Pharmacokinetics of gold sodium thiomalate in rabbits

Male, New Zealand white rabbits (3.5-4.3 kg) received a single 2-mg/kg dose of gold sodium thiomalate (Myochrysine) via intramuscular (N = 4) and intravenous (N = 3) routes. Blood samples were drawn from the marginal ear vein for a period of 5-10 days. The concentration of gold in whole blood was determined using graphite furnace atomic absorption spectrophotometry. The blood concentration-time profiles obtained following both routes of administration were best described by a two-compartment open model with first-order absorption for the intramuscular route. Gold was absorbed rapidly with a mean (harmonic) absorption half-life of 9.0 min, with a peak concentration of 6.0 +/- 1.0 micrograms/ml (N = 4). Blood concentrations declined in a biphasic manner; the mean alpha half-lives were 0.738 and 1.78 hr for the iv and im routes, respectively. The corresponding terminal (beta) half-lives were 54.1 and 63.0 hr. The estimated volume of the central compartment (70 to 93 ml/kg) agreed closely with the rabbit blood volume. The mean (+/- SD) extent of the dose absorbed following intramuscular injection was 68.9 +/- 12.4%.