Metabolism and distribution of gold compounds.

The pharmacokinetics of gold in blood and urine are compared during intramuscular and oral chrysotherapy for rheumatoid arthritis. Blood gold levels are 3 to 10 fold higher with injectable aurothioglucose and gold sodium thiomalate (50 mg/week) than with oral auranofin (6 mg/day). But, the serum half-life of the parenteral compounds is significantly shorter (5.5 days) than the oral agent (14-21 days). The gold content of urine is nearly 10 times higher with the intramuscular compounds than with the oral drug. The excretory pathways and tissue distribution of gold during conventional intramuscular chrysotherapy are reviewed. Forty percent of a 50 mg injection of gold sodium thiomalate is excreted in 7 days, of which 70% is recovered in the urine. Highest gold concentrations are found in the reticuloendothelial system, adrenal glands and kidneys, while the bone marrow, liver, skin and bone contain the greatest quantities of gold.