By Janet Fang
Posting in Science
A topical ointment, containing compounds commonly used for chest pain, can help you survive an otherwise fatal snakebite.
My closest brush with death was almost exactly 5 years ago, shortly after sunset in the Chiricahua Mountains in Arizona. After coming upon snake roadkill, I got out of the car to stare at it, as you do. With my face less than a foot away, the Western Diamond-backed Rattlesnake (Crotalus atrox) coiled into its strike pose, hissing and rattling bloody murder. (Allegedly I continued screaming for another minute after getting back into the car, that is, before coming out again to take that dark, blurry photo.)
Make no mistake, it was a total field biologist fail, but admittedly, it would have been slightly poetic… Fang dies from fangs.
Last week, scientists revealed that a drug for heart failure could significantly improve the survival time of snakebite sufferers by delaying the toxin.
Worldwide, about 100,000 people a year die from snakebites, which also accounts for 400,000 amputations. From the bite site, bulky toxin molecules in venom get into the blood and heart through the vessels in our lymphatic system. Delaying this transit could mean the difference between dying on the road… or not.
The recommended first aid for a bite includes tightly wrapping the bitten limb to shut the lymphatic vessels – but this has led to gangrene and doesn’t really work if you’re bitten on the face or torso.
So, a team led by Dirk van Helden of the University of Newcastle in Australia looked for a pharmacological first aid approach.
They found that when rats are injected with a fatal dose of snake venom, their survival time increased by 50% if they immediately received an ointment containing glyceryl trinitrate – which slowed down the venom’s spread in their lymphatic vessels, killing them in 96 minutes vs. 65.
The compound is better known as nitroglycerin, used to treat everything from tennis elbow to angina, ScienceNOW explains. It releases nitric oxide (NO) in through the skin, causing the lymphatic vessels to clench.
To see if the ointment could buy humans time to find antivenom, the team injected people in the foot with a radioactive tracer:
- In those who didn’t receive the ointment, the tracer took 13 minutes to climb to the top of the leg to the groin.
- For those who smeared the cream on within a minute, the tracer’s transport was detained by 54 minutes.
"It gives you time and a half to get help," says van Helden. "I'd prefer that to just time."
The team conducted its experiments using "particularly nasty" venom from the Eastern Brown Snake (Pseudonaja textilis, pictured), "one of the most toxic things in the world," says van Helden. But unfortunately, as Science News points out, you might be out of luck if you're bitten by the (more cinematic) Black Mamba or cobra, since the ointment isn’t effective against venom with smaller toxic molecules that can enter the bloodstream directly.
The study was published in Nature Medicine last week.
Images: brown snake by Stewart Macdonald via Flickr, rattlesnake by Janet Fang
Jul 4, 2011