Dapsone in rheumatoid arthritis

Dapsone, a synthetic sulfone with chemical similarities to sulfapyridine, has been used for a number of years to treat leprosy and dermatitis herpetiformis. Recently, a number of prospective, randomized, double-blind trials have shown their success in the management of rheumatoid arthritis, with dapsone being superior to placebo and comparable to chloroquine and hydroxychloroquine. Its mode of anti-inflammatory actions in rheumatoid arthritis is not clearly understood, but modulation of neutrophil activity or inhibition of neutrophil inflammatory product formation or release appear to play a role. The major limiting side effect is hemolytic anemia, which may be mitigated through careful patient selection, conservative drug dosing, close monitoring, and possibly, concurrent administration of antioxidants or cytochrome P450 inhibitors. Methemoglobinemia is another common finding among patients receiving dapsone therapy, but rarely does it result in prominent symptoms other than transient pallor. Less common adverse events to dapsone include the idiosyncratic reactions of leukopenia and agranulocytosis, cutaneous eruptions, peripheral neuropathy, psychosis, toxic hepatitis, cholestatic jaundice, nephrotic syndrome, renal papillary necrosis, severe hypoalbuminemia without proteinuria, an infectious mononucleosis-like syndrome, and minor neurological and gastrointestinal complaints. In this report, two patients with advanced rheumatoid arthritis, who were safely and effectively treated with dapsone after failure with other second-line agents, are described and the literature is reviewed. We suggest that dapsone is an effective second-line agent in the treatment of rheumatoid arthritis.