Five European countries have found out what caused the death of Kremlin critic Alexei Navalny. The neurotoxin works extremely quickly and is deadly.
Feb 25, 2026, 10:08Feb 25, 2026, 10:08
Russian opposition figure Alexei Navalny was poisoned in custody. Five European countries declared this in mid-February after they had tissue samples from Navalny’s body examined in laboratories. The governments of Great Britain, France, Germany, Sweden and the Netherlands continue to emphasize that only the Russian state had the means, access and motive to administer the poison to Navalny.
Russian opposition leader Alexei Navalny died at the age of 47 on February 16, 2024 from dart frog poison.Image: keystone
Governments have reported the case to the Organization for the Prohibition of Chemical Weapons (OPCW) because such use of toxins is a violation of international agreements. Russia denies the poisoning of the opposition figure and says his death was of natural causes.
Navalny was poisoned once in 2020. This was proven at the time by, among others, the Institute for Pharmacology and Toxicology of the German Bundeswehr. The opposition activist survived the attack thanks to the poison Novichok, which the Russian secret service has already used in other cases. There is evidence of the Novichok poison attack in London on double agent Sergei Skripal in 2018.
Second poisoning of Navalny with epibatidine
This time, however, it was not Novichok that was discovered in Navalny’s tissue samples, but rather epibatidine, the poison of the South American poison dart frog. “Epibatidine is a very strong neurotoxin,” says Claudia Seiden Schwanz, spokeswoman for the Bundeswehr’s support command.
The Anthony poison dart frog (Epipedobates anthony) produces the poison epibatidine in the wild.Image: Getty Images
Of course, this tropical frog does not live in Russia. “Epibatidine can also be produced artificially in specialized research laboratories,” says Seiden Schwanz. Epibatidine is easy to buy, adds Eva Ringler, associate professor at the University of Bern, who has been researching poison dart frogs for many years.
Epibatidine is a neurotoxin that acts directly on the synapses in the brain and activates the nerve cells there. In other words: The frog poison first causes severe overstimulation at the nerve switching points, followed by a complete breakdown of nerve conduction. That’s why the effect is extremely quick. “Not like the slow-acting, cell-dissolving venom of many snakes,” says Ringler, and Waxwing adds that epibatidion is extremely toxic: “Even very small amounts can be fatal.”
Strong symptoms that appear quickly
Typical symptoms of poisoning include restlessness, high blood pressure, rapid pulse, excessive salivation, tremors and muscle twitching. Severe seizures, loss of consciousness, muscle paralysis and circulatory problems can then occur.
The frog’s poison is 200 times more powerful than morphine.Image: www.imago-images.de
Death usually occurs due to respiratory arrest because both the respiratory muscles and the central respiratory drive in the brain are paralyzed. Additionally, the cardiovascular system can fail if the body is overloaded by cramps and lack of oxygen. Theoretically there would be an antidote to the poison, but it would have to be available very quickly, which is unrealistic.
“Epibatidine has a pain-relieving and anesthetic effect that is 200 times as strong as that of morphine,” says Ringler. That’s why the toxin was temporarily investigated in research as a possible strong painkiller, as Waxwing explains. However, the development was abandoned because the possibility of therapeutic use was extremely low. “The dose that relieves pain is very close to the dose that causes severe poisoning or death. Widespread use for therapeutic pain relief is therefore not in an appropriate risk-benefit ratio,” explains Seiden Schwanz.
Frogs absorb poison through food
Poison dart frogs, of which the poisonous ones live primarily in Colombia and Ecuador, cannot produce the neurotoxin themselves. They absorb the toxins from their food and store them in the skin. In their habitats in Central and South America, the frogs, which are only a few centimeters long, eat ants, mites, termites, small beetles, snails and worms. “Many of these animals contain alkaloids,” says Ringler. Alkaloids include nicotine and caffeine. Your animals at the University of Bern and those at Zurich Zoo are not poisonous because they do not receive this food.
Alkaloids have a stimulating effect on the nervous system.Image: Shutterstock
The toxic substances are passed on to the skin through digestion. This causes the frogs to become poisonous and secrete the epibatidine again through special skin glands. Depending on what they eat, poison dart frogs have a different cocktail of poison in their skin. There is not only epibatidine, but also batrachotoxin and pumiliotoxin. “Around 200 to 300 different poisons are known, and different species of poison dart frogs can store a variety of poisons in the skin,” says Ringler.
With the most poisonous species, just one touch is enough to poison a person. You don’t need an open wound; a slight abrasion or injury is enough. As poison dart frogs’ natural predators, attackers also poison themselves through the mucous membranes, especially in the mouth. Then when a predator bites the frog.
The poison was used by the indigenous peoples, primarily in Colombia, who grazed their arrows over the skin of the frogs in order to shoot them at prey with blowguns. This is where the name poison dart frog comes from. An animal hit is paralyzed or killed within seconds.
Despite everything, the poison dart frogs still have predators. Over the course of evolution, various birds, spiders and snakes have developed mechanisms through mutations that make them insensitive to the poison.
There are 300 species of poison dart frogs.Image: www.imago-images.de
Ringler’s research aims to show what exciting lifestyles the over 300 poison dart frog species have. These frogs exhibit an amazing range of complex behaviors such as brood care, spatial learning and territoriality. Unfortunately, many poison dart frogs are endangered due to habitat loss and climate change.
University professor Ringler says she is always asked why the frogs don’t poison themselves with their poison. One of the reasons is changes in the molecular processes, such as those of the receptor molecules, to which the toxins normally bind. In frogs, the binding sites, i.e. the receptors, have been changed so that they do not poison themselves with the deadly toxin. (aargauerzeitung.ch)