Alkalinizing Agents: A Review of Prescription, Over-the-Counter, and Medical Food Supplements

Pharmacologic treatment of kidney stones: Current medication and pH monitoring

Nephrolithiasis is a globally prevalent urologic condition associated with significant morbidity and patient discomfort. Current management of kidney stones includes both surgical and pharmacologic interventions. Though surgery may be necessary under certain circumstances, pharmacologic treatment is a more affordable, readily available, and a less invasive option for patients. A comprehensive scoping review was conducted to summarize the available literature on the pharmacologic strategies for managing the predominant stone types including calcium oxalate, calcium phosphate, uric acid, struvite, and cystine stones. Central to these therapeutic approaches is the regulation of factors such as urine pH, stone crystallization, and patient metabolics that precipitate stone development and growth. This review highlights the pharmacological options available for treating each kidney stone type, emphasizing the importance of patient tailored medical management that should be considered by every physician.

Effect of a high-citrate beverage on urine chemistry in patients with calcium kidney stones

A well-accepted strategy to prevent kidney stones is to increase urine volume by increasing oral intake of fluids, especially water, to lower supersaturation of the relevant, relatively insoluble salts, and thereby lower the risk of precipitation. Randomized controlled trials have shown that this strategy works. It is inexpensive, safe, and intuitively attractive to patients. However, although any beverage can increase urine volume, and citrus juices can increase urine citrate content and pH, no beverage other than water has been clearly shown by randomized controlled trial to prevent kidney stones. We designed an innovative, palatable, low-calorie, high alkali citrate beverage to prevent kidney stones, called Moonstone. One packet of Moonstone powder, mixed in 500 ml of water, contains 24.5 meq of alkali citrate. We administered one packet twice a day to ten calcium stone formers. Moonstone resulted in an increase in mean 24-h urine citrate and urine pH, and a decrease in supersaturation of calcium oxalate in calcium stone formers compared to an equal volume of water. These changes, comparable to those seen in a prior study of a similar amount of (potassium-magnesium) citrate, will likely be associated with a clinically meaningful reduction in kidney stone burden in patients with calcium stones. The effect to increase urine pH would also be expected to benefit patients with uric acid and cystine stones, groups that we hope to study in a subsequent study. The study preparation was well tolerated and was selected as a preferred preventative strategy by about half the participants. Moonstone is an alternative, over-the-counter therapy for kidney stone prevention.

Kidney Stone Prevention

Kidney stone disease (KSD) (alternatively nephrolithiasis or urolithiasis) is a global health care problem that affects almost people in developed and developing countries. Its prevalence has been continuously increasing with a high recurrence rate after stone removal. Although effective therapeutic modalities are available, preventive strategies for both new and recurrent stones are required to reduce physical and financial burdens of KSD. To prevent kidney stone formation, its etiology and risk factors should be first considered. Low urine output and dehydration are the common risks of all stone types, whereas hypercalciuria, hyperoxaluria, and hypocitraturia are the major risks of calcium stones. In this article, up-to-date knowledge on strategies (nutrition-based mainly) to prevent KSD is provided. Important roles of fluid intake (2.5-3.0 L/d), diuresis (>2.0-2.5 L/d), lifestyle and habit modifications (for example, maintain normal body mass index, fluid compensation for working in high-temperature environment, and avoid cigarette smoking), and dietary management [for example, sufficient calcium at 1000-1200 mg/d, limit sodium at 2 or 3-5 g/d of sodium chloride (NaCl), limit oxalate-rich foods, avoid vitamin C and vitamin D supplements, limit animal proteins to 0.8-1.0 g/kg body weight/d but increase plant proteins in patients with calcium and uric acid stone and those with hyperuricosuria, increase proportion of citrus fruits, and consider lime powder supplementation] are summarized. Moreover, uses of natural bioactive products (for example, caffeine, epigallocatechin gallate, and diosmin), medications (for example, thiazides, alkaline citrate, other alkalinizing agents, and allopurinol), bacterial eradication, and probiotics are also discussed. Adv Nutr 2023;x:xx-xx.

