RIMSO-50 Drug Interactions: What to Avoid and What to Tell Your Doctor

Before receiving RIMSO-50 (dimethyl sulfoxide) bladder instillation therapy for interstitial cystitis, you will likely hear your provider say: "Make sure you tell us about all the medications you are taking." This is standard medical advice — but with RIMSO-50, there are specific reasons it matters.

This guide covers what is known about RIMSO-50 drug interactions, what the FDA's prescribing information says, and what you should disclose to your healthcare team.

What Do the Official Drug Interaction Guidelines Say?

According to the FDA-approved prescribing information for RIMSO-50, no specific drug interactions are currently listed. The prescribing information states: "None known." However, the labeling includes an important warning that many patients and providers overlook:

"Some data indicate that dimethyl sulfoxide could change the effectiveness of medication(s) that you may be presently receiving." This means that DMSO's extraordinary membrane-penetrating ability may alter how other drugs are absorbed, distributed, or metabolized in the body.

Why DMSO Can Affect Other Medications

DMSO is one of the most membrane-permeable substances known. When it is absorbed into the bloodstream after instillation, it can:

Enhance absorption of other drugs: DMSO can increase the permeability of cell membranes throughout the body, potentially causing other drugs to be absorbed more rapidly or at higher concentrations than intended.

Alter drug metabolism: DMSO may affect liver enzyme activity, potentially changing how quickly certain drugs are broken down. This could increase or decrease the effective concentration of medications in the bloodstream.

Act as a carrier vehicle: In topical or experimental applications, DMSO is known to carry other substances across the skin barrier. The same principle may apply systemically after intravesical absorption, potentially carrying co-administered substances into tissues where they would not otherwise reach.

What Medications Are Most Important to Disclose?

While no specific interactions have been formally documented, the categories of medications most worth discussing with your provider before starting RIMSO-50 include:

Anticoagulants (blood thinners): Warfarin (Coumadin), apixaban (Eliquis), rivaroxaban (Xarelto), dabigatran (Pradaxa). DMSO may affect the absorption or activity of blood thinners. Patients on anticoagulation should be monitored closely.

Immunosuppressants: Medications like cyclosporine, tacrolimus, or mycophenolate used in transplant patients or autoimmune conditions. DMSO's effect on drug absorption could affect narrow therapeutic index drugs like these significantly.

Cardiovascular medications: Digoxin and other cardiac glycosides have narrow therapeutic windows and could theoretically be affected.

Sedatives, opioids, and CNS depressants: If DMSO enhances the absorption of CNS-active medications, the effect could be amplified. Let your provider know about any sedating medications, sleeping aids, or opioid pain medications.

Chemotherapy drugs: DMSO has been studied experimentally as a drug penetration enhancer for chemotherapy. If you are receiving or have recently received chemotherapy, discuss RIMSO-50 use carefully with your oncologist.

Supplements and OTC Products to Disclose

Many patients do not think to mention over-the-counter medications or supplements, but some are relevant:

NSAIDs (ibuprofen, naproxen): Commonly used for IC pain management. No known interaction, but disclose to your provider.

Herbal supplements with blood-thinning properties: Garlic supplements (ironically), ginkgo biloba, fish oil in large doses, vitamin E.

CBD and cannabis products: These interact with the same liver enzymes (CYP450 system) that process many drugs. DMSO's potential effects on enzyme activity make these particularly worth mentioning.

Food and Alcohol Interactions

There are no known interactions between RIMSO-50 and specific foods. Regarding alcohol, the effect of concurrent alcohol use on RIMSO-50 therapy is not formally studied. As a general precaution, avoiding heavy alcohol use around the time of treatment is reasonable.

The Bottom Line: Disclose Everything

Because DMSO has the potential to modify how other drugs behave in the body — even if specific interactions are not formally documented — the safest approach is to give your provider a complete list of everything you take: prescription drugs, OTC medications, vitamins, supplements, and herbal products. Your provider may want to time RIMSO-50 instillations away from doses of narrow-therapeutic-index drugs, or monitor levels more closely during treatment.

For more on RIMSO-50 side effects, see: RIMSO-50 Side Effects: What to Expect and When to Call Your Doctor.

Need help finding RIMSO-50 in stock near you? medfinder contacts pharmacies on your behalf to check availability and texts you the results.