Vaptans: A new option in the management of hyponatremia

Trial to control the formation of endolymphatic hydrops from the viewpoint of the water homeostasis of the inner ear

Endolymphatic hydrops, which is one of the pathologic features of Ménière's disease, has been experimentally and clinically confirmed to be influenced by the blood circulation of vasopressin (VP). It is widely acknowledged that VP plays a pivotal role in regulating water homeostasis. It should also be noted that VP is susceptible to a number of external factors, including changes in the environment, dehydration, and fluctuations in atmospheric pressure. Furthermore, VP is a key regulator of the hypothalamic-pituitary-adrenal (HPA) axis. The HPA axis is a significant neuroendocrine system that plays a role in regulating responses to emotional and physical stress, as well as the sleep/wake cycle (circadian rhythm). It seems that VP is changeable via the HPA axis. It may be beneficial to consider pharmacological normalization of VP as a potential approach to controlling Ménière's disease. Nevertheless, measuring 8-Arg-vasopressin (AVP), the most prevalent variant of VP, poses certain challenges for a number of reasons. Copeptin is co-released with AVP, is relatively stable in the posterior pituitary as well as in blood plasma, and is increasingly being used as an AVP surrogate in clinical diagnostics. It is thought that the use of copeptin as a marker for AVP may help to clarify the clinical features of Ménière's disease. In this review, we will consider trials to control the formation of endolymphatic hydrops from the viewpoint of the vasopressin-aquaporin 2 system. Furthermore, we will explore reports on clinical treatment, pharmacological agents, and future prospects.

Therapeutic potential of vasopressin in the treatment of neurological disorders

Vasopressin (VP) is a nonapeptide made of nine amino acids synthesized by the hypothalamus and released by the pituitary gland. VP acts as a neurohormone, neuropeptide and neuromodulator and plays an important role in the regulation of water balance, osmolarity, blood pressure, body temperature, stress response, emotional challenges, etc. Traditionally VP is known to regulate the osmolarity and tonicity. VP and its receptors are widely expressed in the various region of the brain including cortex, hippocampus, basal forebrain, amygdala, etc. VP has been shown to modulate the behavior, stress response, circadian rhythm, cerebral blood flow, learning and memory, etc. The potential role of VP in the regulation of these neurological functions have suggested the therapeutic importance of VP and its analogues in the management of neurological disorders. Further, different VP analogues have been developed across the world with different pharmacotherapeutic potential. In the present work authors highlighted the therapeutic potential of VP and its analogues in the treatment and management of various neurological disorders.

Discovery and Characterization of RGH-122, a Potent, Selective, and Orally Bioavailable V1a Receptor Antagonist

The V1a receptor is a major contributor in mediating the social and emotional effects of arginine-vasopressin (AVP); therefore it represents a promising target in the treatment of several neuropsychiatric conditions. The aim of this research was to design and synthesize novel and selective V1a antagonists with improved in vitro and in vivo profiles. Through optimization and detailed SAR studies, we developed low nanomolar antagonists, and further characterizations led to the discovery of the clinical candidate compound 43 (RGH-122). The CNS activity of the compound was determined in a 3-chamber social preference test of autism in which RGH-122 successfully enhanced social preference with the lowest effective dose of 1.5 mg/kg.

Acute intermittent porphyria: A rare cause of syndrome of inappropriate antidiuretic hormone secretion

A 31-year-old female presented to the emergency department with abdominal pain, vomiting and constipation. Serum sodium levels were recorded at 110 mmol/L on admission, dropping to 96 mmol/L despite fluid restriction. The patient developed hallucinations and required hypertonic saline administration in critical care. Urinary sodium was detected at 149 mmol/L, consistent with syndrome of inappropriate antidiuretic hormone secretion (SiADH). Urinary porphyrins were also raised, consistent with a diagnosis of acute intermittent porphyria with SiADH as a complication.

Arginine vasopressin hormone receptor antagonists in experimental autoimmune encephalomyelitis rodent models: A new approach for human multiple sclerosis treatment

Multiple sclerosis (MS) is a chronic demyelinating and neurodegenerative disease that affects the central nervous system. MS is a heterogeneous disorder of multiple factors that are mainly associated with the immune system including the breakdown of the blood-brain and spinal cord barriers induced by T cells, B cells, antigen presenting cells, and immune components such as chemokines and pro-inflammatory cytokines. The incidence of MS has been increasing worldwide recently, and most therapies related to its treatment are associated with the development of several secondary effects, such as headaches, hepatotoxicity, leukopenia, and some types of cancer; therefore, the search for an effective treatment is ongoing. The use of animal models of MS continues to be an important option for extrapolating new treatments. Experimental autoimmune encephalomyelitis (EAE) replicates the several pathophysiological features of MS development and clinical signs, to obtain a potential treatment for MS in humans and improve the disease prognosis. Currently, the exploration of neuro-immune-endocrine interactions represents a highlight of interest in the treatment of immune disorders. The arginine vasopressin hormone (AVP) is involved in the increase in blood−brain barrier permeability, inducing the development and aggressiveness of the disease in the EAE model, whereas its deficiency improves the clinical signs of the disease. Therefore, this present review discussed on the use of conivaptan a blocker of AVP receptors type 1a and type 2 (V1a and V2 AVP) in the modulation of immune response without completely depleting its activity, minimizing the adverse effects associated with the conventional therapies becoming a potential therapeutic target in the treatment of patients with multiple sclerosis.