Alkali Citrate Content of Common Over-the-Counter and Medical Food Supplements

Objective: Potassium citrate effectively decreases kidney stone recurrence, but it is costly and associated with side effects. While several over-the-counter supplements and medical foods purport to provide sufficient citrate to prevent recurrent stones, corroborating data on their actual citrate content is limited. Materials and Methods: Nine common nonprescription products were purchased online. Reported citrate content was obtained from packaging, promotional materials, or ingredient labels. Using a single serving of each product, actual citrate, sodium, potassium, calcium, magnesium, and oxalate content was measured using spectrophotometry and chromatography. Total alkali citrate, cost, and amounts of each component per 10 mEq of alkali citrate were also calculated. Results: Nearly all products contained more citrate than advertised, except for Litholyte^® powder, Litholyte^® Coffee, and Horbäach^® potassium citrate. Per serving, Moonstone^® powder, LithoBalance™, and KSP tabs™ contained the most citrate (means of 63.9, 33.5, and 26.9 mEq, respectively). Moonstone and LithoBalance had the greatest discrepancy between total citrate and alkali citrate (15.7 and 11.8 mEq per serving, respectively). NOW^® potassium citrate was least expensive ($0.04/10 mEq alkali citrate). KSP tabs delivered the most daily sodium (mean 158 mg/10 mEq alkali citrate, Litholyte Coffee provided the most potassium (mean of 13 mEq/10 mEq alkali citrate), and Kidney COP^® provided the most calcium (mean 147 mg/10 mEq alkali citrate). Conclusion: Some common over-the-counter products contain sufficient alkali to potentially promote a citraturic response; Moonstone provides the most alkali citrate, but at a higher cost than other products. Sodium, potassium, and calcium from these products must also be considered in daily consumption.

Over-the-counter alkali agents to raise urine pH and citrate excretion: a prospective crossover study in healthy adults

OBJECTIVE

To assess the effect of two over-the-counter alkalizing agents on 24-hour urinary parameters.

MATERIALS AND METHODS

Ten healthy volunteers without a history of kidney stones were recruited to complete a baseline 24-hour urinalysis with a four-day diet inventory. Participants then maintained the same diet on either LithoLyte® (20 mEq two times per day) or KSPtabs^TM (1 tablet two times per day) and submitted another 24-hour urinalysis. The process was repeated with the other supplement. Urinary alkali parameters were compared to baseline, and side effects were elicited with a questionnaire.

RESULTS

LithoLyte® intake resulted in a non-significant increase in citrate (597 to 758 mg/day, p=0.058, an increase in urine pH (6.46 to 6.66, p=0.028), and a decrease in urine ammonium (41 to 36 mmol/day, p=0.005) compared to baseline. KSPtabs^TM resulted in an increase in citrate (597 to 797 mg/day, p=0.037) and urine pH (6.46 to 6.86, p=0.037), with a non-significant decrease in ammonium (41 to 34 mmol/day, p=0.059). No significant differences were seen comparing urinary analytes between LithoLyte® and KSPtabs^TM. With Litholyte®, no side effects, mild, moderate, and severe side effects were seen in 50%, 40%, 10%, and 0%, respectively. With KSPtabs^TM, rates were 60%, 20%, 10%, and 10%, respectively.

CONCLUSIONS

In healthy participants without a history of kidney stones, LithoLyte® and KSPtabs^TM are effective over-the-counter alkali supplements, with a similar side effect profile to prescription potassium citrate.

Effect of alkalized urine on renal calculi in patients with gout: a protocol for a placebo-controlled, double-blinded randomized controlled trial

Background

The prevalence of renal calculi in patients with gout is high. Alkalized urine has been recommended by the 2020 European Association of Urology (EAU) guidelines to promote calculus dissolution. However, randomized controlled trials are lacking.

Methods

In the protocol of this randomized, placebo-controlled, double-blinded trial, patients with gout combined with renal calculi are randomized (1:1) to the placebo and sodium bicarbonate groups. The intervention would be performed for 24 weeks, the 1–12 weeks are double-blinded, and the 13–24 weeks are open-labeled. Sodium bicarbonate (1 g tid) will be performed for 24 weeks in the sodium bicarbonate group. The placebo will be performed for 12 weeks and not be performed from 13 weeks to 24 weeks in the placebo group. All subjects will be administered febuxostat (40 mg/day) for 24 weeks and receive concomitant anti-inflammatory prophylaxis therapy for 12 weeks. The primary outcome is the proportion of patients whose renal calculus volume will be reduced after 12 weeks of treatment. The secondary outcomes include the volume changes of renal calculi, uric acid changes, the proportion of patients with serum uric acid (sUA) levels < 360 μmol/L, the changes in estimated glomerular filtration rate (eGFR), the pH value of urine, and the incidence of adverse events after treatment for 12 and 24 weeks.

Discussion

This study will evaluate the efficacy and safety of sodium bicarbonate-alkalized urine on renal calculi in patients with gout.

Trial registration

ClinicalTrials.gov ChiCTR2100045183. Registered on April 7, 2021, with ChiCTR.

