Living with multiple sclerosis (MS) often involves managing the condition with disease-modifying therapies (DMTs). These treatments are essential for slowing MS progression and reducing how often relapses occur.

Many people with MS also use additional medications to address symptoms like pain, fatigue, and muscle spasms. However, taking multiple medications increases the risk of drug interactions, which may worsen MS symptoms or lead to other harmful side effects. In this article, we’ll cover eight classes of drugs that may require careful monitoring by your doctor or even avoidance when you’re on DMTs. We’ll also explain why it’s important to talk to your health care provider before changing any medications.

1. Steroids

Steroids such as prednisone and dexamethasone are commonly prescribed during MS relapses to reduce inflammation. However, when combined with certain DMTs, they can come with additional risks. In particular, combining steroids with biologics like natalizumab (Tysabri) or fingolimod (Gilenya) can raise the risk of infections, especially if taken in high doses or for long periods.

Immune Suppression

When both steroids and DMTs weaken the immune system, the risk of infections increases. For example, DMTs like fingolimod already reduce the immune system’s ability to fight infections, and adding steroids can further raise this risk.

Worsening Side Effects

Using steroids for a long time can cause complications such as osteoporosis, high blood pressure, and diabetes, which make managing MS even more difficult.

If you need steroids for an MS relapse, your doctor will usually prescribe them for a short time and monitor you for any signs of infection. This approach helps balance the benefits with reducing the risks.

2. Antidepressants

Antidepressants are often prescribed to help manage depression and anxiety in people with MS. However, some types may make MS symptoms worse or lead to other health risks.

Fracture Risk

Some people with MS have low bone density, making them more likely to fracture a bone. Antidepressants, especially selective serotonin reuptake inhibitors (SSRIs) and tricyclic antidepressants (TCAs), can add to this risk by contributing to bone loss. If your DMT already affects your physical stability, combining it with an antidepressant can raise the risk of falls and, thus, fractures.

Sexual Dysfunction

Sexual dysfunction, such as erectile dysfunction or vaginal dryness, is common in people with MS. Certain antidepressants, including serotonin and norepinephrine reuptake inhibitors (SNRIs), SSRIs, and TCAs, can worsen these issues and further affect sexual health.

Bladder and Bowel Issues

Some antidepressants, such as duloxetine, may help manage bladder symptoms, but others — particularly TCAs — can make bladder and bowel issues worse. Problems such as constipation or urinary retention (difficulty emptying the bladder) are already common in advanced MS and may be aggravated by certain antidepressants.

Seizure Risk

Certain antidepressants, including bupropion and TCAs, may increase seizure risk at high doses or in people who are already prone to seizures.

3. Nonsteroidal Anti-Inflammatory Drugs

Nonsteroidal anti-Inflammatory drugs (NSAIDs), such as ibuprofen (Advil, Motrin) and naproxen (Aleve), are often used to help ease pain, inflammation, and flu-like symptoms that can occur with some MS treatments. However, NSAIDs should be used with caution when taken with certain DMTs.

Liver Damage

Certain DMTs, like fingolimod, can put stress on the liver, and adding NSAIDs can increase the risk of liver damage. While NSAIDs have long been known to affect the kidneys, long-term use can also raise the risk of liver damage, particularly in people already at risk of liver problems.

Digestive Tract Issues

Prolonged use of NSAIDs can lead to digestive tract complications, such as ulcers or bleeding. This is a particular concern for people with MS who may already experience digestive issues.

4. Anti-Seizure Drugs

Medications such as gabapentin (Neurontin) and pregabalin (Lyrica) are often prescribed to manage neuropathic pain in MS. However, these medications can have some downsides.

Sedation and Drowsiness

Anti-seizure drugs can cause significant drowsiness, which can worsen the fatigue many people with MS already experience. Some DMTs may also contribute to extreme tiredness, making it even harder to stay alert and carry out daily activities.

Impaired Balance

Many people with MS already experience balance issues, and anti-seizure drugs can further increase the risk of falls by affecting coordination.

