Intervention with dimethyl sulfoxide (DMSO) remains a cornerstone in managing refractory interstitial cystitis (IC). While its clinical efficacy is well-documented, data regarding DMSO breastfeeding safety has historically been scarce. Consequently, clinicians often faced a dilemma when treating lactating patients due to the lack of pharmacokinetic data. A breakthrough study by Yamada E et al. now provides the first quantification of DMSO concentrations in human milk, offering much-needed clarity for maternal and neonatal care.

The study utilized liquid chromatography-mass spectrometry to analyze milk samples after a standard Rimso-50 intravesical treatment. Researchers observed a maximum concentration (Cmax) of 34.5 μg/mL approximately five hours post-treatment. Crucially, the researchers calculated the Relative Infant Dose (RID) at just 0.45%. Since clinical guidelines typically consider an RID of less than 10% as safe, these findings suggest that the systemic transfer of DMSO to the infant is minimal. Therefore, the estimated infant dose of 2 mg/kg/day represents a low risk for most healthy infants.

Clinical Implications for DMSO Breastfeeding Safety

For urologists and gynecologists, this evidence facilitates more informed counseling for patients with bladder pain syndrome. Although mucous membranes rapidly absorb DMSO, the low RID suggests that maternal symptom relief likely outweighs the theoretical risks to the breastfed infant. Providers should still maintain open communication with patients regarding the timing of treatment and breastfeeding sessions to further minimize exposure.

Nevertheless, clinicians should continue to monitor for the characteristic "garlic-like" odor in both the mother and potentially the infant. This odor is a known byproduct of DMSO metabolism and excretion. Additionally, the study marks the first time that DMSO has been quantified in human milk, filling a significant gap in urological and obstetric pharmacology. While this initial quantification is a significant step forward, further observation of long-term neonatal outcomes remains beneficial for comprehensive safety profiles.

Is DMSO safe to use while breastfeeding?

Recent research indicates that DMSO transfer into human milk is minimal. With a Relative Infant Dose (RID) of 0.45%, it falls well below the standard 10% safety threshold used by medical experts to determine drug compatibility with lactation.

What is the peak time for DMSO in breast milk?

The study found that the maximum concentration of DMSO in human milk occurs approximately five hours after the intravesical instillation of the medication.

Should I stop breastfeeding during Rimso-50 treatment?

Based on the minimal transfer observed in this study, cessation of breastfeeding may not be necessary. However, you should discuss the timing of your treatments and feeding schedule with your urologist to ensure the highest level of safety.

Disclaimer: This content is for informational and educational purposes only. It does not constitute medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Refer to the latest local and national guidelines for clinical practice.

References

Yamada E et al. Bladder to Breast Milk-DMSO Treatment of Interstitial Cystitis. Breastfeed Med. 2026 May 23. doi: 10.1177/15568253261454248. PMID: 42175747.

Rawls WF, Cox L, Rovner ES. Dimethyl sulfoxide (DMSO) as intravesical therapy for interstitial cystitis/bladder pain syndrome: A review. Neurourol Urodyn. 2017.

American Urological Association (AUA). Diagnosis and Treatment of Interstitial Cystitis/Bladder Pain Syndrome. Clinical Guidelines, 2022.