Arsenic distribution in rabbits after Lewisite administration and treatment with British anti-Lewisite (BAL)

The standard treatment of Lewisite (dichloro(2-chlorovinyl)arsine) poisoning is by chelation with BAL (British anti-Lewisite, dimercaptopropanol). The present study investigated the effect of BAL treatment on the distribution of arsenic after Lewisite administration. Lewisite was administered subcutaneously at the LD10 and LD40 of the compound. Without BAL treatment arsenic was eliminated with a half-life in blood of between 55 and 75 hr and a blood clearance of 120 ml/hr/kg. Arsenic had a large volume of distribution of several liters per kilogram, indicating extensive distribution in tissues. The highest tissue concentrations, more than seven times blood concentrations, were found in the liver, lung, and kidneys. These organs maintained an approximately constant concentration ratio with blood during the sampling period. Concentrations in tissues with a blood-to-tissue barrier, such as the brain and the spinal cord, rose between 4 and 96 hr while blood concentrations declined more than fourfold over the same time period. BAL treatment by four equal, maximally tolerated doses over 12 hr substantially reduced arsenic concentrations in blood and tissues. For example, at 24 hr the concentrations in brain and liver (target organs for arsenic toxicity) were reduced by 65 to 89% over the range of Lewisite doses administered. The total exposure of brain and spinal cord was reduced by more than two-thirds by BAL treatment. Further, the blood clearance of arsenic was increased. BAL treatment enhanced the elimination of arsenic in two ways: by decreasing the tissue-to-blood partitioning which mobilizes arsenic into the blood stream, and by increasing the clearance of arsenic.