Sodium Bicarbonate Prescription and Extracellular Volume Increase: Real-world Data Results from the AlcalUN Study

Oral alkalization with sodium bicarbonate (NaHCO₃ ) or citrate is prescribed for conditions ranging from metabolic acidosis to nephrolithiasis. Although most nephrologists/urologists use this method routinely, extracellular volume (ECV) increase is the main feared adverse event reported for NaHCO₃ . Thus far, no trial has specifically studied this issue in a real-world setting. AlcalUN (NCT03035812) is a multicentric, prospective, open-label cohort study with nationwide (France) enrollment in 18 (public and private) nephrology/urology units. Participants were adult outpatients requiring chronic (>1 month) oral alkalization by either NaHCO₃ -containing or no-NaHCO₃ -containing agents. The ECV increase (primary outcome) was judged based on body weight increase (ΔBW), blood pressure increase (ΔBP), and/or new-onset edema at the first follow-up visit (V1). From February 2017 to February 2020, 156 patients were enrolled. After a median 106 days of treatment, 91 (72%) patients reached the primary outcome. They had lower systolic (135 (125, 141) vs. 141 (130, 150), P = 0.02) and diastolic (77 (67, 85) vs. 85 (73, 90), P = 0.03) BP values, a higher plasma chloride (106.0 (105.0, 109.0) vs. 105.0 (102.0, 107.0), P = 0.02) at baseline, and a less frequent history of nephrolithiasis (32 vs. 56%, P = 0.02). Patients experienced mainly slight ΔBP (< 10 mmHg). The primary outcome was not associated (P = 0.79) with the study treatment (129 received NaHCO₃ and 27 received citrate). We subsequently developed three different models of propensity score matching; each confirmed our results. Chronic oral alkalization with NaHCO₃ is no longer associated with an ECV increase compared to citrate in real-life settings.

Complementary and Alternative Medicine Use in First-time and Recurrent Kidney Stone Formers

OBJECTIVE

To describe the patterns of complementary and alternative medicine (CAM) among patients with kidney stones and analyze the alkali content of commonly used CAM therapies.

METHODS

We prospectively conducted structured interviews with patients who presented to a specialty stone clinic for the management of kidney stones. Open-ended questions were used to elicit information regarding CAM knowledge, formulation/dosing, and patterns of use. Several common CAM therapies were then analyzed for their alkali, organic anion, and sugar content.

RESULTS

Of 103 subjects, 82 (80%) patients reported knowledge of CAM and 52 (50%) reported using CAM. Patients with recurrent kidney stones were more likely to report using CAM than patients with first-time episodes (56% vs 26%, P = 0.04). Some respondents reported their condition decreased in severity or frequency since starting CAM therapy (17%) and improvements in pain (12%). Total alkali content per serving of the tested supplements was 0 mEq (Stonebreaker), 1.5 mEq (Ocean Spray Cranberry Juice Cocktail), 4.7 mEq (Lakewood Pure Cranberry Juice), 0.6 mEq (Braggs Apple Cider Vinegar), 11.9 mEq (LithoBalance), 9.5 mEq (Simply Grapefruit Juice), 19.8 mEq (KSP-Key Lime), and 20.2 mEq (KSP-Very Berry).

CONCLUSION

Patients with kidney stones may use CAM to alleviate symptoms or prevent recurrence. Commercially available CAM therapies may contain comparable alkali content to commonly prescribed citrate therapy. These data suggest that providers should be prepared to discuss the role of CAM with their patients.

Causes and prevention of kidney stones: separating myth from fact

Despite high-level evidence supporting the use of pharmacotherapy therapy for the prevention of kidney stones, adherence to medications is often poor because of side-effects, inconvenience and cost. Furthermore, with a desire for more 'natural' products, patients seek dietary and herbal remedies over pharmacotherapy. However, patients are often unaware of the potential side-effects, lack of evidence and cost of these remedies. Therefore, in the present review we examine the evidence for a few of the commonly espoused non-prescription agents or dietary recommendations that are thought to prevent stone formation, including lemonade, fish oil (omega fatty acids), Phyllanthus niruri and the Dietary Approaches to Stop Hypertension (DASH) diet. While the present review includes only a few of the stone-modulating recommendations available to the lay community, we focussed on these four due to their prevalent use. Our goal is not to only dispel commonly held notions about stone disease, but also to highlight the lack of high-level evidence for many commonly utilised treatments.

The efficacy and safety of citrate mixture vs sodium bicarbonate on urine alkalization in Chinese primary gout patients with benzbromarone: a prospective, randomized controlled study

Objectives

To compare the efficacy and safety of citrate mixture and sodium bicarbonate on urine alkalization in gout patients under benzbromarone treatment.

Methods

A prospective, randomized, parallel controlled trial was conducted among 200 gout patients in the dedicated gout clinic of the Affiliated Hospital of Qingdao University. The participants were randomly divided into two groups (1:1), sodium bicarbonate group (3 g/day) and citrate mixture group (7 g/day). All patients were prescribed with 25 mg/day benzbromarone at initiation and maintained at a dose of 50 mg/day. Clinical and biochemical data were collected at each follow-up time point (baseline, weeks 2, 4, 8 and 12).

