Rat arthritis was induced by bovine type II collagen. To present the remedial effects on type II collagen arthritis and clinical efficacy, a high dose of methotrexate, of a level similar to that used in cancer patients was given to rats.

Healthy male Brown Norway rats were used, of mean weight; 300 g. There were 7 subgroups: a control group, given collagen only, an orally methotrexate treated (2.5mg/week), high methotrexate dose groups; 10 mg/kg, 30 mg/kg, 50 mg/kg, 100 mg/kg and a low dose methotrexate group (0.375 mg/kg/week, 4 times) were included in the present study. Type II collagen was injected for arthritis induction and a single intraperitoneal injection of methotrexate was administered after 15 days. Orally treated group was administered 4 times (2.5 mg/week). Histopathologic findings were evaluated.

50 mg/kg methotrexate was effectively reduced the arthritis index and significantly decreased inflammatory cell number between 2nd and 6 weeks.

A high dose of methotrexate may be clinically effective in the short period treatment of rheumatoid arthritis patients.