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Oral Succimer Decreases the Gastrointestinal Absorption of Lead in Juvenile Monkeys
John D. Cremin, Jr., Melissa L. Luck, Nellie K. Laughlin and Donald R. Smith
Environmental Health Perspectives
Vol. 109, No. 6 (Jun., 2001), pp. 613-619
Published by: The National Institute of Environmental Health Sciences
Stable URL: http://www.jstor.org/stable/3455036
Page Count: 7
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Although succimer (Chemet, meso-2,3-dimercaptosuccinic acid, DMSA) is considered to be a safe and effective chelating agent for the treatment of lead poisoning in humans, there is concern that it may increase the gastrointestinal (GI) absorption and retention of Pb from exposures suffered concurrent with treatment. This concern is justified because the availability of Pb-safe housing during outpatient treatment with oral succimer is limited. We used a juvenile nonhuman primate model of moderate childhood Pb intoxication and a sensitive double stable Pb isotope tracer methodology to determine whether oral succimer chelation affects the GI absorption and wholebody retention of Pb. Infant rhesus monkeys (n = 17) were exposed to Pb daily for 1 year post-partum to reach and maintain a target blood lead (BPb) level of 35-40 μg/dL. Animals were administered succimer (n = 9) or vehicle (n = 8) over two successive 19 day succimer treatment regimens beginning at 53 and 65 weeks of age. The present study was conducted over the second chelation regimen only. Animals received a single intravenous (iv) dose of stable 204 Pb tracer (5 μg, 24.5 nmol) followed by a single oral dose of stable 206 Pb tracer (72.6 μg, 352 nmol) immediately before chelation, in order to specifically evaluate GI Pb absorption and whole-body Pb retention with treatment. We collected complete urine and fecal samples over the first 5 days and whole blood over the first 8 days of treatment for analyses of stable Pb isotopes using magnetic sector inductively-coupled plasma mass spectrometry. Results indicate that succimer significantly reduced the GI absorption of Pb (vehicle, 64.9% ± 5.5; succimer, 37.0% ± 5.8; mean ± SEM). Succimer also significantly increased the urinary excretion of endogenous Pb by approximately 4-fold over the vehicle treatment, while endogenous fecal Pb excretion was decreased by approximately 33%. Finally, although succimer reduced the whole-body retention of endogenous Pb by approximately 10% compared to vehicle, the majority (77%) of the administered internal dose of Pb tracer was retained in the body when assessed after 5 days of treatment. These data do not support the concern that succimer treatment increases GI Pb absorption.
Environmental Health Perspectives © 2001 The National Institute of Environmental Health Sciences