• Switching disease-modifying therapies (DMTs) is common among people who are treating relapsing forms of multiple sclerosis (MS).
• Neurologists may recommend switching DMTs if your MS shows signs of progression, you have frequent MS flares, or your risk of serious side effects increases.
• The decision to switch DMTs is best made through the collaborative process of shared decision-making between you and your doctor.

Effective treatment of MS involves disease-modifying therapies. DMTs are approved by the U.S. Food and Drug Administration (FDA) based on their proven ability to slow disease processes in MS. Switching DMTs is common among people with relapsing forms of MS. In a large observational study spanning 19 years, researchers followed 110,326 people diagnosed with relapsing-remitting MS. The study found that participants stopped one DMT and switched to another within six months 159,309 times.

There are several reasons you and your neurologist may decide to switch your MS treatment from one DMT to another, including side effects, disease progression, and a medication’s reduced effectiveness over time.

Why Do DMTs for MS Sometimes Stop Working?

Researchers have suggested several reasons why some treatments may stop working after a while. One of the most common theories is that your body may gradually develop antibodies against the disease-modifying drugs. Normally, your body makes immune proteins called antibodies against foreign invaders like bacteria and viruses. When you take MS medication, your immune system may recognize it as foreign and make antibodies to deactivate the drug, preventing it from working properly. People taking interferons or alemtuzumab (Lemtrada) are at higher risk of developing such antibodies.

Allowing Time for a DMT To Take Effect

Generally, before considering a treatment switch, doctors wait until enough time has passed to allow a DMT to fully take effect — on average, at least one year. That’s usually long enough to monitor the response to a new treatment with magnetic resonance imaging (MRI) or other scans and watch for worsening symptoms. It’s important to continue taking your current medication exactly as directed to make sure it works as effectively as possible.

Signs It May Be Time To Consider Switching DMTs

Neurologists treating MS will look for factors such as the following — any of these could indicate that it might be time to discuss switching medications.

1. Return of MS Relapses and Symptoms

You may be treating your MS as directed but still experiencing signs of breakthrough disease. These include:

• Ongoing relapses (flares) in the case of relapsing-remitting multiple sclerosis (RRMS), clinically isolated syndrome (CIS), or active secondary-progressive MS
• Continued disease activity (persistent or worsening symptoms)
• New or worsening brain lesions on MRI scans

These may be signs it is time to consider different treatment options.

2. Increased Risk of Serious Side Effects

MS is an autoimmune disease — your immune system attacks your body, causing MS symptoms. DMTs work by discouraging your immune system from damaging your tissues. At the same time, weakening your immune system in this way may put you at risk of opportunistic infections that would have not otherwise been an issue. The good news is that DMTs are becoming safer, and the incidence of infections is lower with newer DMTs.

Progressive Multifocal Leukoencephalopathy

One of the most serious conditions associated with infection is progressive multifocal leukoencephalopathy (PML). This happens when a common, usually harmless virus called the John Cunningham (JC) virus attacks the myelin that insulates your brain cells, causing disability or even death. Normally, the JC virus is contained by your immune system. In a person whose immune system is weakened by MS medications, the JC virus poses more danger.

PML is very rare, even among people taking DMTs, but all FDA-approved MS treatments still include a black box warning about the risk.

3. Disease Progression

Neurologists have many ways to track disease activity and measure the effectiveness of DMTs. These tools include disability progression scales like the Expanded Disability Status Scale and assessments of quality of life. A doctor will also consider imaging, such as MRI scans of the central nervous system (brain and spinal cord), to look for enlarging or new lesions. MS activity visible on MRI scans usually correlates closely with MS disease progression overall.

Transition to Secondary Progressive MS

Most people with MS are initially diagnosed with relapsing-remitting MS, or RRMS, which is characterized by flares of symptoms with periods of relative recovery in between. However, many people with RRMS may progress to secondary progressive MS (SPMS), in which some symptoms stick around after each episode and disability accumulates. Progression to SPMS early in your disease course could be a sign that your current treatment may not be effective.

Shared Decision-Making and Switching DMTs

Treatment decisions are made in collaboration with your health care team. This process of considering your experiences and preferences along with your doctor’s expertise is called shared decision-making. It has been shown to improve the health outcomes of people living with MS.

Make sure you regularly follow up with your neurologist and attend any other scheduled appointments. Your doctors need to see how your MS is progressing. By getting the necessary tests and scans, you help your doctors determine if your current disease-modifying treatment is working effectively, so any decision to change MS treatment is well informed.

No one knows your MS symptoms better than you. Make sure to let your health care providers know about any problems and complications you may have.

If you’re considering switching MS treatments, read about washout periods and when they may be needed.

Talk With Others Who Understand

MyMSTeam is the social network for people with multiple sclerosis and their loved ones. On MyMSTeam, more than 195,000 members come together to ask questions, give advice, and share their stories with others who understand life with MS.

Do you have questions about switching medications for MS? Have you and your doctor discussed a treatment change? Share your questions and experiences in the comments below, or start a conversation on your Activities page.