Real-World, Non-Interventional, Retrospective Study (SAMPLE) of Tolvaptan in Patients with Hyponatraemia Secondary to the Syndrome of Inappropriate Antidiuretic Hormone Secretion

Low-dose tolvaptan for the treatment of SIADH-associated hyponatremia: a systematic review, meta-analysis, and meta-regression analysis of clinical effectiveness and safety

OBJECTIVE

Tolvaptan at the licensed dose of 15mg effectively treats syndrome of inappropriate antidiuresis (SIAD)-associated hyponatremia. However, concerns about overcorrection and osmotic demyelination syndrome have limited its adoption. We conducted a systematic review and meta-analysis to evaluate the efficacy and safety of lower tolvaptan doses (<15mg) for treating SIAD-associated hyponatremia.

METHODS

We systematically searched MEDLINE, EMBASE, Cochrane CENTRAL, ClinicalTrials.gov, SCOPUS from inception to February 2024. Primary outcomes were change in serum sodium and overcorrection rates. Secondary outcomes included adverse effects, hospital length of stay, and quality of life measures. We conducted meta-analyses using mean differences for efficacy and proportions for safety outcomes, with dose-based subgroup analyses and meta-regression.

RESULTS

From 968 identified papers, 18 studies met inclusion criteria, comprising 495 patients. Initial doses below 15mg increased serum sodium by 7.2 mmol/L (95% CI: 6.0-8.4) within 24 hours. In the 7.5mg subgroup (n=286), the mean increase was 7.8 mmol/L (95% CI: 6.2-9.4). Overcorrection rates were 31% (95% CI: 15-53%) for ≥10 mmol/L and 10% (95% CI: 3-20%) for ≥12 mmol/L rise in 24 hours. In the 3.75mg subgroup, the mean increase was 7.1 mmol/L (95% CI: 4.7-9.6). There was insufficient data to review overcorrection rates. No cases of osmotic demyelination syndrome were reported. Secondary outcome data were insufficient for meta-analysis.

CONCLUSION

Low-dose tolvaptan (3.75-7.5mg) effectively increases serum sodium in SIAD-associated hyponatremia. We recommend initiating tolvaptan at 7.5mg, or 3.75mg in high-risk patients, with close monitoring of sodium levels. These findings support a lower starting dose than currently licensed, though randomized controlled trials are needed to confirm optimal dosing strategies.

Efficacy and Safety of Low-Dose Tolvaptan (7.5 mg) in the Treatment of Inpatient Hyponatremia: A Retrospective Study

OBJECTIVES

The recommended dose of tolvaptan for hyponatremia secondary to the syndrome of inappropriate antidiuretic hormone is 15 mg. We evaluated the efficacy of an initial 7.5 mg dose and determined the frequency where sodium (Na+) correction exceeded safe limits, defined as an increment of ≥10 mmol/L, within the initial 8 or 24 hours of administration.

METHODS

A retrospective review of patients with syndrome of inappropriate antidiuretic hormone treated in a single academic hospital in London. The initial dose was 7.5 mg and the second dose was 7.5 or 15 mg.

RESULTS

One hundred eighty-one patients were included. With the initial dose, the mean Na + increase was 4.54 ± 3.70 mmol/L (P < .0001) after 4-12 hours, with 8.7% demonstrating an increase exceeding 10 mmol/L. Between 18-30 hours, the mean Na + increase was 6.15 ± 3.51 mmol/L (P < .0001), with 19.4% over-correcting. Over-correction was more likely in patients with a pre-dose Na + concentration of ≤127 mmol/L (OR 13.64, 95% CI 1.80-102.95). No cases of osmotic demyelination syndrome were observed. For patients needing a second dose, the increment in Na + concentration showed no significant difference between 7.5 and 15 mg (P = .532).

CONCLUSION

In our view, tolvaptan can be initiated with a 7.5 mg dose, accompanied by Na + monitoring at 12 and 24 hours. If a second dose is necessary, 7.5 mg is comparably effective to a 15 mg dose, depending on the initial response. Further monitoring should include Na + concentration at around 24 hours after the second dose.

Tolvaptan safety in autosomal-dominant polycystic kidney disease; a focus on idiosyncratic drug-induced liver injury liabilities

Tolvaptan is a vasopressin V2 receptor antagonist which has proven to be an effective and mostly well-tolerated agent for the treatment of autosomal-dominant polycystic kidney disease. However, its administration is associated with rare but serious idiosyncratic liver injury, which has warranted a black box warning on the drug labels and frequent monitoring of liver blood tests in the clinic. This review outlines mechanistic investigations that have been conducted to date and constructs a working narrative as an explanation for the idiosyncratic drug-induced liver injury (IDILI) events that have occurred thus far. Potential risk factors which may contribute to individual susceptibility to DILI reactions are addressed, and key areas for future investigative/clinical development are highlighted.

