Succimer found ineffective for removing mercury
Some families have turned to a drug used for treating lead poisoning as an alternative therapy for treating autism. NIH researchers say new data offers little support for this practice.
Balintfy: Succimer is a drug used for treating lead poisoning in children. Dr. Walter Rogan, a senior investigator in the epidemiology branch at the National Institute of Environmental Health Sciences, says the drug has been studied and is approved by the Food and Drug Administration to reduce lead in the blood of children.
Rogan: Back in the 90ís we had done a large scale clinical trial of the drug to treat lower level lead exposure in children in the hopes of reversing the IQ deficit that comes from exposure to lead.
Balintfy: Dr. Rogan explains that about 780 kids participated in the clinical trial — which included taking blood samples — and that they were followed for five years.
Rogan: And although we decreased their blood leads by about 40% in the short term, we weren't able to have any effect on their IQ.
Balintfy: Dr. Rogan reports that although succimer is not approved by the FDA to reduce mercury, in the belief that conditions like autism and autism spectrum disorders are caused, in part, by mercury poisoning, some families are turning to the drug as an alternate therapy.
Rogan: It is a kind of a general purpose metal chelator. By which I mean it makes metals that you stored in your body more soluble in urine.
Balintfy: With blood samples left over from that earlier lead trial, researchers were able to analyze them for mercury. Although researchers found that succimer lowered blood concentrations of mercury after one week, continued therapy for five months only slowed the rate at which the children accumulated mercury.
Rogan: So itís not as effective a chelator for mercury as it is for lead.
Balintfy: Dr. Rogan emphasizes that while succimer reduced lead levels by about 40%, it lowered mercury levels by less than 20%. He adds that the practice of using succimer for conditions like autism is not supported by data.
Rogan: We hear stories, newspaper reports, websites that say itís used in kids with autism and autism spectrum disorders. And there is some belief that those disorders may have something to do with mercury exposure. And so if you're contemplating using this drug for any reason that has anything to do with mercury, the take-home message form this is in a large formal trial, itís not very effective at lowering blood mercury.
Balintfy: Most mercury exposure in the United States is from methylmercury, found in foods such as certain fish. Thimerosal, a preservative once more commonly used in vaccines, contains another form of mercury, called ethylmercury. For more information on studies of succimer, visit www.niehs.nih.gov. For information on autism and autism spectrum disorders, visit www.nimh.nih.gov. This is Joe Balintfy, National Institutes of Health, Bethesda, Maryland.