Study aim: To assess the effect of Sylimarin versus placebo on the reduction of liver complication of Teriflunomide in patients with multiple sclerosis Design: This is a double-blind randomized clinical trial with control group, phase III, in which eligible patients will be randomly assigned through the drawing of lots to the intervention and control groups. This trial will be double-blinded. Settings and conduct: This study will be performed in the Neshat Clinic in Hamadan city on 42 eligible patients with multiple sclerosis. The patients will be randomly assigned to the intervention and control groups through the drawing of lots. This trial will be double-blinded. Participants/Inclusion and exclusion criteria: Inclusion criteria: Age 18 to 70 years Multiple sclerosis Exclusion criteria: Pregnancy or breastfeeding Alcohol consumption Active viral hepatitis or chronic liver disease Intervention groups: Intervention group: Triflunomide tablet 14 mg daily plus silymarin tablet 140 mg twice daily for 2 months Control group: Triflunomide tablet 14 mg daily plus placebo tablet (starch) twice a day for 2 months Main outcome variables: Primary outcome: Liver and biliary function tests (including AST, ALT, ALP, bilirubin and GGT)