In this narrative review, we analyze pre-registration and post-marketing data concerning hepatotoxicity of all disease-modifying therapies (DMTs) available for the treatment of relapsing-remitting multiple sclerosis, including beta interferon, glatiramer acetate, fingolimod, teriflunomide, dimethyl fumarate, cladribine, natalizumab, alemtuzumab, and ocrelizumab. We review the proposed causal mechanisms described in the literature and we also address issues like use of DMTs in patients with viral hepatitis or liver cirrhosis. Most data emerged in the post-marketing phase by reports to national pharmacovigilance agencies and published case reports or case series. Serious liver adverse events are rare, but exact incidence is largely unknown, as are predictive factors. Unfortunately, none of the DMTs currently available for the treatment of multiple sclerosis is free of potential hepatic toxic effects. Cases of acute liver failure have been reported for beta-interferon, fingolimod, natalizumab, alemtuzumab, and ocrelizumab by different mechanisms (idiosyncratic reaction, autoimmune hepatitis, or viral reactivation). Patients with multiple sclerosis should be informed about possible hepatic side effects of their treatment. Most cases of liver injury are idiosyncratic and unpredictable. The specific monitoring schedule for each DMT has been reviewed and the clinician should be ready to recognize clinical symptoms suggestive for liver injury. Not all DMTs are indicated in cirrhotic patients. For some DMTs, screening for hepatitis B virus and hepatitis C virus is required before starting treatment and a monitoring or antiviral prophylaxis schedule has been established. Beta interferon, glatiramer acetate, natalizumab, and alemtuzumab are relatively contraindicated in autoimmune hepatitis due to the risk of disease exacerbation.

Recent studies estimated an incidence of 4–25% of disease rebound after withdrawal of fingolimod (FTY) for any reason, but specific data on disease reactivation after FTY withdrawal due to pregnancy are limited. The aim of the study was to evaluate the frequency and predictors of disease reactivation in patients who stopped FTY for pregnancy. A multicentre retrospective cohort study was conducted in four Italian MS centres in 2013–2019. Both planned and unplanned pregnancies were included. The annualized relapse rate (ARR) was calculated before FTY treatment, during FTY treatment, during pregnancy and during the year after delivery. In total, 27 patients (mean age 29 years) were included. The ARR 1 year before FTY treatment was 1.3. Patients were exposed to FTY for a median of 2.9 years. The ARR was 0.04 during the last year before conception (p < 0.001 compared with the ARR before FTY treatment). Eleven patients became pregnant after a mean of 88 days following FTY discontinuation, whereas 16 patients stopped FTY after pregnancy confirmation. Relapses were observed in 22% of patients during pregnancy and in 44% in the postpartum period. ARR increased both during pregnancy (0.49; p = 0.027) and in the first year after delivery (0.67; p < 0.001) compared to the last year before pregnancy. Compared with radiological assessment before pregnancy, more patients showed new or enlarging T2 lesions (63% vs 30%; p = 0.02) and gadolinium-enhancing lesions (44% vs 0; p = 0.0001) on brain Magnetic Resonance Imaging. Relapses during pregnancy were the only significant predictor for postpartum relapses (OR 1.9, 95% CI 1.11–3.1). One case of spontaneous abortion and no cases of abnormal foetal development were observed. Despite adequate and prolonged control of disease activity, women who discontinue FTY because of pregnancy are at risk for disease reactivation. In patients who relapsed during pregnancy, the initiation of high-efficacy disease modifying drugs (DMDs) soon after delivery is advisable to prevent postpartum relapses.