Leflunomide Mech of action:- This immunomodulator inhibits proliferation of stimulated lymphocytes in patients with active RA. Ahritic symptoms are suppressed and radiological progression of disease is retarded. Leflunomide is rapidly conveed in the body to an active metabolite which inhibits dihydro-orotate dehydrogenase and pyrimidine synthesis in actively dividing cells. Antibody production by B-cells may be depressed. The active metabolite has a long t 1/2 of 2-3 weeks. Adverse effects:- Include diarrhoea, headache, nausea, rashes, loss of hair, thrombocytopenia, leucopenia, increased chances of chest infection and raised hepatic transaminases. It is not to be used in children and pregnant/ lactating women. Ref:- kd tripathi; pg num:-212