Results

A total of 182 patients completed the 12-week urine alkalization study. The urine pH value of both groups increased significantly from the baseline to the final follow-up time point (sodium bicarbonate group, 5.50–6.00, P < 0.05; citrate mixture group, 5.53–5.93, P < 0.05). While the comparisons regarding urine pH between treatment groups showed no significant differences for each time point. The estimated glomerular filtration rate (eGFR) dropped significantly after 12 weeks’ trial in the sodium bicarbonate group (P < 0.01), while it was comparable between baseline and the last follow-up (P > 0.05) in the citrate mixture group. Results of urine analysis showed that the incident rate of occult blood in the sodium bicarbonate group was higher than that in the citrate mixture group (38 vs 24%, P < 0.05), accompanied by a similar occurrence of kidney stones. After 12-week follow-up, the frequency of twice gout flare in the citrate mixture group was significantly lower than that in sodium bicarbonate group (4 vs 12%, P = 0.037). No treatment-emergent adverse events occurred.

Conclusion

The efficacy of citrate mixture on urine alkalization is comparable to sodium bicarbonate under benzbromarone treatment without significant adverse events. Citrate mixture is superior to sodium bicarbonate in lowering the incidence of urine occult blood and the frequency of gout attacks.

Trial registration

Registered with ChiCTR (http://www.chictr.org.cn), No. ChiCTR1800018518.

Roles of interstitial fluid pH and weak organic acids in development and amelioration of insulin resistance

Type 2 diabetes mellitus (T2DM) is one of the most common lifestyle-related diseases (metabolic disorders) due to hyperphagia and/or hypokinesia. Hyperglycemia is the most well-known symptom occurring in T2DM patients. Insulin resistance is also one of the most important symptoms, however, it is still unclear how insulin resistance develops in T2DM. Detailed understanding of the pathogenesis primarily causing insulin resistance is essential for developing new therapies for T2DM. Insulin receptors are located at the plasma membrane of the insulin-targeted cells such as myocytes, adipocytes, etc., and insulin binds to the extracellular site of its receptor facing the interstitial fluid. Thus, changes in interstitial fluid microenvironments, specially pH, affect the insulin-binding affinity to its receptor. The most well-known clinical condition regarding pH is systemic acidosis (arterial blood pH < 7.35) frequently observed in severe T2DM associated with insulin resistance. Because the insulin-binding site of its receptor faces the interstitial fluid, we should recognize the interstitial fluid pH value, one of the most important factors influencing the insulin-binding affinity. It is notable that the interstitial fluid pH is unstable compared with the arterial blood pH even under conditions that the arterial blood pH stays within the normal range, 7.35-7.45. This review article introduces molecular mechanisms on unstable interstitial fluid pH value influencing the insulin action via changes in insulin-binding affinity and ameliorating actions of weak organic acids on insulin resistance via their characteristics as bases after absorption into the body even with sour taste at the tongue.

Using Low-Calorie Orange Juice as a Dietary Alternative to Alkali Therapy

Purpose: The pursuit of a dietary source to increase urine pH and citrate in stone formers has been ongoing for >30 years. Early evidence showed that orange juice (OJ) contains alkali and citrate, but high sugar and ascorbic acid content limited the use of OJ as a viable daily source of alkali. Recently, novel low-calorie OJs have emerged and could potentially be a better option. Methods: Beverages with high concentrations of alkali citrate and malate were identified using ion chromatography. Two low-calorie OJ beverages, in addition to crystal light lemonade beverage (CLLB), were chosen. Healthy volunteers (5 men, 5 women) drank 1 L of OJ or CLLB with 1 L water daily for 7 days, and then completed a 24-hour urinalysis. A washout week was instituted between trial weeks. The study design is a prospective randomized crossover control trial. A paired analysis using comparison of means was used to evaluate low-calorie OJ and CLLB. Volunteers had no prior history of kidney stones and maintained a journal with beverage compliance, side effect (SE), and dietary consumption data. Results: Tropicana 50 (TRP50), Kroger low-calorie OJ (KLCO), and CLLB were found to have a total alkali content of 56.60, 47.9, and 17.3 mEq/L, respectively, based on ion chromatography. Consumption of all three beverages raised urinary citrate (116.6 [-118 to 373, 177.9 [-3 to 359], 155.6 [-4 to 237] ▵mg/day 95% confidence interval) and urinary pH (0.25 [0.08-0.53], 0.74 [0.41-1.07 p < 0.05], 0.25 [0.25-0.64]), respectively, compared with water phase. Based on journal entries by volunteers, TRP50 had the most SEs (90% participants) felt to be a result of the artificial sweetener (Stevia^®). Conclusion: Low-calorie OJs, and to a lesser extent CLLB, have alkali and citrate based on ion chromatography. Daily consumption by healthy volunteers of KLCO can raise urinary pH.