Clinical efficacy of urea treatment in syndrome of inappropriate antidiuretic hormone secretion

Syndrome of Inappropriate Antidiuresis

Syndrome of inappropriate antidiuresis (SIAD)-the most frequent cause of hypotonic hyponatremia-is mediated by nonosmotic release of arginine vasopressin, which promotes water retention by activating renal vasopressin type 2 (V2) receptors. There are numerous causes of SIAD, including malignancy, pulmonary and central nervous system diseases, and medications. Rare activating mutations of the V2 receptor can also cause SIAD. Determination of the etiology of SIAD is important because removal of the stimulus for inappropriate arginine vasopressin secretion offers the most effective therapy. Treatment of SIAD is guided by symptoms and their severity, as well as the level of plasma sodium. In the absence of severe symptoms, which require urgent intervention, many clinicians focus on fluid restriction as a first-line treatment. Second-line therapeutic options include loop diuretics and salt tablets, urea, and V2 receptor antagonists.

Urea to Treat Hyponatremia Due to Syndrome of Inappropriate Antidiuretic Hormone Secretion: A Systematic Review and Meta-Analysis

RATIONALE & OBJECTIVE

The use of urea to treat hyponatremia related to the syndrome of inappropriate antidiuretic hormone secretion (SIADH) has not been universally adopted due to questions about effectiveness, safety, and tolerability. This systematic review and meta-analysis of observational studies addresses these questions.

STUDY DESIGN

This PRISMA-guided study examined published research across 4 electronic databases.

STUDY POPULATIONS

Patients with SIADH-related hyponatremia.

SELECTION CRITERIA

Clinical trials and observational studies reporting at least 1 outcome related to serum sodium concentration, symptom resolution, or adverse effects after oral or nasogastric urea administration.

DATA EXTRACTION

Data extraction was performed independently by 2 reviewers using a standardized form recording study characteristics, participant demographics, intervention details, and treatment outcomes.

ANALYTICAL APPROACH

A meta-analysis was conducted using the restricted maximum likelihood method for the random effects model to assess the effect of urea treatment on serum sodium and serum urea compared with other treatment modalities. Subgroup analyses were conducted based on treatment duration and SIADH severity.

RESULTS

Urea treatment significantly increased serum sodium (mean difference [MD], 9.08 [95% CI, 7.64-10.52], P<0.01) and urea (MD, 31.66 [95% CI, 16.05-47.26], P<0.01) in patients with SIADH, albeit with significantly high heterogeneity. Subgroup analysis based on the treatment duration showed a significant rise in the serum sodium level after 24 hours and 2, 5, 7, and 14 days, as well as after 1 year of treatment. Greater increases in serum sodium levels after treatment with urea occurred in patients with severe (<120 mEq/L) (MD, 18.04 [95% CI, 13.68-22.39]) than with moderate (120-129 mEq/L) (MD, 7.86 [95% CI, 6.78-8.94]) or mild (130-135 mEq/L) (MD, 8.00 [95% CI, 7.31-8.69]) SIADH-induced hyponatremia. Urea treatment was comparable to fluid restriction (MD, 0.81 [95% CI, -0.93 to 2.55], P = 0.4) and vaptans (MD, -1.96 [95% CI, -4.59 to 0.66], P=0.1) but superior to no treatment (MD, 7.99 [95% CI, 6.25-9.72], P<0.01). Urea was associated with minor adverse events, with poor palatability being the most common.

LIMITATIONS

As no randomized controlled trials investigating urea as a treatment for hyponatremia were identified for inclusion, these analyses were based on observational studies.

CONCLUSIONS

Urea is safe and effective for managing SIADH-induced hyponatremia. These finding suggest that urea may be a useful treatment modality in resource-limited settings or when other treatments are contraindicated or poorly tolerated.

TRIAL REGISTRATION

Registered at PROSPERO with study number CRD42024511685.

