The relationship of sulfoxidation status to efficacy and toxicity of penicillamine in the treatment of rheumatoid arthritis.

Penicillamine shows some structural similarities to carbocysteine. The ability to oxidize carbocysteine, i.e., the sulfoxidation status, shows a bimodal distribution in the general population. In this study, sulfoxidation status was determined in 50 of 60 rheumatoid arthritis patients receiving penicillamine. We found that poor sulfoxidation status, compared with good sulfoxidation status, was associated with a 3.9 times higher incidence of toxicity.