[8] Penicillamine can be used as a disease-modifying antirheumatic drug (DMARD) to treat severe active rheumatoid arthritis in patients who have failed to respond to an adequate trial of conventional therapy,[9] although it is rarely used today due to availability of TNF inhibitors and other agents, such as tocilizumab and tofacitinib.

Common side effects include rash, loss of appetite, nausea, diarrhea, and low white blood cell levels.

[1] Bone marrow suppression, dysgeusia, anorexia, vomiting, and diarrhea are the most common side effects, occurring in ~20–30% of the patients treated with penicillamine.

[10][11] Other possible adverse effects include: Penicillamine is a trifunctional organic compound, consisting of a thiol, an amine, and a carboxylic acid.

[22] He had discovered the compound in the urine of patients (including himself) who had taken penicillin, and experimentally confirmed that it increased urinary copper excretion by chelation.

He had initial difficulty convincing several world experts of the time (Denny-Brown and Cumings) of its efficacy, as they held that Wilson's disease was not primarily a problem of copper homeostasis but of amino acid metabolism, and that dimercaprol should be used as a chelator.