• If you have multiple sclerosis (MS) and want to switch treatments, you may need to wait for one disease-modifying therapy (DMT) to clear out of your system before you start another.
• This “wash-out period” may be a different length of time depending on which DMT you were taking, which DMT you are switching to, and your personal health factors.
• Your doctor can help you figure out whether you need to go through a wash-out period and how long it should last.

Many people with MS switch DMTs at least once — if not many times — throughout their treatment. When switching from one medication to another, doctors may recommend a “wash-out period” in which you stop taking one drug and wait for a designated period of time before starting another.

Wash-out periods come with risks and benefits. Continue reading to learn about eight things to consider when planning for a wash-out period.

1. Wash-Out Periods Are Common

If you are living with MS, you will likely consider undergoing a medication change at some point.

In one study in which more than 110,000 people with MS tried nearly 270,000 DMTs, researchers found that these medications were discontinued about 68.2 percent of the time during the first two years of treatment. You might stop taking a DMT if:

• It’s not effective enough at controlling your MS.
• 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 are 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.
• You can’t afford the medication.
• You don’t need the medication — for example, in patients 70 years of age or older, with no evidence of acute disease for two years or longer.

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

Read more about signs it may be time to switch DMTs.

2. Wash-Out Periods May Help Prevent Side Effects

The main purpose of a wash-out 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 are fully cleared away, so if you take one DMT one day and a different DMT the next, both medications may be still be in your body at the same time. This could cause the drugs to interact or create worse side effects than usual.

3. The Risk of Flares May Rise During Wash-Out Periods

A major downside of going through a wash-out period is that your MS may not be completely under control and may flare up. For people with relapsing forms of MS including relapsing-remitting MS, clinically isolated syndrome, and active secondary progressive MS, flares are periods of new or worsening symptoms.

Your doctor may recommend regular follow-up testing during a wash-out period to look for early signs of flares. They may measure your levels of lymphocytes (white blood cells) or use an MRI to look for lesions (areas of your nervous system that show damage).

If you experience flares during a wash-out period, you may be able to take other medications such as intravenous (through a vein) steroids. These other treatments may help control symptoms until your new DMT takes effect.

Once you start taking a new DMT after a wash-out period, it will take some time for the new drug to start fully 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 Wash-Out Periods

In many cases, researchers have not conducted clinical trials to specifically calculate how long a wash-out period should be. However, experts have shared general guidelines for different DMTs based on how these medications affect the body:

• Glatiramer acetate (Copaxone), rituximab (Rituxan), or interferons — Often, no wash-out period is needed
• Fingolimod (Gilenya) or siponimod (Mayzent) — No wash-out period, or a wash-out period of a few weeks if your blood sugar levels are low
• Dimethyl fumarate (Tecfidera) — No wash-out period unless you have lymphopenia (low levels of lymphocytes)
• Natalizumab (Tysabri) — One to three months
• Ocrelizumab (Ocrevus) — Zero to three months
• Mitoxantrone (Novantrone) — Three to six months
• Cladribine (Mavenclad) or alemtuzumab (Lemtrada) — Wash-out period lasts until you have active disease (signs of MS reappear)

For medications that work by binding to the cell receptor CD20, such as ofatumumab (Kesimpta), some experts recommend skipping a wash-out period. Minimizing the time between the stopping the older drug and starting the newer drug may help prevent MS from becoming more active.

Medications like teriflunomide (Aubagio) may take up to two years to be cleared out of your body. However, your doctor may speed up this process by prescribing medications such as cholestyramine (Prevalite) or activated charcoal for 11 days.

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

5. Wash-Out Periods Can Vary From Person to Person

Other factors can also help determine how long your wash-out period is.

When deciding on the length of your wash-out period, your doctor may also consider how active your MS is, your other health conditions, and your reason for switching DMTs.

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

6. Your Doctor May Suggest Tapering

Most of the research and guidelines surrounding MS wash-out periods assume that people will stop taking a DMT all at once. However, some doctors may suggest that you taper off a drug by gradually decreasing your dose over time.

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

7. There Are Other Situations When You May Need Wash-Out Periods

You may also need to undergo a wash-out period if you want to become pregnant. There haven’t been many studies about whether certain DMTs are safe to use during pregnancy or whether they can harm a developing baby. Therefore, experts usually recommend that those who want to get pregnant go through a wash-out period before they conceive.

How long the wash-out period should last depends on the DMT, although your doctor may also make other recommendations. Some recommended guidelines state:

• Interferon beta — Can be used throughout pregnancy
• Interferon, glatiramer acetate, natalizumab — No wash-out period needed; use up until you find out you are pregnant
• Teriflunomide — Stop using two to four months before you plan to get pregnant
• Dimethyl fumarate and fingolimod — Go through a two-month wash-out period before pregnancy
• Alemtuzumab — Avoid this medication four months before you want to become pregnant

In some cases, your doctor may also suggest a wash-out 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 a 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 health care team. There are many approved DMTs for MS, and your neurologist can help you switch to a different treatment option that works better for your needs. Your doctor can also help recommend a wash-out period that will keep you safe while minimizing your risk of MS flares.

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 multiple sclerosis.

Have you gone through a wash-out period? What were your experiences? Share in the comments below, or start a conversation by posting on MyMSTeam.