Dear Dr. Roach: I am 69 years old and have multiple sclerosis, for which I have been taking Aubagio (teriflunomide) for five months. My monthly liver tests have been negative so far. I am concerned about the long-term effects of this drug on my liver. Can the drug damage the liver permanently over time? Also, what are the symptoms of a damaged liver? What is the liver’s function? Thank you for your help. — C.D.S.

Answer: Multiple sclerosis is a disease in which the coating of nerve cells, called myelin, is destroyed by the body’s immune and inflammatory systems. Symptoms of this nerve damage include numbness, weakness and vision changes. Most people with MS have symptoms that relapse and then remit.

Teriflunomide blocks some of the actions of T lymphocytes, and this has been shown to reduce the relapse rate by about 30% and decrease the progression of disability. As you point out, teriflunomide can adversely affect the liver.

While 10% to 13% of people will show abnormal liver enzymes on a blood test, damage to the liver is uncommon. Most cases occur in the first six months after beginning treatment, so blood testing is recommended to evaluate any adverse effects on the liver. Initially there are no symptoms, which is why blood testing is recommended. By the time symptoms have developed, there is usually extensive liver damage.

Most people will not experience any ill effects of the liver, which is good, because the liver has countless functions related to making proteins that regulate most body functions, as well as detoxifying drugs and metabolic byproducts. Stopping teriflunomine caused improvement in the reported cases of liver toxicity.