Changing treatments is quite common for people with multiple sclerosis (MS). Many switch the type of disease-modifying therapy (DMT) they take at least once, if not several times, as they search for what works best for them. You might consider switching from one DMT to another for several reasons. Perhaps side effects from your current DMT are disrupting your quality of life, or maybe you continue to have relapses even after taking the drug for several months.

If you’re considering switching to a new medication, your health care provider may recommend a washout period beforehand.

What Does ‘Drug Washout’ Mean?

In medical terms, a drug washout is the period after you stop taking one medication and before you start a new one. The washout period allows time for the old medication to stop affecting your body so that you can see the full effect of the new medication.

Continue reading to learn about eight facts to consider when planning for a washout period between MS DMTs.

1. Washout Periods for MS DMTs Are Common

If you’re living with MS, you’ll likely consider changing medications at some point. In a 2021 study of more than 110,000 people with MS who’d tried nearly 270,000 DMTs, researchers found that about 68 percent of the time, participants discontinued new treatments within two years of starting them.

The main purpose of a washout period is to help you avoid side effects from multiple medications at once.

You might stop taking a DMT if:

• It’s not controlling your MS well enough.
• Your disability gets worse while using the drug.
• You continue to experience MS relapses while taking the DMT.
• You have too many side effects.
• You’re allergic to the drug.
• You have a hard time sticking to the medication’s schedule or using it as directed.
• Your body starts rejecting the medication.
• It’s too expensive.
• You don’t need the medication — for example, in people aged 70 or older with no evidence of acute disease (sudden illness) for two years or longer.

In these situations, you and your doctor may decide you should stop taking your DMT, undergo a washout period, and then try a new DMT.

2. DMT Washout Periods May Help Prevent Side Effects and Increase Tolerability

While DMTs might be effective in the treatment of multiple sclerosis, the side effects can be difficult to handle. Certain DMTs, such as highly effective DMTs, are sometimes associated with a high risk of side effects. The main purpose of a washout period is to help you avoid experiencing unpleasant side effects from multiple medications at once.

DMTs may stay in your system for a little while before they’re fully cleared away, so if you take a particular DMT one day and a different DMT the next, both medications may be in your body at the same time. This could cause the drugs to interact or lead to worse MS DMT side effects than usual.

3. DMT Washout Periods Might Raise the Risk of Flares

A major downside of going through a washout period is that your MS may not be completely under control and may flare up because you’re not continuing to receive medication. For people with relapsing forms of MS including relapsing-remitting MS (RRMS), clinically isolated syndrome, and active secondary progressive MS, flares are periods of new or worsening symptoms. Flares are caused by inflammation in the central nervous system, which includes the brain and spinal cord.

Your doctor may recommend regular follow-up testing during a washout period to look for early signs of flares. They may measure your levels of lymphocytes (white blood cells) or use a magnetic resonance imaging (MRI) scan to look for lesions — areas of your nervous system that show damage — to compare to your baseline (before you stopped taking the medication).

The length of a washout period may differ depending on the DMTs you’re switching between and your personal health needs.

If you experience flares during a washout period, your doctor may recommend short-term treatment with high-dose corticosteroids to help control your MS symptoms until your new DMT takes effect. Corticosteroids can be taken as pills (oral route) or as an injection into your vein (intravenous route).

Once you start taking a new DMT after a washout period, it will take some time for the new drug to fully begin working. You won’t know how effective the new treatment is until three to six months after you start using it.

4. Different DMTs Require Different Washout Periods

In many cases, researchers haven’t conducted clinical trials to determine just how long a washout period should be. However, health experts have shared general guidelines for different DMTs based on how these medications affect the body:

• Alemtuzumab (Lemtrada) and cladribine (Mavenclad) — The washout period lasts until laboratory monitoring indicates no signs of active disease.
• Dimethyl fumarate (Tecfidera) — No washout period is needed unless laboratory results show lymphopenia (low levels of lymphocytes, a type of white blood cells).
• Fingolimod (Gilenya, Tascenso ODT) and siponimod (Mayzent) — A few weeks’ washout period may be considered if you have low blood sugar levels.
• Glatiramer acetate (Copaxone, Glatopa), rituximab (Rituxan), or interferons — Usually, no washout period is needed.
• Mitoxantrone — Washout period lasts three to six months.
• Natalizumab (Tysabri) — Washout period lasts one to three months.
• Ocrelizumab (Ocrevus) — Washout period lasts zero to three months.

