Tiopronin (N-[2-mercaptopropionyl] glycin) in rheumatoid arthritis.

Two controlled trials have demonstrated that tiopronin, a new sulfhydryl compound, is active as a slow-acting antirheumatic drug in rheumatoid arthritis. One trial compared 10 patients receiving placebos and 20 receiving tiopronin, 1 gm/day; the second compared two groups of 16 patients who received either placebos or tiopronin, 1.5 gm/day. In addition, 80 patients (56 from the 2 trials plus 24 other patients) were followed up for a long period. Dropout rate for intolerance or inefficacy was comparable to that fund with D-penicillamine. Secondary toxic reactions resembled those of other sulfhydryl compounds.