Triethylphosphine gold: cellular uptake and disposition after single and repeated oral doses in rats

The tissue and subcellular pharmacokinetics of gold following single and repeated oral doses of triethylphosphine gold (auranofin) has been studied in rats. After a single dose, the tissue and subcellular gold levels were 5-10 times lower than those reached with injectable gold compounds. In the liver tissues, gold concentrations peaked within 24 h followed by a biphasic clearance, with an initial rapid phase (t1/2 32 h) and a slow terminal phase (t 1/2 11 days). Renal gold concentrations continued to increase for 3 to 5 days and then decreased exponentially with a first order t 1/2 of about 7 days. Intracellularly, between 60-80% of hepatic and 50-70% of renal gold was present in the cytosol. In rats given repeated doses of auranofin, the hepatic and renal gold concentrations were 3-5 times higher than those measured after a single dose. The proportion of cellular gold present in the cytosol was markedly lower, with 43% in the liver and 30% in kidney tissues. In both the liver and kidney, gold concentrations were dose-dependent, whereas in the gastrointestinal tissues the increases as a function of dose were minimal.