For medications that work by binding to the cell receptor CD20, such as ofatumumab (Kesimpta), some doctors recommend skipping a washout period. However, a washout period may sometimes be necessary, depending on the reason for switching, such as an infection or low levels of immunoglobulins (proteins that help fight infections). Minimizing the time between discontinuation of the older drug and starting the newer one may help prevent MS from becoming more active.

Medications like teriflunomide (Aubagio) may take up to two years to clear out of your body. However, your doctor may speed up this process with a rapid elimination protocol. In this detailed medical plan, medications such as cholestyramine (Prevalite) or activated charcoal are taken for 11 days. The protocol may be used in people who experience severe side effects or are planning to become pregnant.

Your doctor may recommend a longer or shorter washout period based on your health details and their experience and knowledge about a specific DMT.

5. DMT Washout Periods Can Vary From Person to Person

Several other factors can also help determine how long your washout period is. For example, when deciding on the length of your washout period, your doctor may consider:

• How active your MS is
• What other health conditions you have
• Why you’re switching DMTs

Work with your doctor to weigh the risks and benefits of different washout period lengths. Only your doctor — who understands your values and health factors — can help you decide how to approach a washout period.

6. Your Doctor May Suggest Tapering the DMT

Most of the research and guidelines surrounding washout periods for MS DMTs assume that people will stop taking a DMT all at once. However, some doctors may suggest tapering off a drug by gradually decreasing the dose.

Your doctor can advise you on whether it’s better to stop your current DMT all at once or taper off gradually.

One study among people with MS on natalizumab treatment found that those who tapered off were less likely to experience a disease flare. Some experts also suggest tapering off fingolimod. However, researchers haven’t studied tapering before a washout period for most DMTs, so it’s unclear whether this strategy may help reduce relapse rates or lead to a higher risk of flares.

7. Other Situations May Require Washout Periods

You may need to undergo a washout period if you want to become pregnant. Your plan for conception depends on your disease progression and your overall health. Ideally, people with MS should have stable disease activity for six to 12 months before trying to become pregnant.

Randomized controlled trials for DMTs haven’t included pregnant or lactating women, according to the journal Neurology Clinical Practice, so there’s little research regarding whether these medications are safe during pregnancy or may harm a developing baby. Currently, no MS DMTs are approved by the U.S. Food and Drug Administration (FDA) for use in pregnancy or breastfeeding. Therefore, health experts usually recommend that those who want to get pregnant go through a washout period before they try to conceive.

The length of the washout period depends on the DMT, although your doctor may also make other recommendations. Guidelines include the following:

• Alemtuzumab — Avoid this medication four months before you want to become pregnant.
• Dimethyl fumarate — A washout period of at least one week is recommended.
• Fingolimod — A washout period of at least two months is recommended to avoid harm to the baby.
• Glatiramer acetate — No washout period needed, and this drug may be used during pregnancy.
• Interferon-beta — This medication can be used throughout pregnancy, although a two-week washout may be recommended in some cases.
• Natalizumab — A two- to three-month washout period is recommended.
• Ocrelizumab and ofatumumab — A one- to three-month washout period is recommended.
• Teriflunomide — Stop using two to four months before you plan to get pregnant; the rapid elimination protocol is recommended.

In some cases, your doctor may also suggest a washout period if you need to undergo treatment for a different health condition. Talk to your neurologist if you’re not sure whether you should discontinue your DMT.

8. Don’t Change Your Medication Without Talking to Your Doctor

Make sure to take your DMTs as directed. Skipping medication, decreasing your doses, or taking your medication in ways not directed by your doctor can make your MS worse.

If you’re not happy with your DMT for any reason, talk to your neurology care team. Many DMTs are approved for MS, and your neurologist can help you switch to an MS treatment option that works better for you. Your doctor can also help recommend a washout period that will keep you safe while minimizing your risk of MS flares.

Talk With Others Who Understand

MyMSTeam is the online social network for people with multiple sclerosis and their loved ones. On MyMSTeam, more than 217,000 members come together to ask questions, give advice, and share their stories with others who understand life with multiple sclerosis.

Have you gone through a washout period? What was your experience? Share in the comments below, or start a conversation by posting on your Activities page.