Clinical efficacy and adverse effects of tiopronin in rheumatoid arthritis. Report of a follow-up in 50 patients.

A follow-up of 15.4 months has been carried out in 50 patients suffering from classical or definite rheumatoid arthritis, treated with tiopronin, a new slow acting sulphydrylant agent. The attention was focused mainly on the frequency of the major side effects needing withdrawal of the drug in 20% of the patients; in other 20% of the cases we have observed the disappearance of the major side effects after reduction of the tiopronin dosage. The most important major side effect was renal toxicity. Five cases of proteinuria and among these four cases of nephrotic syndrome were recorded. These side effects disappeared 2-5 weeks after withdrawal of the tiopronin. From a clinical point of view a positive response was observed in 56% and a complete lack of efficacy in 22% of patients. The clinical benefit and a panel of side effects very close to those of D-penicillamine were confirmed.