Proresid therapy in rheumatoid arthritis. A comparison with injectable gold using life-table analysis.

Proresid, mainly consisting of podophyllotoxin derivatives and two glycosides thereof, has been used as a disease-modifying antirheumatic drug in Sweden since the late 1960s. A life-table analysis of Proresid treatment averaging 41 months (range 4-144) in 79 rheumatoid arthritis patients showed a termination rate of 40, 56, 75 and 85% after 1/2, 1, 2 and 4 years, respectively. Dominant reasons for discontinuing therapy were inefficacy (37%) and gastrointestinal symptoms (35%). The risk of discontinuation of therapy due to inefficacy was constant over time, while the risk due to other causes, including side effects, gradually decreased. A comparison with injectable gold therapy showed, after adjusting for confounding factors, that the total termination incidence was higher (p < 0.05) in the Proresid-treated patients. A comparison with the regional cancer register of 334 patients exposed to Proresid for a mean time of 2.2 years showed no increased cancer risk after a mean observation time of 6.1 years.