Charcoal may be a cheap and effective medicine for certain types of cardiac poisoning, research suggests.
Yellow oleander seeds are poisonous
Scientists focused on the use of charcoal to treat the effects of eating oleander seeds - a common problem in Sri Lanka.
But they believe the same treatment may also be effective at neutralising drugs used in Western populations that can produce a similar effect.
Deliberate self-poisoning with yellow oleander seeds is common in Sri Lanka, causing around 2,000 deaths every year.
Swallowing the seeds has a severe effect on the heart - and results in death in about 10% of cases.
Multiple-dose activated charcoal should be given to all patients who have ingested yellow oleander seeds
It can be treated by fitting a temporary pacemaker, or by the use of antibodies.
But these treatments are expensive, and not widely available in rural areas.
But the study showed that repeated doses of charcoal could be just as effective.
In fact, they reduced the death rate from oleander poisoning by up to 70%.
Oleander seeds are dangerous because they mimic the effects of a group of drugs called the cardiac glycosides.
When used in controlled doses these drugs can help to treat heart failure, and rapid or irregular heartbeat.
But in high doses they can stimulate potentially deadly heart damage.
Charcoal works as a binding agent, encouraging the dangerous chemicals to clump together, so that the digestive system can more easily expel them from the body before they can cause damage.
The study focused on 400 people who were admitted to hospital with oleander poisoning.
Some were given a 50g dose of charcoal four times a day for three days, and others were given sterile water as a dummy treatment. All were given standard forms of treatment too.
The death rate in the placebo group was 8% - but among those who receive charcoal treatment it was just 2.5%.
Charcoal treatment also cut the rate of secondary symptoms, such as life-threatening irregular heart rhythms (arrhythmias).
Lead researcher Dr H J de Silva, from the University of Kelaniya, Sri Lanka, said: "Multiple-dose activated charcoal is safe and effective in reducing death and life-threatening cardiac arrhythmias after yellow oleander poisoning, and should be given to all patients who have ingested yellow oleander seeds.
"Expensive interventions could be reserved for
patients who have dangerous arrhythmias at the time of presentation with poisoning, or those who develop arrhythmias despite treatment with activated charcoal."
Fellow researcher Dr Jeff Aronson said the findings suggested that charcoal would also be of benefit in the treatment of patients who have been poisoned with other cardiac glycosides, such as the drugs digoxin and digitoxin.
It may also help to treat problems with other drugs that are eliminated from the body in a similar fashion.
Activated charcoal is charcoal that has been treated with oxygen to make it more absorbent.
The research is published in The Lancet medical journal.