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Starting an S1P Receptor Modulator: What To Expect

Posted on July 23, 2021
Medically reviewed by
Evelyn O. Berman, M.D.
Article written by
Brooke Dulka, Ph.D.

  • Before starting a sphingosine-1-phosphate (S1P) receptor modulator for relapsing forms of MS, your doctor will likely order certain blood tests, an electrocardiogram, and an eye exam.
  • S1P receptor modulators are oral drugs taken every day, and it is important to stay on schedule.
  • While you are taking an S1P receptor modulator, your doctor may monitor your health for any changes. Report all side effects to your doctor right away.

A newer class of disease-modifying therapies (DMTs) known as sphingosine-1-phosphate receptor modulators have a unique mechanism of action that makes them particularly useful for treating relapsing forms of multiple sclerosis. For those considering taking an S1P receptor modulator, it can be helpful to know what to expect.

Which S1P Receptor Modulators Are Available?

There are now several S1P receptor modulators approved by the U.S. Food and Drug Administration (FDA) to treat MS. Drugs in this category include:

More S1P receptor modulators are currently being studied for their potential safety and efficacy in treating relapsing forms of MS.

Read What Are the Relapsing Forms of MS?

Tests Before Starting S1P Receptor Modulators for MS

Before starting an S1P receptor modulator, your neurologist will likely order specific tests. These will check for any abnormalities that may make S1P modulators less safe for you to take. The Cleveland Clinic recommends that, prior to starting treatment with an S1P modulator such as Mayzent, you should consider all of the tests below.

Electrocardiogram

In a small portion of individuals who have taken S1P modulators, bradycardia (slowing of the heart rate) can occur. An electrocardiogram (EKG), performed by attaching wires to the skin, can confirm that you have a normal heart rhythm and electrical activity.

Ophthalmic Evaluation

A thorough eye exam can screen for macular edema, a type of swelling. Macular edema is a rare complication associated with S1P receptor modulator treatment.

CYP2C9 Genotype

CYP2C9 is a protein involved in the body’s metabolization and processing of drugs. A person’s genetic pattern for this protein, obtained via a blood test, determines the titration and dosage of an S1P receptor modulator. People with some genotypes should not take S1P receptor modulators at all, so the results from this test may indicate you are not a good candidate for a drug in this category.

Complete Blood Count

A complete blood count, or CBC, is a common blood test that can screen for many problems, including infections and blood cell disorders. The Cleveland Clinic recommends individuals with MS do not start an S1P receptor modulator if they have any active infections.

Liver Function Tests

Liver function tests, performed using blood samples, determine whether your liver is working properly. S1P receptor modulators are metabolized by the liver.

Varicella Zoster Antibody Testing

The varicella zoster virus causes chickenpox and shingles. If your blood tests negative for the antibodies associated with varicella zoster, your doctor may recommend you be vaccinated against this virus prior to starting treatment with an S1P receptor modulator.

Starting and Staying on a Schedule

If you are switching from an injected drug you take once a week (or less frequently) to an oral drug taken daily, there are some steps to help with this transition. Consider the following strategies to stay on schedule with a daily medication:

  • Set alarms to remind you to take each dose.
  • Use pillboxes that separate pills by day of the week and even morning and evening doses.
  • Leave medication in plain sight so it is harder to forget about taking it.
  • Stick to a daily routine where medication is taken at the same times as other specific activities.

For S1P receptor modulators and other disease-modifying therapies to be effective, they must be taken at the correct dosage and frequency, every time, as directed.

Side Effects of S1P Receptor Modulators

S1P receptor modulators are generally considered to be relatively safe and well tolerated. Common side effects differ between specific S1P receptor modulators, but can include:

  • Headache
  • Hypertension (high blood pressure)
  • Respiratory infections
  • Urinary tract infections
  • Back pain

As a class, S1P receptor modulators have been associated with rare but potentially serious side effects. These include:

  • Cardiac events, such as bradycardia
  • Macular edema, a buildup of fluid within the eye

Your doctor may recommend monitoring when first starting an S1P receptor modulator if you have a history of myocardial infarction (heart attack), heart failure, or bradycardia. Otherwise, monitoring may not be required. Whenever you start a new medication, it is important to report all side effects to your doctor right away.

Read What Are S1P Receptor Modulators?

Talk With Others Who Understand

MyMSTeam is the social network for people with multiple sclerosis and their loved ones. On MyMSteam, more than 170,000 members come together to ask questions, give advice, and share their stories with others who understand life with multiple sclerosis.

Are you taking an S1P receptor modulator for your MS? Share your experience in the comments below, or start a conversation by posting on your Activities page.

All updates must be accompanied by text or a picture.
Evelyn O. Berman, M.D. is a neurology and pediatric specialist and treats disorders of the brain in children. Review provided by VeriMed Healthcare Network. Learn more about her here.
Brooke Dulka, Ph.D. is a freelance science writer and editor. She received her doctoral training in biological psychology at the University of Tennessee. Learn more about her here.

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