Furosemide high dose during breastfeeding: a case report

Background: Nephrotic syndrome (NS) is a glomerular disorder characterized by significant proteinuria, hypoalbuminemia, hyperlipidemia, and peripheral edema. Treatment involves high doses of corticosteroids, diuretics, and albumin. Although prednisone’s excretion into breast milk is considered negligible, furosemide has never been quantified in breast milk. However, it has a lower oral bioavailability (60–70%), high protein binding, it is used in full-term neonates and no adverse effects have been observed in breastfed infants whose mothers are treated with furosemide. Case Report: We report the case of a 28-year-old woman exclusively breastfeeding her 1-month-old infant. She presented with declivous edema and nephrotic proteinuria (20 g/day). Laboratory tests revealed renal impairment (S-Cr 1.3 mg/dL, eGFR 56 mL/min), severe hypoalbuminemia (18 g/L), hypercholesterolemia, and hypertriglyceridemia, with negative autoimmune tests. This clinical presentation was consistent with Minimal Change Disease (MCD). However, a renal biopsy was not performed due to the extended wait time for histological results. The patient was treated with intravenous (IV) prednisone (500 mg/day for 3 days), followed by oral prednisone (1 mg/kg/day), IV furosemide (20 mg four times a day), and 20% albumin (three times a day for 8 days), resulting in a rapid response and resolution of the nephrotic syndrome. Furosemide levels were measured in maternal plasma and breast milk. A blood sample was collected at 8 a.m., and milk samples were taken at 10 a.m., 4 p.m., and 12 p.m. Furosemide levels in the blood were 2.97 µg/mL, while milk concentrations were 1.27 µg/mL, 0.76 µg/mL and 0.49 µg/mL. The mother and infant remained together, and breastfeeding continued without any issues. The baby’s weight was monitored daily to ensure adequate weight gain. Discussion: The high concentration of furosemide in the milk is correlated with mother’s hypoalbuminemia. The RID (relative infant dose) decreases from 14% to 5.52%. after infusions of albumin. The baby had no side effects. Growth was regular. Conclusion: Hospitalisation of both mother and child allowed the best possible care to be given to the mother, while at the same time monitoring the health of the child. To determine the actual amount excreted in breastmilk, further analysis of furosemide in milk is required.