The effect of levamisole on adjuvant arthritis in the rat.

Levamisole (LEV), an immunostimulatory agent, was studied for its effect on adjuvant disease of the rat. The drug was administered continuously according to three schedules: (a) seven days prior to immunization with complete Freund's adjuvant (CFA); (b) simultaneously with CFA; or (c) 14 days after CFA. Control animals received CFA alone, LEV alone, or were sham treated with saline. Three weekly evaluations were made, recording the general condition, weight curves, joint scores, and volume of hind paws. Whole body radiographs were made at the end of six weeks. In all experimental groups, LEV accentuated the severity of the disease as compared to animals receiving CFA alone. Within the experimental groups, an increased severity was observed with earlier administration of LEV, although the day of disease onset was not altered. Spinal involvement was less severe with each consecutive administration of LEV. These findings suggest that LEV is effective not only in restoring an impaired cellular immune response, but also in enhancing an already activated system. It seems however, that for this stimulation the timetable of LEV administration is crucial, and that continuous therapy may result in a loss of efficiency.