlands announced that a substance called epibatidine killed Alexey Navalny, the opposition leader who died in a Russian prison in February 2024. The discovery followed testing of biological samples that Navalny’s associates had smuggled out of Russia.
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What is epibatidine?
Epibatidine is a potent neurotoxin that disrupts nerve cell function.
Epibatidine accumulates in the skin of Epipedobates frogs, which are native to Ecuador and Peru, protecting the animals from predators.
Epibatidine is far more effective as a painkiller than morphine. However, the gap between an effective dose and a toxic one is so narrow that researchers abandoned it as a potential drug in the 1990s. Scientists — including some in Russia — have since explored safer derivatives.
In animal studies, toxic doses of epibatidine have caused elevated blood pressure, convulsions, respiratory arrest, and death.
Documented human exposure to epibatidine is extremely rare. The first known case occurred in 2010, when a laboratory worker who had handled the substance developed hives and sought medical attention. He survived after treatment with antihistamines.
At higher doses, epibatidine poisoning would likely resemble nicotine poisoning, producing symptoms such as confusion, wheezing, vomiting, tremors, muscle twitching, impaired coordination, agitation, and lethargy. Death may occur before the full range of symptoms develops.
Alexander Polupan, an intensive care specialist, told The Insider that the publicly available data about Navalny’s symptoms matches what is known about epibatidine’s effects:
The clinical picture is in some ways similar to poisoning by organophosphorus compounds, which include the Novichok poison used in the 2020 attempt to kill Navalny, but with a less pronounced muscarinic cholinergic component. [These effects include slowed heart rate, drops in blood pressure, bronchospasm, excessive salivation, urinary incontinence, diarrhea, nausea, vomiting, and impaired vision.] Atropine is essentially ineffective.
Epibatidine can cause poisoning through skin contact or injection — the method used in animal studies. However, the scientific literature has documented only these routes of exposure. Inhalation or ingestion would likely also cause poisoning.
Scientists in Russia have reported that epibatidine poisoning can be detected by analyzing blood, cells from the mouth, or urine samples.
Where did the Russian authorities obtain this poison?
Today, epibatidine can be synthesized in a laboratory, eliminating the need to harvest it from Ecuadorian frogs. Scientists at Russia’s Institute of Organic Chemistry and Technology — which developed the Novichok group of nerve agents — have reportedly synthesized epibatidine.
In its pure form, epibatidine is a powder that dissolves in certain liquids, including beverages.
Before Navalny’s death, no state was known to have used epibatidine as a weapon. However, the toxin’s properties make it well-suited for assassination.