ASN's Mission

ASN leads the fight to prevent, treat, and cure kidney diseases throughout the world by educating health professionals and scientists, advancing research and innovation, communicating new knowledge, and advocating for the highest quality care for patients.

learn more

Contact ASN

1401 H St, NW, Ste 900, Washington, DC 20005


The Latest on Twitter

Kidney Week

Abstract: PO1486

Anion Gap (AG) and Negative Osmotic Gap (OG) due to Remdesivir’s (R) Excipient

Session Information

Category: Fluid, Electrolyte, and Acid-Base Disorders

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


  • Alqassimi, Sameer, USF Health Morsani College of Medicine, Tampa, United States
  • Chavez, Octavio, USF Health Morsani College of Medicine, Tampa, Florida, United States
  • Bassil, Claude, USF Health Morsani College of Medicine, Tampa, Florida, United States
  • Jain, Pranjal, Florida Kidney Physicians, Tampa, Florida, United States
  • Durr, Jacques A., USF Health Morsani College of Medicine, Tampa, Florida, United States

Group or Team Name

  • USF Nephrology and Hypertension

The FDA authorized R for COVID-19. Excess Na sulfobutylether (SBE) substituted β-cyclodextrin (CD) solubilizes R (PMID: 32376442). Minute accumulation of SBECD can cause an AG as n, its substitution in SBE is 6.5 (Captisol). The FDA advises against using R in adults with eGFR ≤30 mL/min unless the potential benefit outweighs the potential risks because SBECB accumulates. We report 2 cases of AG with the FDA protocol.

Case Description

Case A: 77 obese ♀ with bilateral AKA, and initial serum creatinine (Scr) of 1 mg/dL, currently decreasing (0.6 mg/dL). On day 5 R was initiated while a mild ketosis resolved (β OH-butyrate 0.6→0.3→0.1 mmol/L). An AG as high as 16 mmol/L (Alb ~2 g/dL) ensued, wherein the AG of the 1st blood sample after each R infusion correlated inversely with the time elapsed after the infusion. Like ketones, lactate was low throughout R therapy. By the time R started, Scr had risen and plateaued at 1.8 mg/dL and the AG mirrored the subsequent increase and decrease in Scr, and vanished by day 9, when her Scr was < 1.7, after peaking at 2.6 mg/dL, in spite of continuing R, consistent with SBECD cleared by GFR, like cr. Her initial normal Scr already meant AKI in this elderly sedentary, bilateral AKA patient. Her OG, only 7 on day 2 of R, further decreased by 11, to a negative OG of –4 mOsm/Kg H2O the next day, suggesting polyanion accumulation. The calculated osmolarity of a NanSBECD solution is ((n + 1)/n)*[Na] = 1.15*[Na], not 2*[Na] since n ≈ 6.5, which explains the negative OG. Case B: 42 ♀, with morbid obesity and initial Scr of 1 mg/dL. R started on day 2, as Scr rose fast but her AG was 10 mmol/L. Again, the AG rapidly rose to 16 mmol/L (Alb. ~2.5 g/dL), and paralleled the rise and drop in Scr. CRRT was started when Scr was 6 mg/dL. Here again, prior to CRRT the AGs of the 1st samples following each R infusion were inversely related with the time from R infusion. While R was continued, CRRT caused parallel decreases in AG and Scr, since it clears cr and SBECD equally. The R loading dose contains 6 g and the 9 subsequent daily doses 3 g SBECD. Since the mass of SBE6.5CD is 2163.3 D, the initial anion load is ~18 mmol, followed by 9 daily loads of ~ 9-10 mmol.


Depending on plasma volume, rate of escape from plasma, GFR, and timing after the infusion, SBECD can cause an AG, and negative OG, when the GFR is low.