Syndrome of inappropriate antidiuretic hormone secretion as an adverse reaction of ciprofloxacin: a case report and literature review

Antidiuretic hormone (ADH) is secreted by the posterior pituitary gland. Unsuppressed release of ADH leads to hyponatremia. This condition is referred to as syndrome of inappropriate antidiuretic hormone secretion (SIADH). Hereby, a case report is presented on ciprofloxacin-induced SIADH. A 67-year-old male patient was examined in the emergency room with symptoms of lethargy, headache, lack of attention, and a generally depressed mood lasting for three days. One week prior, empirical antimicrobial therapy involving ciprofloxacin for prostatitis was initiated. Laboratory analysis showed no relevant abnormalities except for hyponatremia (Na = 129 mmol/L). Chronic hyponatremia, thyroid dysfunction, and adrenal dysfunction were ruled out. Serum osmolality was 263 mOsmol/kg, urine osmolality was 206 mOsmol/kg, and urine sodium was 39 mmol/L. Given that all criteria for SIADH were met, ciprofloxacin was discontinued, and fluid restriction was advised. Four days later, the patient's serum sodium concentrations nearly normalized (Na = 135 mmol/L), and all symptoms resolved. The Naranjo Scale yielded a score of 8, supporting the likelihood of a probable adverse reaction to ciprofloxacin. This case is presented to raise awareness among clinicians about the potential of ciprofloxacin to cause even mild hyponatremia.

Palatability of two different formulations of urea for the treatment of hyponatremia: A double-blind, randomized, cross-over study

BACKGROUND AND AIMS

Hyponatremia (HN) is the most common disorder of electrolytes encountered in clinical practice. Considering that HN is associated with high morbidity and mortality, it is important to identify treatments for these patients. The therapeutic approaches for HN depend on the severity and the character of the pathology (acute vs. chronic). Among intervention strategies, oral urea represents an effective, safe, and well-tolerated therapeutic approach in the management of chronic hyponatremia. Oral ureal is commonly prepared as a galenic formulation that is usually associated with distaste problems. A double-blind, randomized, cross-over clinical trial was conducted to evaluate and compare the palatability of two different urea formulations: a commercial urea formulation and a galenic one (trial registered on www.isrctn.com, number: ISRCTN18369035).

MATERIALS AND METHODS

Thirty-six healthy subjects (18 female and 18 male, median age 55 years) were enrolled in the study and randomized to consume 7 g of formulation A (commercial formulation) or formulation B (galenic formulation) twice a day away from meals, solubilizing the products in 125 mL of water (T0). After three days of a wash-out, the formulations were crossed-over and consumed twice a day away from meals (T4). After the consumption of products, both in the morning and the evening, participants completed a specific questionnaire to evaluate the products' palatability.

RESULTS

The commercial formulation was globally more appreciated than the galenic one, in terms of smell, taste, and aftertaste. The commercial formulation was better accepted as a potential treatment in 44 % of subjects compared to 14 % of subjects for galenic formulation.

CONCLUSIONS

The clinical trial confirmed the better palatability of the commercial oral urea formulation, containing citrus flavor, which therefore represents a therapeutic strategy that could improve adherence to the therapy in chronic patients with hyponatremia.

Use of Urea for the Syndrome of Inappropriate Secretion of Antidiuretic Hormone: A Systematic Review

Importance

Hyponatremia and the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) are associated with significant mortality and morbidity. The effectiveness and safety of oral urea for SIADH are still debated.

Objective

To evaluate the efficacy and safety of urea for the treatment of SIADH.

Evidence Review

A systematic search of Medline and Embase was conducted for controlled and uncontrolled studies of urea for SIADH in adult patients. The primary outcome was serum sodium concentration after treatment. Secondary outcomes included the proportion of patients with osmotic demyelination syndrome (ODS), intracranial pressure, and resource use such as length of stay.

Findings

Twenty-three studies involving 537 patients with SIADH were included, of which 462 were treated with urea. The pooled mean baseline serum sodium was 125.0 mmol/L (95% CI, 122.6-127.5 mmol/L). The median treatment duration with oral urea was 5 days. Urea increased serum sodium concentration by a mean of 9.6 mmol/L (95% CI, 7.5-11.7 mmol/L). The mean increase in serum sodium after 24 hours was 4.9 mmol/L (95% CI, 0.5-9.3 mmol/L). Adverse events were few, mainly consisting of distaste or dysgeusia, and no case of ODS was reported. Resource use was too infrequently reported to be synthesized.

Conclusions and Relevance

In this systematic review of the use of urea in SIADH and despite the lack of randomized clinical trials, lower-quality evidence was identified that suggests that urea may be an effective, safe, and inexpensive treatment modality that warrants further exploration.

