Kesimpta Drug Interactions: What You Need to Know

When you're taking a medication that modifies your immune system, knowing what else you can and can't take is essential. Kesimpta (Ofatumumab) doesn't have a long list of traditional drug-drug interactions like many oral medications do — it won't interact with your blood pressure pill or your antidepressant. But because it depletes B cells and suppresses immune function, the interactions it does have are important to understand.

How Drug Interactions Work With Kesimpta

Most drug interactions you hear about involve medications competing for the same enzymes in the liver (the cytochrome P450 system). Kesimpta doesn't work that way. It's a monoclonal antibody — a large protein that's broken down by the body's normal protein degradation pathways, not by liver enzymes.

Instead, Kesimpta's interactions are primarily pharmacodynamic, meaning they involve additive or overlapping effects on the immune system. The main concern is combining Kesimpta with anything else that suppresses immunity, or using vaccines that require a functioning immune system to be safe and effective.

Medications That Interact With Kesimpta

Major Interactions

1. Live and Live-Attenuated Vaccines

This is the most important interaction. Do not receive live vaccines during Kesimpta treatment. Because Kesimpta depletes B cells, your immune system may not be able to control a live vaccine virus, potentially leading to the very infection the vaccine is meant to prevent.

Examples of live vaccines to avoid:

• MMR (measles, mumps, rubella)
• Varicella (chickenpox)
• Yellow fever
• Live influenza (FluMist nasal spray)
• BCG (tuberculosis)
• Live shingles vaccine (Zostavax) — note: Shingrix, the recombinant shingles vaccine, is NOT live and may be given

Timing: Complete all live vaccinations at least 4 weeks before starting Kesimpta.

2. Other Immunosuppressive Therapies

Using Kesimpta alongside or shortly after other immunosuppressant medications significantly increases the risk of serious infections. This includes:

• Other anti-CD20 therapies — Ocrevus (Ocrelizumab), Rituxan (Rituximab). Switching between these requires careful washout periods.
• Other MS disease-modifying therapies — Gilenya (Fingolimod), Mayzent (Siponimod), Lemtrada (Alemtuzumab), and others that suppress immune function.
• Non-MS immunosuppressants — Azathioprine, Methotrexate, Mycophenolate, Cyclophosphamide.

When switching from another MS therapy to Kesimpta, your neurologist will determine an appropriate washout period based on the half-life and mechanism of the previous drug.

Moderate Interactions

3. Inactivated Vaccines

Inactivated vaccines (such as the flu shot, COVID-19 vaccines, pneumococcal vaccines, and tetanus) are safe to receive during Kesimpta treatment. However, they may be less effective because your B cells — which help generate antibody responses to vaccines — are depleted.

Timing: When possible, complete inactivated vaccinations at least 2 weeks before starting Kesimpta for the best immune response.

4. Corticosteroids

Short courses of corticosteroids (like Methylprednisolone for an MS relapse) are commonly used alongside Kesimpta and are generally considered safe. However, prolonged corticosteroid use adds to the immunosuppressive burden, increasing infection risk. Discuss the duration and necessity with your doctor.

Supplements and Over-the-Counter Medications to Watch

Kesimpta has no known significant interactions with common OTC medications like acetaminophen, ibuprofen, or antihistamines. However, keep these points in mind:

• Immune-boosting supplements (echinacea, elderberry, high-dose vitamin C) — While not dangerous, these are designed to stimulate the immune system, which can theoretically work at cross-purposes with a B-cell depleting therapy. There's no strong evidence of harm, but discuss with your doctor if you take them regularly.
• Vitamin D — Often recommended for MS patients regardless of treatment. No interaction with Kesimpta. Many neurologists encourage supplementation.
• Probiotics — Generally safe. No known interaction with Kesimpta.
• NSAIDs (ibuprofen, naproxen) — Safe to take as needed. No interaction.

Food and Drink Interactions

Good news: Kesimpta has no known food or drink interactions. You don't need to avoid any foods, and moderate alcohol consumption does not directly interact with the medication. That said, alcohol can suppress immune function on its own, so moderation is wise when you're already on an immunosuppressive therapy.

What to Tell Your Doctor

Before starting Kesimpta — and at every follow-up — make sure your doctor knows about:

• All medications you're taking, including prescription, OTC, vitamins, and supplements
• Any recent vaccinations or upcoming vaccine plans
• Previous immunosuppressive treatments, especially other MS therapies, and when you stopped them
• Current or recent infections — even minor ones like a cold or UTI
• History of hepatitis B — mandatory screening before starting Kesimpta (see our side effects guide)
• Pregnancy plans — contraception is required during treatment and for 6 months after the last dose

A helpful tip: Bring a complete, written medication list to every appointment. Include dosages and how long you've been taking each one.

Final Thoughts

Kesimpta's drug interaction profile is relatively simple compared to many medications. The key concerns are live vaccines (don't get them during treatment) and other immunosuppressants (don't stack them without careful medical oversight). Beyond that, it plays well with most medications and has no food restrictions.

If you're planning to start Kesimpta, work with your neurologist to get your vaccinations up to date and review your medication list before your first dose. For more on the treatment itself, check out our guides on what Kesimpta is and how it works. And if you need help finding it, Medfinder is here to help.