The effects of elevated blood lead levels and succimer chelation therapy on physical growth in developing rhesus monkeys

Seventy-two female rhesus monkeys were randomly assigned to three lead expo sure conditions (none, birth to 1 year, birth to 2 years). In a completely crossed design, the lead-exposed and control monkeys were randomized to pla cebo or chelation therapy which began at 1 year of age. Dosing was conducte d daily beginning on day 8 postpartum. The lead dose levels were adjusted b iweekly to gradually elevate the blood lead level of each monkey to a targe t of 1.69-1.93 mu mol/L (35-40 mug/dL). Succimer (or placebo) was administe red orally (30 mg/kg/day for 5 days and 20 mg/kg/day for 14 additional days ) for a total 19-day treatment regimen. There were two separate chelation r egimes at 53 and 65 weeks of age. Succimer therapy in combination with lead abatement reduced blood lead levels significantly faster than lead abateme nt alone; however, that advantage disappeared once succimer therapy was dis continued. Weight, crown-rump length, and head circumference were measured regularly. Growth in weight, length, and head circumference did not vary si gnificantly as a function of blood lead levels. Succimer chelation therapy did not significantly affect weight, length, or head circumference through 2 years of age. (C) 2001 Academic Press.