Biological action of colorless and yellow solutions of gold sodium thiomalate on thrombin activity and the mixed lymphocyte reaction.

Gold sodium thiomalate is a pale yellow powder which forms a colorless solution when added to sterile water. The marketed form of gold sodium thiomalate is a pale yellow solution. The yellow color develops as a result of the sterilization process. This study demonstrates that the physical change induced in the drug by the sterilization process has no effect on the action of gold sodium thiomalate on the serine esterase thrombin, nor on the inhibition of the mixed lymphocyte response. Thus it is unlikely that the yellow component is responsible for benefit in rheumatoid arthritis. If the components creating the yellow color cause toxicity, the preparation and/or formulation of the drug should be changed.