A profile of SGLT-2 inhibitors in hyponatremia: The evidence to date

Hyponatremia is the most common electrolyte disorder in clinical practice, which may lead to life-threatening complications. Several lines of evidence suggest that hyponatremia is associated not only with significant increases in length of stay, cost, and financial burden, but also with increased morbidity and mortality. Hyponatremia is also considered to be a negative prognostic factor in patients with heart failure and cancer. Although multiple therapeutic methods are available for treating hyponatremia, most have some limitations, such as poor compliance, rapid correction of serum Na⁺, other negative side effects and high cost. Given these limitations, identifying novel therapies for hyponatremia is essential. Recent clinical studies have shown that SGLT-2 inhibitors (SGLT 2i) significantly increased serum Na⁺ levels and were well tolerated by patients who underwent this treatment. Therefore, oral administration of SGLT 2i appears to be an effective treatment for hyponatremia. This article will briefly review the etiology of hyponatremia and integrated control of sodium within the kidney, current therapies for hyponatremia, potential mechanisms and efficacy of SGLT 2i for hyponatremia, and the benefits in cardiovascular, cancer, and kidney disease by regulating sodium and water balance.

Hyponatremia and Cancer: From Bedside to Benchside

Hyponatremia is the most common electrolyte disorder encountered in hospitalized patients. This applies also to cancer patients. Multiple causes can lead to hyponatremia, but most frequently this electrolyte disorder is due to the syndrome of inappropriate antidiuresis. In cancer patients, this syndrome is mostly secondary to ectopic secretion of arginine vasopressin by tumoral cells. In addition, several chemotherapeutic drugs induce the release of arginine vasopressin by the hypothalamus. There is evidence that hyponatremia is associated to a more negative outcome in several pathologies, including cancer. Many studies have demonstrated that in different cancer types, both progression-free survival and overall survival are negatively affected by hyponatremia, whereas the correction of serum [Na⁺] has a positive effect on patient outcome. In vitro studies have shown that cells grown in low [Na⁺] have a greater proliferation rate and motility, due to a dysregulation in intracellular signalling pathways. Noteworthy, vasopressin receptors antagonists, which were approved more than a decade ago for the treatment of euvolemic and hypervolemic hyponatremia, have shown unexpected antiproliferative effects. Because of this property, vaptans were also approved for the treatment of polycystic kidney disease. In vitro evidence indicated that this family of drugs effectively counteracts proliferation and invasivity of cancer cells, thus possibly opening a new scenario among the pharmacological strategies to treat cancer.

Treatment Effect of the SGLT2 Inhibitor Empagliflozin on Chronic Syndrome of Inappropriate Antidiuresis: Results of a Randomized, Double-Blind, Placebo-Controlled, Crossover Trial

BACKGROUND

The syndrome of inappropriate antidiuresis (SIAD) is characterized by a reduction of free water excretion with consecutive hypotonic hyponatremia and is therefore challenging to treat. The sodium-glucose cotransporter 2 (SGLT2) inhibitor empagliflozin promotes osmotic diuresis via urinary glucose excretion, likely leading to increased electrolyte free water clearance.

METHODS

In this randomized, double-blind, placebo-controlled, crossover trial, we compared 4-week treatment with empagliflozin 25 mg/d to placebo in outpatients with chronic SIAD-induced hyponatremia. At baseline and after both treatment cycles, patients underwent different assessments including neurocognitive testing (Montreal Cognitive Assessment [MoCA]). The primary end point was the difference in serum sodium levels between treatments.

RESULTS

Fourteen patients, 50% female, with a median age of 72 years (interquartile range [IQR], 65-77), completed the trial. Median serum sodium level at baseline was 131 mmol/L (IQR, 130-132). After treatment with empagliflozin, median serum sodium level rose to 134 mmol/L (IQR, 132-136), whereas no increase was seen with placebo (130 mmol/L; IQR, 128-132), corresponding to a serum sodium increase of 4.1 mmol/L (95% confidence interval [CI], 1.7 to 6.5; P =0.004). Exploratory analyses showed that treatment with empagliflozin led to improved neurocognitive function with an increase of 1.16 (95% CI, 0.05 to 2.26) in the MoCA score. Treatment was well tolerated; no serious adverse events were reported.

CONCLUSION

The SGLT2 inhibitor empagliflozin is a promising new treatment option for chronic SIAD-induced hyponatremia, possibly improving neurocognitive function. Larger studies are needed to confirm the observed treatment effects.

CLINICAL TRIAL REGISTRATION NUMBER

ClinicalTrials.gov NCT03202667.

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