Oral Furosemide and Hydrochlorothiazide/Amiloride versus Intravenous Furosemide for the Treatment of Resistant Nephrotic Syndrome

Background: Data on diuretic treatment in nephrotic syndrome (NS) are scarce. Our goal was to assess the non-inferiority of the combined oral diuretics (furosemide/hydrochlorothiazide/amiloride) compared to intravenous (i.v.) furosemide in patients with NS and resistant edema. Methods: We conducted a prospective randomized trial on 22 patients with resistant nephrotic edema (RNE), defined as hypervolemia and a FENa < 0.2%. Based on a computer-generated 1:1 randomization, we assigned patients to receive either intravenous furosemide (40 mg bolus and then continuous administration of 5 mg/h) or oral furosemide (40 mg/day) and hydrochlorothiazide/amiloride (50/5 mg/day) for a period of 5 days. Clinical and laboratory measurements were performed daily. Hydration status was assessed by bioimpedance on day 1 and at the end of day 5 after treatment initiation. The primary endpoint was weight change from baseline to day 5. Secondary endpoints were hydration status change measured by bioimpedance and safety outcomes (low blood pressure, severe electrolyte disturbances, acute kidney injury and worsening hypervolemia). Results: Primary endpoint analysis showed that after 5 days of treatment, there was a significant difference in weight change from baseline between groups [adjusted mean difference: −3.33 kg (95% CI: −6.34 to −0.31), p = 0.03], with a higher mean weight change in the oral diuretic treatment group [−7.10 kg (95% CI: −18.30 to −4.30) vs. −4.55 kg (95%CI: −6.73 to −2.36)]. Secondary endpoint analysis showed that there was no significant difference between groups regarding hydration status change [adjusted mean difference: −0.05 L (95% CI: −2.6 to 2.6), p = 0.96], with a mean hydration status change in the oral diuretic treatment group of −4.71 L (95% CI: −6.87 to −2.54) and −3.91 L (95% CI: −5.69 to −2.13) in the i.v. diuretic treatment group. We observed a significant decrease in adjusted mean serum sodium of −2.15 mmol/L [(95% CI: −4.25 to −0.05), p = 0.04]), favored by the combined oral diuretic treatment [−2.70 mmol/L (95% CI: −4.89 to −0.50) vs. −0.10 mmol/L (95%CI: −1.30 to 1.10)]. No statistically significant difference was observed between the two groups in terms of adverse events. Conclusions: A combination of oral diuretics based on furosemide, amiloride and hydrochlorothiazide is non-inferior to i.v. furosemide in weight control of patients with RNE and a similar safety profile.