Management of Hyponatremia in Heart Failure: Practical Considerations

Hyponatremia is commonly encountered in the setting of heart failure, especially in decompensated, fluid-overloaded patients. The pathophysiology of hyponatremia in patients with heart failure is complex, including numerous mechanisms: increased activity of the sympathetic nervous system and the renin-angiotensin-aldosterone system, high levels of arginine vasopressin and diuretic use. Symptoms are usually mild but hyponatremic encephalopathy can occur if there is an acute decrease in serum sodium levels. It is crucial to differentiate between dilutional hyponatremia, where free water excretion should be promoted, and depletional hyponatremia, where administration of saline is needed. An inappropriate correction of hyponatremia may lead to osmotic demyelination syndrome which can cause severe neurological symptoms. Treatment options for hyponatremia in heart failure, such as water restriction or the use of hypertonic saline with loop diuretics, have limited efficacy. The aim of this review is to summarize the principal mechanisms involved in the occurrence of hyponatremia, to present the main guidelines for the treatment of hyponatremia, and to collect and analyze data from studies which target new treatment options, such as vaptans.

Vasopressin receptor antagonists: a patent summary (2018-2022)

INTRODUCTION

Arginine-vasopressin hormone (AVP) is a key regulator in many essential physiological processes. The effect of AVP is mediated through three receptors within the body, these are the G protein-coupled vasopressin receptors, namely V1a, V1b (also called V3), and V2. Numerous studies investigated the role of these receptors in certain pathological conditions; therefore, stimulation or inhibition of these receptors may be a treatment option in these diseases.

AREAS COVERED

In this manuscript, the authors summarize recent patent activity (2018-2022) associated with vasopressin receptor antagonists (selective V1a or V2, and dual-acting V1a/V2), focusing mostly on chemical structures, their modifications, and potential clinical applications. Patent search was carried out using SciFinder, Espacenet, Patentscope, Cortellis Competitive Intelligence, and Derwent Innovation databases.

EXPERT OPINION

In recent years, vasopressin receptor antagonists have been in the spotlight of drug discovery, especially V1a selective molecules. Publishing balovaptan as a possible treatment for autism spectrum disorder (ASD), greatly increased the interest in CNS-acting vasopressin antagonists. In addition, peripherally active selective V2 and dual-acting V1a/V2 antagonists have also been developed. Although clinical trials were unsuccessful in many cases, there is still potential in the research of vasopressin receptor antagonists as shown by several currently ongoing clinical trials.

Tolvaptan Response in a Hyponatremic Newborn with Syndrome of Inappropriate Secretion of Antidiuretic Hormone

The use of tolvaptan to treat both euvolemic and hypervolemic hyponatremia has rapidly increased in recent years. However, data on its effects on children, especially newborns and infants, are limited. Here, we present a newborn who developed syndrome of inappropriate secretion of antidiuretic hormone following an intracranial hematoma drainage operation who was unresponsive to conventional treatments. The infant was successfully treated with tolvaptan, a competitive inhibitor of the vasopressin V2 receptor.

Regulation of Serum Sodium Levels during Chemotherapy Using Selective Arginine Vasopressin V2-Receptor Antagonist Tolvaptan in a Four-Year-Old Girl with a Suprasellar Germ Cell Tumor

There are limited reports on the use of tolvaptan for syndrome of inappropriate antidiuretic hormone secretion (SIADH) in children. Managing serum sodium levels in SIADH patients during chemotherapy is often difficult because of the need for massive fluid infusions. We report the course of the use of tolvaptan for the treatment of hyponatremia during chemotherapy in a four-year-old girl with a suprasellar germ cell tumor. The patient was a Japanese girl who presented with left ptosis with a mass in the pituitary gland and cavernous sinus. She was diagnosed with an intermediate-grade germ cell tumor and was treated with carboplatin and etoposide combination chemotherapy. She developed hyponatremia due to SIADH caused by intravenous infusion therapy before chemotherapy. Subsequently, tolvaptan (3.25 mg; 0.20 mg/kg/dose) was administered orally to control serum sodium levels. After 4 h of administration, a marked increase in urine volume of up to 15 mL/kg/h was observed, and serum sodium level increased from 126 to 138 mEq/L after 10 h of tolvaptan administration, followed by a decrease in urine volume. The use of tolvaptan in pediatric patients with SIADH who require intravenous hydration during chemotherapy can be useful for the management of serum sodium balance.