Syndrome of Inappropriate Antidiuresis: From Pathophysiology to Management

Hyponatremia is the most common electrolyte disorder, affecting more than 15% of patients in the hospital. Syndrome of inappropriate antidiuresis (SIAD) is the most frequent cause of hypotonic hyponatremia, mediated by nonosmotic release of arginine vasopressin (AVP, previously known as antidiuretic hormone), which acts on the renal V2 receptors to promote water retention. There are a variety of underlying causes of SIAD, including malignancy, pulmonary pathology, and central nervous system pathology. In clinical practice, the etiology of hyponatremia is frequently multifactorial and the management approach may need to evolve during treatment of a single episode. It is therefore important to regularly reassess clinical status and biochemistry, while remaining alert to potential underlying etiological factors that may become more apparent during the course of treatment. In the absence of severe symptoms requiring urgent intervention, fluid restriction (FR) is widely endorsed as the first-line treatment for SIAD in current guidelines, but there is considerable controversy regarding second-line therapy in instances where FR is unsuccessful, which occurs in around half of cases. We review the epidemiology, pathophysiology, and differential diagnosis of SIAD, and summarize recent evidence for therapeutic options beyond FR, with a focus on tolvaptan, urea, and sodium-glucose cotransporter 2 inhibitors.

Approach to the Patient: Hyponatremia and the Syndrome of Inappropriate Antidiuresis (SIAD)

Hyponatremia is the most common electrolyte disturbance seen in clinical practice, affecting up to 30% of acute hospital admissions, and is associated with significant adverse clinical outcomes. Acute or severe symptomatic hyponatremia carries a high risk of neurological morbidity and mortality. In contrast, chronic hyponatremia is associated with significant morbidity including increased risk of falls, osteoporosis, fractures, gait instability, and cognitive decline; prolonged hospital admissions; and etiology-specific increase in mortality. In this Approach to the Patient, we review and compare the current recommendations, guidelines, and literature for diagnosis and treatment options for both acute and chronic hyponatremia, illustrated by 2 case studies. Particular focus is concentrated on the diagnosis and management of the syndrome of inappropriate antidiuresis. An understanding of the pathophysiology of hyponatremia, along with a synthesis of the duration of hyponatremia, biochemical severity, symptomatology, and blood volume status, forms the structure to guide the appropriate and timely management of hyponatremia. We present 2 illustrative cases that represent common presentations with hyponatremia and discuss the approach to management of these and other causes of hyponatremia.

Using Tolvaptan to Treat Hyponatremia: Results from a Post-authorization Pharmacovigilance Study

Introduction

Hyponatremia is a common condition of varying etiology among hospitalized patients and is associated with adverse outcomes. Treatment to normalize serum sodium is advisable. Tolvaptan received European Union marketing authorization for hyponatremia secondary to the syndrome of inappropriate secretion of antidiuretic hormone (SIADH). Post-marketing pharmacovigilance activities were required to characterize the safety profile of tolvaptan more fully in this population, which is often elderly with a high burden of comorbid illness.

Methods

This was a prospective, observational, multinational, post-authorization pharmacovigilance study (NCT01228682) in seven European countries. Hospitalized patients were enrolled who received tolvaptan for hyponatremia associated with SIADH and consented to data collection. Tolvaptan was initiated and assessments performed at physician discretion per local standards of care. To reflect actual clinical practice, no assessments or procedures were required outside the standard of care. Patients who continued to receive long-term tolvaptan following hospital discharge and provided consent received follow-up from their community physicians.

Results

A total of 252 patients (mean age 70.6 years) enrolled. Mean tolvaptan treatment duration was 139.4 days, median 18.5 (range 1–1130) days; most frequent dose was 15 mg/day (used in 75% of patients). Serum sodium increased from baseline (mean 123.2 mmol/l) during treatment week 1 and remained stable during follow-up, with little difference across doses of 7.5, 15, and 30 mg/day. Hyponatremia symptoms (e.g., confusion, unsteady gait, lethargy) were present in 122/252 (48.4%) patients at pre-treatment baseline, decreasing to 46/252 (18.3%) during treatment. Sixty-two patients (24.6%; mean baseline serum sodium 120 mmol/l) experienced rapid correction of hyponatremia within 72 h. No osmotic demyelination syndrome occurred.

Conclusion

In clinical practice, tolvaptan improved serum sodium and decreased hyponatremia symptoms in hyponatremia secondary to SIADH. Serum sodium should be monitored during treatment to minimize risk of rapid correction.

Trial Registration

Clinicaltrials.gov identifier NCT01228682.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12325-021-01947-9.

Hospitalized patients often experience abnormally low blood sodium levels (hyponatremia), which can cause significant symptoms and poses a serious health risk (Wald et al. in Arch Intern Med 170:294–302, 2010). Yet, increasing sodium levels too rapidly in these patients can unintentionally cause osmotic demyelination syndrome, resulting in long-term neurologic damage or death. Tolvaptan was approved in the European Union to treat one type of hyponatremia caused by a hormonal imbalance known as the syndrome of inappropriate secretion of antidiuretic hormone (SIADH). Tolvaptan effectively increased patient sodium levels in clinical trials, but real-world data are needed to understand tolvaptan treatment more fully in everyday clinical practice. We evaluated patterns of use, efficacy, and safety of tolvaptan in patients treated in hospitals and after discharge for hyponatremia due to SIADH. Tolvaptan was correctly used to treat only hyponatremia caused by SIADH in nearly all of the 252 patients studied. Patient sodium levels increased in the first week of tolvaptan treatment and then stabilized. Hyponatremia symptoms, such as confusion, nausea, tiredness, and dizziness, were present in 48.4% of patients before treatment and in 18.3% after starting tolvaptan. Consistent with earlier studies, some patients (24.6%) experienced excessively rapid correction of hyponatremia. However, no subsequent neurologic problems or deaths were attributed to the rapid correction, which suggests that medical providers were carefully monitoring and managing sodium levels to prevent serious consequences. Our study indicates that tolvaptan is being used safely and effectively to treat hyponatremia due to SIADH in a patient population with complex medical needs.