Getting a diagnosis of multiple sclerosis (MS) is a life-changing experience. However, there have been major breakthroughs in MS treatment: In 1993, the U.S. Food and Drug Administration (FDA) approved the first medication that can actually slow down the progression of the disease. Before that, doctors could only treat MS symptoms. There are now 12 of these disease-modifying drugs. Disease-modifying drugs can reduce the frequency of MS attacks, reduce damage to the brain and spinal cord, and reduce the chances of becoming disabled. There is a disease-modifying drug for every type of MS, and recently a new drug was approved by the FDA to treat primary progressive MS, a rare form of MS that does not have periods of remission. MS is caused by an abnormal immune system (your body's defense system), which means your body mistakenly targets the tissues of your brain and spinal cord. Immune system cells cross into your central nervous system and attack the myelin, or protective lining around nerves. Over time the myelin sheaths around your nerves deteriorate and become scarred, and nerve signals become blocked or distorted. Disease-modifying drugs work by interfering with this abnormal immune system response. Disease-modifying drugs are the best treatment available for MS. The one you'll take depends on your level of disease, your response to the drug, and your side effects. (You can't take any of the drugs if you are pregnant or planning to become pregnant.) You may choose one drug over another based on how the drug is given and its known risk factors. This is a decision you will need to make with your MS healthcare provider. Here's a look at the 12 approved drugs. Betaseron (interferon beta-1b) was the first drug approved for MS, in 1993. Interferon drugs are proteins that alter the immune system. This drug is given by injection under the skin every other day. Betaseron is approved for people who are newly diagnosed with MS and for people who have relapsing MS. If you use this drug, you will need to inject yourself or have someone inject you at bedtime. The drug comes in a preloaded syringe. Flu-like symptoms are common after the injection. These symptoms may be reduced over time as you continue to use the drug. Taking over-the-counter pain relief, like acetaminophen (Tylenol) or ibuprofen (Advil), at the time of your injection may lessen this reaction. You can also have skin reactions at the injection site, so you will need to rotate the areas of injection. Liver abnormalities, depression, low white blood cell counts, and allergic reactions are less common risk factors. Avonex (interferon beta-1a) is an interferon drug that was approved for MS in 1996. Avonex is injected into a muscle once a week. Avonex is used to treat newly diagnosed and relapsing MS. This drug also comes in a preloaded syringe to be injected at bedtime. Avonex may cause flu-like symptoms after injection. Less common side effects are depression, liver abnormalities, allergic reactions, and heart problems. Rebif (interferon beta-1a) was approved in 2002 and is injected under the skin three times a week. It is approved for people with relapsing forms of MS. Side effects are similar to Betaseron. Extavia (interferon beta-1b) is the most recently approved interferon drug. It is given by injection under the skin every other day. It is approved for new and relapsing MS. Side effects are similar to Betaseron. Copaxone (glatiramer acetate) was approved in 1996. It is given by injection under the skin every day. Copaxone is not an interferon drug. It works by blocking the damage MS does to myelin nerve sheaths. Copaxone can be used to treat new or relapsing cases of MS. It can cause a reaction at the injection site, so these areas need to be rotated. Uncommon side effects are chest pain, anxiety, and flushing. Novantrone (mitoxantrone) is an anticancer drug that works against MS by suppressing immune system cells. It is a drug with serious side effects and is only used for worsening relapsing or relapsing and progressing MS. It is given four times per year as an intravenous infusion (given directly into your vein at a medical facility). It was approved in 2000. It can only be used for two to three years. Side effects include fatigue, bruising, infections, hair thinning, and nausea. Serious liver damage and heart damage are possible. Tysabri (natalizumab) is a synthetic (produced in a lab) antibody that blocks immune system cells from getting into the central nervous system. Approved in 2006, it is given once a month by intravenous infusion. It is used for relapsing MS in people who have not had a good response to other disease-modifying drugs. Tysabri can have side effects, such as fatigue and allergic reactions. The main reason it is reserved for people who have not done well with other medications is because it can also cause a very rare side effect called progressive multifocal leukoencephalopathy, which is a virus-based brain infection that is often fatal. Gilenya (fingolimod) was approved in 2010, and it is the first MS disease-modifying drug available as a pill–you take one every day. It can be used for relapsing MS. Side effects may include headache, muscle ache, and diarrhea. Less common side effects include infections and eye swelling. Gilenya is a new type of drug that blocks white blood cells from crossing into the central nervous system. Tecfidera (dimethyl fumarate/BG-12) is a disease-modifying drug approved in 2013. It works two ways: protecting the nerves while quieting the immune system. Studies of MS patients taking this twice-daily pill have shown reduced relapse rates, fewer new brain lesions, and a lower overall rate of disability progression. The most common side effects are flushing and gastrointestinal symptoms, including diarrhea, nausea, and abdominal pain. Treatment may lower white blood cell counts, which means that people taking Tecfidera need routine lab studies. Aubagio (teriflunomide) is a once-daily oral disease-modifying drug typically used for relapsing MS. It can reduce the number of MS lesions and delay MS progression. The most common reported side effects are diarrhea, nausea, hair thinning, and elevated liver enzymes. There are two serious precautions with Aubagio. Those with liver problems should not take this drug. Also, due to a high risk of birth defects, both men and women trying to conceive should not take this medication. Lemtrada (alemtuzumab) is a monoclonal antibody that selectively depletes the autoimmune cells that lead to MS nerve damage. It is given by IV infusion. Data from randomized trials show that alemtuzumab is more effective than interferon beta-1a for reducing the relapse rate in relapsing-remitting MS. There is a small increased risk of potentially serious infections and autoimmune disorders, including immune thrombocytopenia (ITP). Alemtuzumab is reserved for folks who have a poor response to other drugs. Ocrevus (ocrelizumab), the newest drug to treat MS, came to the scene in 2017. A monoclonal antibody, it's the first drug ever approved to treat primary progressive MS, one of the most debilitating forms of the disease. It also treats relapsing-remitting MS. The drug works by targeting B-cells, which are immune cells thought to play a role in damaging myelin and nerves. In clinical trials, ocrelizumab significantly slowed disability progression and reduced brain lesions, and for patients with relapsing MS, the drug reduced yearly relapses by half. Ocrelizumab is given every six months by IV infusion and common side effects include reactions at the infusion site and upper respiratory tract infections. In clinical trials, all disease-modifying drugs have been shown to effectively slow down the progression of MS. But not all people have the same results. One drug might work for you and another might not. You may also have more side effects with one drug than another. That's why you'll need to work closely with your MS care provider to find the drug that works best for you with the most tolerable side effects. Most MS experts agree that the sooner you start taking an MS disease-modifying drug, the less likely it is that you'll develop the kind of brain or spinal cord damage that leads to disability. No matter what drug you choose now, you may decide to switch to a new drug in the future. There are several drugs being tested now that may be approved in the next few years. These include more options to take in pill form and drugs with fewer side effects. The future for MS treatment has never been brighter. Key Takeaways Disease-modifying drugs have changed the way MS is treated. They are the first MS drugs that can slow down the progression of the disease. The drug you take depends on which type of MS you have, your response to the drug, the side effects you can tolerate, and how you prefer the drug to be given. Work closely with your care provider to find the right drug for you. The sooner you start taking a disease-modifying drug, the better your chances are of limiting the damaging effects of MS.