Interaction of D-penicillamine with gold salts: in vivo studies on gold chelation and in vitro studies on protein binding.

Serum and urinary gold levels were monitored in 18 patients previously treated with gold salts for rheumatoid arthritis and the effects of D-penicillamine studied. There was no statistically significant change in urinary gold levels on D-penicillamine therapy although there were some individual variations. Serum gold levels fell during D-penicillamine therapy but the rates of fall did not differ from those seen in patients not treated. In vitro studies on protein binding of gold salts suggest that a high affinity exists between gold salts and albumin with low levels of unbound gold even at concentrations far exceeding those seen in vivo. These preliminary results suggest that at therapeutic levels only small amounts of gold are available for chelation by penicillamine. It is concluded that penicillamine at low dosage is an unreliable chelator of gold salts in vivo and its use in the management of gold toxicity remains speculative.