Cyclophosphamide Use in Multiple Sclerosis: Levels Detected in Human Milk

Multiple sclerosis (MS) is a chronic autoimmune inflammatory neurological disease of the central nervous system. It is the most common immune-mediated disorder, affecting >2 million people worldwide. Cyclophosphamide is an alkylating agent commonly used to treat both malignancies and immune-mediated inflammatory nonmalignant processes. At present, there are no data available on its use in breastfeeding mothers.

In this study we report a 33-year-old mother who was suffering from MS. To treat her MS, stem cell transplantation protocol required preparation with multiple doses of cyclophosphamide. She had been exclusively breastfeeding for 6 months before undertaking this regimen. She voluntarily collected her milk samples at critical time points after the intravenous doses of 2.8 g cyclophosphamide for each of 4 days. Quantification of cyclophosphamide was determined using liquid chromatography coupled with tandem mass spectrometry.

Low levels in milk were determined for cyclophosphamide as the area under the curve was 364.1 μg.hour/mL on day 1 and 113.9 μg.hour/mL on day 4. Maximum concentration of cyclophosphamide was observed on day 1 at 40.82 μg/mL, which peaked at 4 hours. For 24 hours, the levels gradually receded to minimum concentrations. The average relative infant dose (RID) for a period of 4 days varied from 4.7% at day 1 to 0.9% at day 4.

Cyclophosphamide is transferred into breast milk in measurable quantities. This case report found RID of cyclophosphamide to be relatively low. However, great caution should be taken in counseling mothers regarding breastfeeding with this toxic drug.