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Abstract: PO1475

Amiloride Effects on Urine Calcium in the Setting of Urolithiasis

Session Information

Category: Fluid, Electrolyte, and Acid-Base Disorders

  • 902 Fluid, Electrolyte, and Acid-Base Disorders: Clinical

Authors

  • Ahmadieh, Kian, Mayo Clinic Arizona, Scottsdale, Arizona, United States
  • Moore, Jonathan, Mayo Clinic Arizona, Scottsdale, Arizona, United States
  • Patel, Maya, The University of Arizona College of Medicine Phoenix, Phoenix, Arizona, United States
  • Keddis, Mira T., Mayo Clinic Arizona, Scottsdale, Arizona, United States
  • Stern, Karen L., Mayo Clinic Arizona, Scottsdale, Arizona, United States
Background

Medical management of urolithiasis often targets the biochemical properties of urine to prevent further development of stone burden. Thiazide diuretics are commonly used for recurrent stone formation in patients with hypercalciuria. However, data related to the use of potassium-sparing diuretic amiloride is relatively scarce and the aim of this study is to investigate amiloride’s effects on urinary calcium and other properties of urine in prevention of urolithiasis.

Methods

All nephrolithiasis patients who were prescribed amiloride for treatment of hypercalciuria between the years 2011 and 2019 at a single tertiary care center were retrospectively reviewed. Patients met criteria if they had a pre and post treatment 24 hour urine collections. Pre and post urinary calcium levels were compared. Other comparative measures include levels of other stone risk factors measured on urine collections, stone events on treatment and adverse reaction to medication.

Results

A total of 31 patients were started on amiloride. Of those, 15 patients tolerated the medication and completed follow-up urine testing. Amiloride was given due to intolerance of thiazide (11, 73%), persistent hypercalciuria on thiazide (3, 20%), or as combination with thiazide (1, 7%). Maximum treatment dose ranged from 2.5 mg daily to 5 mg BID. Mean duration on treatment was 57.2 months (SD 32.5;9-96). Three (20%) patients stopped due to delayed intolerance and 2 (13%) due to elevated urinary calcium. In the overall cohort, there was no significant difference in urine parameters (Table 1) including urinary calcium (286.3 mg/day pre vs 310.0 mg/day post, p=0.552). Three (20%) had a stone event at a mean of 23.3 months on treatment with 1 surgery, and 2 passage of stones. Six (40%) patients showed metabolic activity with new or growing stones.

Conclusion

In patients that have failed thiazides for treatment of hypercalciuria, switching to or adding amiloride did not result in lower urinary calcium levels.

24 Hour Urine Parameters before and after amiloride treatment
24 urine ParameterPre-amiloride (SD)Post-amiloride (SD)P-value
Volume (L)2.37 (0.93)2.69 (0.86)0.316
SS Calcium Oxalate7.15 (3.74)6.22 (2.8)0.078
Calcium mg/day286.3 (103.8)310.0 (175.6)0.552
Oxalate (mg/d)42.5 (16.6)37.5 (7.94)0.316
SS Calcium Phosphate1.52 (1.16)1.09 (0.80)0.193
Na (mmol/d)149.7 (60)168.5 (89)0.316