Written by Maureen McNulty
Medically reviewed by Luc Jasmin, M.D., Ph.D., FRCS (C), FACS
- 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:
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