SIADH-related hyponatremia in hospital day care units: clinical experience and management with tolvaptan

Long-term low-dose tolvaptan efficacy and safety in SIADH

PURPOSE

Tolvaptan, a selective vasopressin V2-receptor antagonist, is approved for the treatment of SIADH-related hyponatremia, but its use is limited. The starting dose is usually 15 mg/day, but recent clinical experience suggests a lower starting dose (<15 mg/day) to reduce the risk of sodium overcorrection. However, long-term low-dose efficacy and safety has not been explored, so far. Aim of our study is to characterize safety and efficacy of long-term SIADH treatment with low-dose Tolvaptan.

METHODS

We retrospectively evaluated 11 patients receiving low-dose Tolvaptan (<15 mg/day) for chronic SIADH due to neurological, idiopathic and neoplastic causes. Plasma sodium levels were measured before and 1, 3, 5, 15 and 30 days after starting Tolvaptan and then at 3-month intervals. Anamnestic and clinical data were collected.

RESULTS

Mean time spanned 27.3 ± 29.8 months (range 6 months-7 years). Mean plasma sodium levels were within normal range 1, 3 and 6 months after starting Tolvaptan as well as after 1, 2, 3, 5 and 7 years of therapy. Neither osmotic demyelination syndrome nor overcorrection were observed. Plasma sodium levels normalization was associated with beneficial clinical effects. Neurological patients obtained seizures disappearance, improvement in neurological picture and good recovery from rehabilitation. Neoplastic patients were able to start chemotherapy and improved their general condition. Patients did not show hypernatremia during long-term follow-up and reported mild thirst and pollakiuria.

CONCLUSIONS

The present study shows that long-term low-dose Tolvaptan is safe and effective in SIADH treatment. No cases of overcorrection were documented and mild side effects were reported.

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

INTRODUCTION

The syndrome of inappropriate antidiuretic hormone secretion (SIADH) is the most common cause of hyponatraemia in hospital inpatients. We present data on treatment setting, patient characteristics, and outcomes for patients treated with tolvaptan for SIADH across a range of real-world settings in Germany and Spain.

METHODS

This was a non-interventional, observational, retrospective chart review study. Management was at the discretion of the treating physician, with tolvaptan prescribed according to local clinical practice. Hospital notes and/or medical charts were reviewed from treatment initiation for 6 weeks. Follow-up data were collected when patients were discharged early. Patients were eligible for inclusion if they were ≥ 18 years of age and had been treated with ≥ 2 doses of tolvaptan for one episode of hyponatraemia secondary to SIADH in 2014.

RESULTS

The Full Analysis Set comprised 100 patients from 8 centres. The mean age of patients was 73.9 years. The primary endpoint of the mean increase in serum sodium level from baseline to hospital discharge, or to final available measurement, was 10.3 mmol/L (SD 6.4; 95% CI 9.0, 11.6), from 123.0 mmol/L (SD 6.0) to 133.3 mmol/L (SD 4.9). Seventy-seven patients (77.0%) achieved sodium normalisation within 6 weeks of tolvaptan initiation. Mean daily dose of tolvaptan was 12.7 mg (SD 9.2), and mean treatment duration 28.0 days (SD 16.5). Tolvaptan at off-label doses (< 15 mg/day) was prescribed to 72 patients at some point. A favourable safety and tolerability profile was reported.

CONCLUSIONS

Tolvaptan was well tolerated and effectively corrected sodium levels in hospitalised adults with hyponatraemia secondary to SIADH in real-world settings. CLINICALTRIALS.

GOV IDENTIFIER

NCT02545101.

Hyponatremia in patients with cancer

PURPOSE OF REVIEW

Hyponatremia is seen commonly in patients with cancer and is associated with increased mortality and morbidity. Understanding the proper diagnosis and therapy of cancer-associated hyponatremia is critical to ensure improved outcomes.

RECENT FINDINGS

The most common cancers associated with hyponatremia are the various forms of lung cancer with incidences approaching 25-45%. The most common causes of hyponatremia in cancer patients are the syndrome of inappropriate antidiuretic hormone secretion [syndrome of inappropriate antidiuretic hormone (ADH)] and volume depletion. Proper diagnosis rests on clinical information supplemented by laboratory studies and is critical to ensure appropriate therapy. In recent years, the development of drugs that specifically antagonize the vasopressin type 2 receptor in the distal tubule have offered targeted and highly effective therapies for syndrome of inappropriate ADH.

SUMMARY

Hyponatremia in cancer patients generally indicates advanced or severe disease but proper therapy that targets the underlying process can improve outcomes.

