Pharmacokinetics of auranofin in animals.

Gold from orally administered auranofin (AF) was absorbed 17-23% in rats and 15-38% in dogs. Gold was highly bound to blood cells and plasma proteins. Gold terminal half life was 1.2-1.8 days in rat blood and plasma (measured for 7 days post dose) and 19.5 days in the dog (measured for 42 days). Excretion of gold (rat and dog) was via feces (84 and 81%) urine (10 and 16%) and bile (3% of dose). Rat tissue levels of gold were highest in the kidney. Evidence indicated that AF was rapidly degraded to triethylphosphine oxide with the remaining molecular fragments postulated to be a protein-gold complex and acetylthioglucose.