NIH Study: Succimer found ineffective for removing mercury

[Guest guest]

There are some questions on this study regarding methodology, outcomes,

and relevance to autism but FYI.

http://www.nih.gov/news/health/oct2010/niehs-22.htm

DHHS, NIH News

National Institute of Environmental Health Sciences (NIEHS)

For Immediate Release Friday, October 22, 2010

Contact: Robin Mackar, NIEHS 919-541-0073

Succimer found ineffective for removing mercury

Succimer, a drug used for treating lead poisoning, does not effectively

remove mercury from the body, according to research supported by the

National Institutes of Health. Some families have turned to succimer as

an alternative therapy for treating autism.

" Succimer is effective for treating children with lead poisoning, but it

does not work very well for mercury, " said Walter Rogan, M.D., head of

the Pediatric Epidemiology Group at the National Institute of

Environmental Health Sciences (NIEHS), part of NIH, and an author on the

paper that appears online in the Journal of Pediatrics.

" Although it is not approved by the Food and Drug Administration to

reduce mercury, succimer is reportedly being used for conditions like

autism, in the belief that these conditions are caused, in part, by

mercury poisoning, " Rogan stated. " Our new data offers little support

for this practice. "

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. The safety of higher

doses and longer courses of treatment has not been studied.

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.

To conduct the study, the researchers used samples and data from an

earlier clinical trial, led by NIEHS, called the Treatment of

Lead-exposed Children (TLC) trial. In the TLC study, succimer lowered

blood lead in 2-year-old children with moderate to high blood lead

concentrations.

Using blood samples from 767 children who participated in the TLC trial,

the researchers measured mercury concentration in the toddlers’ blood

samples collected before treatment began, one week after beginning

treatment with succimer or placebo, and then again after three

month-long courses of treatment. Mercury concentrations were similar in

all children before treatment. Concentrations eventually increased in

both groups, but more slowly in the children given succimer. Succimer

had produced a 42 percent difference in blood lead, but only an 18

percent difference in blood mercury.

" Although succimer may slow the increase in blood mercury

concentrations, such small changes seem unlikely to produce any clinical

benefit, " Rogan said. He and his colleagues had reported in an earlier

paper that succimer has few adverse side effects, mostly rashes, and an

unexplained increase in injuries in children given succimer rather than

placebo.

The subjects of the study did not have unusually high blood mercury

concentrations for African-American children and the study did not

investigate where the mercury in the children came from.

" This research fills a gap in the scientific literature that could not

be addressed any other way. We were fortunate to have samples already

collected from toddlers who had been treated with succimer for lead

poisoning allowing us to help answer this important question, " said

Birnbaum, Ph.D., director of NIEHS and the National Toxicology

Program.

Birnbaum noted NIH's commitment to supporting research that provides

critically needed information that will help drive more prevention and

treatment options for children with autism and other neurodevelopmental

disorders.

The study was supported by the NIEHS Intramural Research Program, the

National Institute for Minority Health and Health Disparities at NIH,

and the National Center for Environmental Health at the Centers for

Disease Control and Prevention. The succimer, Chemet, and the placebo,

were gifts from McNeil Laboratories, Fort Washington, Pa.

The NIEHS supports research to understand the effects of the environment

on human health and is part of NIH. For more information on

environmental health topics, visit www.niehs.nih.gov. Subscribe to one

or more of the NIEHS news lists

(www.niehs.nih.gov/news/releases/newslist/index.cfm) to stay current on

NIEHS news, press releases, grant opportunities, training, events, and

publications.

The National Institutes of Health (NIH) — The Nation's Medical Research

Agency — includes 27 Institutes and Centers and is a component of the

U.S. Department of Health and Human Services. It is the primary federal

agency for conducting and supporting basic, clinical and translational

medical research, and it investigates the causes, treatments, and cures

for both common and rare diseases. For more information about NIH and

its programs, visit www.nih.gov.

Reference: Cao Y, Chen A, RL, Radcliffe J, Dietrich KN, Caldwell

KL, et al. 2010. Efficacy of Succimer Chelation of Mercury at Background

Exposures in Toddlers: A Randomized Trial. J Pediatr. Epub ahead of

print. DOI:10.1016/j.jpeds.2010.08.036.