A snakebite ointment identified by Australians

Leave it to the Australians, people who live fang to foot with the world’s deadliest snakes, to find a way to use an ointment for the pain of anal fissures against snakebites instead. Dirk Van Helden of the University of Newcastle in Australia had the idea that fast-moving venom of some snakes might hit a molecular roadblock from such an ointment. The idea worked, and van Helden and colleagues published their findings in the June 26, 2011, issue of Nature Medicine in an open-access paper.

Why turn to an ointment for anal fissures? The ointment contains nitroglycerin, or glyceryl trinitrate. It’s got good old nitric oxide in it, the stuff that’s probably now best known for its role in curing erectile dysfunction, relaxing blood vessels in a certain area so that they can more easily become…congested. In excruciating anal fissures, nitric oxide relaxes blood vessels, reducing pain. Nitric oxide also happens to interfere with fluid transport in the lymphatic system.

Some—but not all—snakes inject venom with molecules so large, they can’t enter the bloodstream via the tiny capillaries around the bite. Instead, they rely on the larger passageways of the lymphatic system. Australia boasts…if that’s the right word…a lot of snakes that make venom like that. Take, for example, the brown snake. In spite of its almost colorless name, it happens to be one of the deadliest snakes in the world. Getting medical help within minutes of a bite is literally the difference between life and death.

That anal fissure ointment may help buy more of those minutes. Based on the work of van Helden’s group, applying the ointment within seconds of the bite can double the time until symptoms appear. In people, the researchers only measured the traveling time of a harmless, radiolabeled fluid to mimic snake venom. Application of the ointment considerably extended the time it took the fluid to travel from the foot to the groin, from less than a half hour to almost an hour. In snakebite minutes, that can mean a lifetime.

They also turned to rats and real venom to test the idea further. Again, applying ointment within seconds of venom exposure slowed down the venom’s course through the rat, adding an extra 30 minutes to the time before symptoms appeared.

All of this is great for snake-risky people who live in Australia, where snakes produce lymphatic-loving venom in abundance. But for others around the world at risk of snakebite, say, from a cobra or a black mamba (!), the fissure cream is less likely to help, as their venom less helpfully contains small molecules that don’t need the lymph system to get where they’re going.

That said, Dirk Van Helden and the other authors recommend trying the nitric oxide ointment approach with other kinds of venoms to see if its benefits might go beyond brown snake bites. Alternatively, one could just avoid Oz or brown snakes altogether.

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