Polypharmacy and Potential Drug-Drug Interactions: Monitor Patients With Multiple Sclerosis


Pharmacists should review the medications of patients with multiple sclerosis regularly to assess drug-drug interactions.

Patients with multiple sclerosis (MS) are prone to polypharmacy (PP) and are at risk for at least 1 potential drug-drug interaction (pDDI), according to the results of a study published in the Journal of Pharmaceutics.1

MS is a progressive and debilitating medical condition. Because of its complexity, patients require many medications to treat the symptoms, in addition to disease-modifying medications, to slow the progression of MS. Simultaneous use of multiple medications or PP can, in turn, lead to drug interactions.

The study authors assessed the medications of 627 patients with MS using 2 databases to determine the number of medications and pDDIs. The researchers defined total PP as 5 or more prescription or OTC medications and prescription PP (RxPP) as 5 or more prescription medications. More than half of the patients (53%) had PP and 63% of patients had at least 1 pDDIs.

Of the 627 patients, researchers detected 2887 pDDIs, most of which were mild (65%) or mildly moderate (17%). The study cited 7 (0.2%) severe DDIs that included the prescription medication citalopram used in combination with 1 of the following medications: ciprofloxacin, doxepin, flecainide, levofloxacin, ondansetron, and quetiapine. The most frequent interactions were between magnesium and cholecalciferol and acetylsalicylic acid and methylprednisolone.

In this study, researchers assessed the extent of PP and the prevalence and severity of pDDIs in patients with MS. Minimizing the potential of DDIs and reducing PP rates is crucial. Deprescribing unnecessary medications is the simplest approach to reduce PP rates and pDDIs.

Pharmacists should review the patient’s medications regularly to assess the potential for DDIs. When assessing medications, it’s important to include prescription drugs, OTC medications, and herbals/supplements. The researchers noted that 22% of pDDIs included OTC medications. Pharmacists must be proactive and always ask patients about OTC medication use.

Another approach includes the pharmacist performing a medication therapy management (MTM) service with the patient.2 MTM is effective in reducing health care costs, improving adherence, and enhancing clinical outcomes.

Last, pharmacists should always assess medication adherence. If patients are not taking their medications as prescribed, nonadherence could lead to treatment failure or adverse events. Prescribers could inadvertently start a cascade by prescribing more—and unnecessary—medications.

Safe medication use among patients is of utmost importance. Reducing polypharmacy can reduce the potential of DDIs, especially in those with severe chronic medical conditions.


  1. Bachmann P, Frahm N, Debus JL, et al. U.K. Prevalence and Severity of Potential Drug–Drug Interactions in Patients with Multiple Sclerosis with and without Polypharmacy. Pharmaceutics 2022, 14, 592. https:// doi.org/10.3390/
  2. American Pharmacists Association. National Association of Chain Drug Stores Foundation Medication therapy management in pharmacy practice: Core elements of an MTM service model (version 2.0). J. Am. Pharm. Assoc. 2008, 48, 341–353.
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