Hyponatremia in the elderly: challenges and solutions

Decreased serum sodium concentration is a rather frequent electrolyte disorder in the elderly population because of the presence of factors contributing to increased antidiuretic hormone, the frequent prescription of drugs associated with hyponatremia and also because of other mechanisms such as the “tea and toast” syndrome. The aim of this review is to present certain challenges in the evaluation and treatment of hyponatremia in the elderly population and provide practical solutions. Hyponatremia in elderly subjects is mainly caused by drugs (more frequently thiazides and antidepressants), the syndrome of inappropriate antidiuretic hormone secretion (SIAD) or endocrinopathies; however, hyponatremia is multifactorial in a significant proportion of patients. Special attention is needed in the elderly population to exclude endocrinopathies as a cause of hyponatremia before establishing the diagnosis of SIAD, which then requires a stepped diagnostic approach to reveal its underlying cause. The treatment of hyponatremia depends on the type of hyponatremia. Special attention is also needed to correct serum sodium levels at the appropriate rate, especially in chronic hyponatremia, in order to avoid the osmotic demyelination syndrome. In conclusion, both the evaluation and the treatment of hyponatremia pose many challenges in the elderly population.

Managing hyponatremia in lung cancer: latest evidence and clinical implications

Hyponatremia is the most common electrolyte disorder in lung cancer patients. This condition may be related to many causes including incidental medications, concurrent diseases and side effects of antineoplastic treatments or the disease itself. Although not frequently life-threatening, it is usually associated with prolonged hospitalization, delays in scheduled chemotherapy, worsening of patient performance status and quality of life and may also negatively affect treatment response and survival. Most of the available data focus on thoracic tumors, especially small-cell lung cancer (SCLC), where hyponatremia is frequently related to the syndrome of inappropriate secretion of antidiuretic hormone (SIADH). Few studies specifically focus on non-small cell lung cancer (NSCLC) patients. Hyponatremia treatment needs to be personalized based on severity and duration of sodium serum reduction, extracellular fluid volume and etiology. However, literature data highlight the importance of early correction of the serum concentration levels. To achieve this the main options are fluid restriction, hypertonic saline, loop diuretics, isotonic saline, tolvaptan and urea. The aim of this review is to analyze the role of hyponatremia in lung cancer patients, evaluating causes, diagnosis, management and clinical implications.

Electrolyte Disorders Associated with Cancer

Cancer patients frequently suffer electrolyte abnormalities that complicate the management of their condition. The most commonly occurring derangement is hyponatremia, while hypercalcemia, hypokalemia, and hypophosphatemia are also encountered. The etiology of these abnormalities is often identifiable, and early diagnosis and management can prevent delays in necessary anti-cancer therapies.

Role of tolvaptan in the management of hyponatremia in patients with lung and other cancers: current data and future perspectives

Hyponatremia is the most frequently observed electrolyte abnormality in clinical practice, and its frequency is almost double in hospitalized cancer patients. As a subset of cancer, hyponatremia is quite common in lung cancer patients, and it is often coupled with the diagnosis of syndrome of inappropriate antidiuretic hormone secretion. The presence of hyponatremia is consequential in that its presence adversely affects cancer patients’ prognosis and outcomes. Limited data suggest that correcting hyponatremia in lung cancer patients can increase response to anticancer treatment, may help reduce length of hospital stay and cost, and reduce morbidity and mortality. The type of treatment for hyponatremia depends on several factors; the key factors are the duration and severity of neurological symptoms of hyponatremia and the status of extracellular volume. When hyponatremia is caused by syndrome of inappropriate antidiuretic hormone, hypertonic saline is indicated for acute symptomatic cases, whereas fluid restriction is recommended in chronic asymptomatic hyponatremia. The latter allows a slower rate of correction, thus avoiding the dreaded complication of osmotic demyelination syndrome. Fluid restriction is, however, insufficient or impractical, and often the use of pharmacological therapy such as antidiuretic hormone receptor antagonists becomes necessary. Availability of these antagonists as an effective treatment in the management of hyponatremia has been a major breakthrough, and furthermore, its clinical or investigational use in cancer-related hyponatremia may offer a potential opportunity to gain further insights into the prognostic impact of hyponatremia correction on cancer patients’ outcomes. Tolvaptan is a prototype of ADH receptor antagonists that acts at renal tubular levels to increase free water excretion without inducing major systemic electrolyte abnormalities such as hypokalemia or alkalosis. The aim of this paper is to provide a brief review while focusing on cancer hyponatremia; (1) of the epidemiology of hyponatremia and its pathophysiology and diagnostic approaches and (2) of the pharmacokinetics of tolvaptan and its clinical efficacy, safety, and compliance.