5. Anticholinergics

Anticholinergic medications, such as oxybutynin and tolterodine, are often used to manage bladder dysfunction, a common issue for people with MS. However, these drugs can also cause several unwanted side effects.

Memory Problems and Confusion

Anticholinergics can lead to trouble with memory and confusion, which can especially be a problem for people with MS who may already have cognitive symptoms (problems with thinking and processing information). If you’re on a DMT that also causes cognitive issues, taking these medications could make these challenges even harder to manage.

6. Muscle Relaxants

Muscle relaxants, such as baclofen and tizanidine, are often prescribed to reduce muscle spasticity (feelings of stiffness and muscle spasms) in people with MS. However, these medications can cause significant side effects, particularly when combined with DMTs.

Fatigue and Weakness

Muscle relaxants can make you feel more tired and weak, which may worsen the muscle weakness and fatigue people with MS, especially those on DMTs, often experience.

Balance Issues

These drugs can affect coordination, increasing the risk of falls. This is especially dangerous if MS or your DMT already makes maintaining balance hard.

7. Antihistamines

Antihistamines, such as diphenhydramine (Benadryl) and cetirizine (Zyrtec), are commonly used to manage allergies. However, these drugs can also make some MS-related symptoms worse.

Drowsiness and Dizziness

Some antihistamines cause drowsiness and dizziness, which may worsen fatigue and balance issues related to MS and its treatment. If you’re also taking DMTs that can cause dizziness, such as interferon beta-1a (Avonex, Rebif), the combination can make it even harder to stay alert and steady on your feet.

Cognitive Impairment

Some antihistamines may cause poor memory and concentration, making it harder for people with MS to manage their cognitive symptoms.

8. Wakefulness-Promoting Drugs

Fatigue is one of the most common and challenging symptoms for people with MS, so certain medications may be recommended to help. If, after careful assessment by your doctor, excessive daytime sleepiness is also found, wakefulness-promoting drugs like modafinil (Provigil) and armodafinil (Nuvigil) might be an option. Although these medications can be effective, their use should be carefully considered for people taking DMTs.

Cardiovascular Side Effects

Adding wakefulness-promoting drugs could increase cardiovascular (heart and blood vessel) side effects for people taking DMTs like fingolimod. Modafinil is known to increase heart rate and blood pressure, which could make problems worse if you’re already managing heart-related symptoms from DMTs.

Sleep Disturbances

Modafinil can help manage daytime fatigue, but it may also cause nighttime sleep disturbances, including insomnia. Many DMTs, such as interferons, already carry the risk of disrupting sleep. Combining wakefulness-promoting drugs with these treatments could worsen overall sleep quality, leaving you more fatigued in the long term.

Keep Your Medical Team Informed

Managing MS can be complex, so it's important to keep open communication with your entire health care team. Make sure your neurologist, pharmacist, and other specialists know about all the medications and supplements you're taking. Regular medication reviews are key to avoiding harmful drug interactions, particularly when new treatments are introduced or symptoms change. Your health care providers can help evaluate the potential risks of each drug and suggest adjustments or alternatives to minimize side effects and keep you feeling your best.

Regular Reviews

Your medication list should be reviewed frequently, especially if you start or stop any treatments. Keep an updated list of your medications with you at all times. Your doctor may recommend cutting down on unnecessary medications to lower the risk of drug interactions or side effects.

Complete Transparency

Be sure to mention all over-the-counter medications, including herbal and nutritional supplements, because these can also interact with prescribed medications. This is particularly important when taking DMTs, as even seemingly harmless supplements can have significant effects.

By working closely with your health care team and keeping them informed about all the medications you take, you can lower the risk of drug interactions and ensure that your treatment plan is optimized for managing your MS.

Talk With Others Who Understand

MyMSTeam is the social network for people with MS and their loved ones. On MyMSTeam, more than 216,000 members come together to ask questions, give advice, and share their stories with others who understand life with MS.

Are you taking any of these medications to manage MS symptoms? Have you and your doctor or pharmacist discussed any drugs that you should avoid? Share your experience in the comments below, or start a conversation by posting on your Activities page.