Risk of Drug Interactions on the Rise as MS Treatments Evolve

This post originally appeared on MedScape.

NATIONAL HARBOR, MD – How often do patients with multiple sclerosis (MS) end up taking drugs that could dangerously interact with other medications they’re taking? A new German study provides a disturbing hint, a pharmacist who spoke at the annual meeting of the Consortium of Multiple Sclerosis Centers told colleagues: Out of 627 patients who took an average of 5.3 drugs each, about 1 in 25 faced a potentially severe interaction, and nearly two-thirds had at least one potentially risky interaction.

It’s crucial to “work on identifying those interactions,” said Jenelle H. Montgomery, PharmD, of Duke University Hospital, Durham, N.C., and to understand the risks. As she noted, interactions don’t just put patients at risk of adverse effects and hospitalization. They can also lead to secondary comorbidities and therapeutic failures.

Newer Versus Older Drugs

Drug interactions in MS have become more common as disease-modifying therapies have evolved, she said. Some older drugs – such as glatiramer acetate, beta-interferons, and fumarates – have low interaction profiles. But newer drugs have more drug interactions caused in part by their side-effect profiles, oral routes of administration, and immunosuppressive instead of immunomodulatory effects, she said. Teriflunomide, for example, interacts with rosuvastatin and warfarin.

S1P modulators are especially complex on the interaction front, Montgomery said. Cardiology consults are recommended for patients taking siponimod, ozanimod, and ponesimod, and there are a number of potential interactions between these drugs and other medications.

In regard to other MS drugs, other medications can disrupt the metabolism of cladribine, she said, and the manufacturer recommends separating any other oral drug doses by 3 hours. Even MS-related drugs can interact: carbamazepine, used to treat MS-related neuropathic pain, interacts with drugs such as siponimod.

Who Is Most at Risk?

How can medical professionals prevent harmful drug interactions in MS? One strategy could be to focus on patients who may be more susceptible. Montgomery highlighted the kinds of patients who were most at risk of polypharmacy, per the 2022 German study: older people, those with lower education levels, and those with more disability. And she pointed out that 77% of all drug interactions were between prescription drugs. Another 19% were between prescription drugs and over-the-counter medications, and 4% were between OTC drugs.

She also emphasized the importance of asking about everything that a patient is taking, including herbal supplements, as nearly 60% of people aged 20 and over take them, and about 75% of those over 60. A quarter of people over age 60 take at least four supplements.

Information about interactions with supplements isn’t always available, she said, but she did mention concerns about St. John’s wort interactions with siponimod and cladribine.

Montgomery also offered several tips: Periodically ask patients to bring in medication bottles or pillboxes; encourage annual checkups with primary physicians; and use drug resources such as Facts and Comparisons, Lexicomp, Clinical Pharmacology, Micromedex, and Natural Medicines.

Disclosures for Montgomery were not available.

This article originally appeared on, part of the Medscape Professional Network.

This post originally appeared on MedScape.