A Case Report of Severe Hyponatremia Secondary to Coronavirus Disease 2019 Viral Pneumonia

As of December 2020, the coronavirus disease 2019 (COVID-19) pandemic has resulted in 82.2 million cases worldwide. We report the case of a 69-year-old South Asian female with a history of hypertension, hypothyroidism, meningiomatosis, and urinary incontinence who contracted COVID-19 and developed severe hyponatremia. She was initially medically managed with antibiotics, anti-parasitics, anti-coagulants, and steroids. After experiencing breathlessness, chest discomfort, high systolic blood pressure, and tachycardia, she was admitted and diagnosed with post-COVID pneumonia, and was conservatively treated with steroids. She showed improvement, and was discharged upon being declared hemodynamically stable. While the patient was at home, she experienced periods of breathlessness and acral edema. This case raises the question of the correlation between hyponatremia and COVID-19, especially in regards to symptomatic presentations, including altered mental status, headache, and nausea. As there are limited studies that show severe electrolyte disorders leading to mortality, more research is needed to understand hyponatremia in cases with COVID-19.

Hyponatraemia and hypernatraemia: Disorders of Water Balance in Neurosurgery

Disorders of tonicity, hyponatraemia and hypernatraemia, are common in neurosurgical patients. Tonicity is sensed by the circumventricular organs while the volume state is sensed by the kidney and peripheral baroreceptors; these two signals are integrated in the hypothalamus. Volume is maintained through the renin-angiotensin-aldosterone axis, while tonicity is defended by arginine vasopressin (antidiuretic hormone) and the thirst response. Edelman found that plasma sodium is dependent on the exchangeable sodium, potassium and free-water in the body. Thus, changes in tonicity must be due to disproportionate flux of these species in and out of the body. Sodium concentration may be measured by flame photometry and indirect, or direct, ion-sensitive electrodes. Only the latter method is not affected by changes in plasma composition. Classification of hyponatraemia by the volume state is imprecise. We compare the tonicity of the urine, given by the sodium potassium sum, to that of the plasma to determine the renal response to the dysnatraemia. We may then assess the activity of the renin-angiotensin-aldosterone axis using urinary sodium and fractional excretion of sodium, urate or urea. Together, with clinical context, these help us determine the aetiology of the dysnatraemia. Symptomatic individuals and those with intracranial catastrophes require prompt treatment and vigilant monitoring. Otherwise, in the absence of hypovolaemia, free-water restriction and correction of any reversible causes should be the mainstay of treatment for hyponatraemia. Hypernatraemia should be corrected with free-water, and concurrent disorders of volume should be addressed. Monitoring for overcorrection of hyponatraemia is necessary to avoid osmotic demyelination.

Modern trends in diuretics development

Diuretics are the first-line therapy for widespread cardiovascular and non-cardiovascular diseases. Traditional diuretics are commonly prescribed for treatment in patients with hypertension, edema and heart failure, as well as with a number of kidney problems. They are diseases with high mortality, and the number of patients suffering from heart and kidney diseases is increasing year by year. The use of several classes of diuretics currently available for clinical use exhibits an overall favorable risk/benefit balance. However, they are not devoid of side effects. Hence, pharmaceutical researchers have been making efforts to develop new drugs with a better pharmacological profile. High-throughput screening, progress in protein structure analysis and modern methods of chemical modification have opened good possibilities for identification of new promising agents for preclinical and clinical testing. In this review, we provide an overview of the medicinal chemistry approaches toward the development of small molecule compounds showing diuretic activity that have been discovered over the past decade and are interesting drug candidates. We have discussed promising natriuretics/aquaretics/osmotic diuretics from such classes as: vasopressin receptor antagonists, SGLT2 inhibitors, urea transporters inhibitors, aquaporin antagonists, adenosine receptor antagonists, natriuretic peptide receptor agonists, ROMK inhibitors, WNK-SPAK inhibitors, and pendrin inhibitors.

Sex Differences in the Regulation of Vasopressin and Oxytocin Secretion in Bile Duct-Ligated Rats

INTRODUCTION

Hyponatremia due to elevated arginine vasopressin (AVP) secretion increases mortality in liver failure patients. No previous studies have addressed sex differences in hyponatremia in liver failure animal models.

OBJECTIVE

This study addressed this gap in our understanding of the potential sex differences in hyponatremia associated with increased AVP secretion.

METHODS

This study tested the role of sex in the development of hyponatremia using adult male, female, and ovariectomized (OVX) female bile duct-ligated (BDL) rats.

