Is it safe to prescribe ascorbic acid for urinary acidification in stone-forming patients with alkaline urine?

Abstract

Objective: To study the effect of ascorbic acid (AA) supplementation on urinary pH, metabolic stone workup parameters, and development of de novo urolithiasis in stone-forming patients. Material and methods:A retrospective review of the patients followed-up at a tertiary stone centre between September 2009 and October 2015 was performed. Patients with recurrent urolithiasis who received AA supplementation as a urinary acidifying agent were included in the study. Detailed metabolic stone work-up, including two 24-hour urine collections obtained pre-and post-AA supplementation were compared. In addition, imaging studies were reviewed to assess the development of de novo urolithiasis.Results: Twenty-four patients were included in the study with a mean age of 60.6 years and a median daily AA dose of 1000 mg (range: 500-2000 mg). Median follow-up period was 22.6 months (range: 19.7-32.1). After AA supplementation, there was a significant decrease in urinary pH (7.6 vs. 6.9, p= 0.02). Although there was no significant increase in the daily oxalate excretion, two patients (8.3%) had their AA dose reduced or discontinued due to de novo hyperoxaluria (342.9 vs 510.2 umol/day; p= 0.75). Other serum and urinary parameters did not show any significant changes. Eight (33.3%) patients developed de novo urolithiasis with struvite and carbonate apatite being the major components. Conclusion:AA supplementation resulted in significantly lower urinary pH in patients with recurrent urolithiasis and alkaline urine pH. Prospective studies are needed to assess whether this reduction in urinary pH is associated with lower stone recurrence rates.

Womens' self‐management skills for prevention and treatment of recurring urinary tract infection

“…Vitamin C was used by almost one third of women. This proportion seems rather high, considering the limited evidence for the effectiveness of vitamin C and the risk of urolithiasis in doses of 500‐2000 mg/day 27 …”

Combined Application of Aminoglycosides and Ascorbic Acid in the Elimination of Proteus mirabilis Rods Responsible for Causing Catheter-Associated Urinary Tract Infections (CAUTIs)—A Molecular Approach

“…On the other hand, research by Borran et al [ 18 ] focused on the influence of AA on bacteriuria in kidney transplant patients and proved the effective action of a single dose of AA (70 mg kg −1 ) against the multiplication of bacteria. Moreover, Noureldin et al [ 44 ] showed a significant decrease in the urinary pH value (from 7.6 to 6.9) of 24 patients with recurrent urolithiasis after a 1000 mg daily dose of AA. Another urine-acidifying agent is L-methionine.…”

Phenytoin Toxicity with High Dose, Concomitant Ascorbic Acid Dosing

“…7 It is postulated a change in stomach acidity, increased urinary acidity, both or other contributing factors may have contributed to the increased phenytoin exposure, leading to the patient's toxic phenytoin levels. [7][8] Phenytoin has a dissociation constant (pKa) of 8, AA has a pKa of 4.2 and the pKa of hydrochloric acid (HCl) in the stomach is -8. The lower or more negative the number, the more acidic the substance.…”

“…Phenytoin and AA with higher Ka values would theoretically increase the overall Ka of the mixture. [6][7][8] However, other studies point to ascorbic acid overall increasing acid output, thus lowering pH. 9 Phenytoin metabolism is multifactorial, being affected by protein binding, oral formulation, pharmacogenomics (CYP2C9, CYP2C19) and possibly altered pH in the stomach and/or small intestine.…”