RESULTS

All BDL rats had significantly increased liver to body weight ratios compared to sham controls. Male BDL rats had hyponatremia with significant increases in plasma copeptin and FosB expression in supraoptic AVP neurons compared to male shams (all p < 0.05; 5-7). Female BDL rats did not become hyponatremic or demonstrate increased supraoptic AVP neuron activation and copeptin secretion compared to female shams. Plasma oxytocin was significantly higher in female BDL rats compared to female sham (p < 0.05; 6-10). This increase was not observed in male BDL rats. Ovariectomy significantly decreased plasma estradiol in sham rats compared to intact female sham (p < 0.05; 6-10). However, circulating estradiol was significantly elevated in OVX BDL rats compared to the OVX and female shams (p < 0.05; 6-10). Adrenal estradiol, testosterone, and dehydroepiandrosterone (DHEA) were measured to identify a possible source of circulating estradiol in OVX BDL rats. The OVX BDL rats had significantly increased adrenal estradiol along with significantly decreased adrenal testosterone and DHEA compared to OVX shams (all p < 0.05; 6-7). Plasma osmolality, hematocrit, copeptin, and AVP neuron activation were not significantly different between OVX BDL and OVX shams. Plasma oxytocin was significantly higher in OVX BDL rats compared to OVX sham.

CONCLUSIONS

Our results show that unlike male BDL rats, female and OVX BDL rats did not develop hyponatremia, supraoptic AVP neuron activation, or increased copeptin secretion compared to female shams. Adrenal estradiol might have compensated for the lack of ovarian estrogens in OVX BDL rats.

Efficiency of Single Dose of Tolvaptan Treatment During the Triphasic Episode After Surgery for Craniopharyngioma

Inappropriate antidiuretic hormone syndrome (SIADH) may develop after intracranial surgery. SIADH in the pediatric age group is usually encountered in patients with an intracranial mass both before and after surgery. Fluid restriction is the standard therapy in SIADH. However, a resistant, hyponatremic pattern may be encountered in some cases. Vaptans have been recently introduced for treatment of hyponatremia due to SIADH. There is inadequate data concerning tolvaptan treatment in pediatric patients. We present a 13 year-old female with SIADH of triphasic episode who was transferred to our clinic after surgery for craniopharyngioma. Resistant hyponatremia did not resolve despite fluid restriction and hypertonic saline support. The patient responded rapidly to a single dose of tolvaptan, with no adverse effect, which resulted in successful control of her SIADH.

Tolvaptan Use to Treat SIADH in a Child

Hyponatremia is one of the most common electrolyte abnormalities encountered in the clinical setting in hospitalized patients. The syndrome of inappropriate antidiuretic hormone secretion (SIADH) is the leading cause of hyponatremia in most of these cases. While fluid restriction, hypertonic saline infusion, diuretics, and the treatment of underlying conditions constitute the first line of treatment of SIADH, in refractory cases, and especially for pediatric patients, there seems not to be any other choice for treatment. Tolvaptan, although its use in pediatric patients is still very limited, might be an attractive treatment option for correction of hyponatremia due to SIADH. Here we present a pediatric case of SIADH that was resistant to treatment with fluid restriction and hypertonic saline infusion and was treated successfully with tolvaptan. Tolvaptan could be a good, safe, and effective treatment option in pediatric SIADH cases that are resistant to treatment. However, the dosage should be titrated carefully.

Unveiling some FDA-approved drugs as inhibitors of the store-operated Ca2+ entry pathway

The store-operated calcium entry (SOCE) pathway is an important route for generating cytosolic Ca²⁺ signals that regulate a diverse array of biological processes. Abnormal SOCE seem to underlie several diseases that notably include allergy, inflammation and cancer. Therefore, any modulator of this pathway is likely to have significant impact in cell biology under both normal and abnormal conditions. In this study, we screened the FDA-approved drug library for agents that share significant similarity in 3D shape and surface electrostatics with few, hitherto best known inhibitors of SOCE. This has led to the identification of five drugs that showed dose-dependent inhibition of SOCE in cell-based assay, probably through interacting with the Orai1 protein which effectively mediates SOCE. Of these drugs, leflunomide and teriflunomide could suppress SOCE significantly at clinically-relevant doses and this provides for an additional mechanism towards the therapeutic utility of these drugs as immunosuppressants. The other three drugs namely lansoprazole, tolvaptan and roflumilast, were less potent in suppressing SOCE but were more selective and thus they may serve as novel scaffolds for future development of new, more efficacious SOCE inhibitors.

Tolvaptan Treatment in Children with Chronic Hyponatremia due to Inappropriate Antidiuretic Hormone Secretion: A Report of Three Cases

Hyponatremia is the most common electrolyte disorder among hospitalized patients and it is sometimes considered as a poor outcome predictor. Its correction is thus indicated, even in asymptomatic patients. The conventional treatment consists of fluid restriction in presence of euvolemia or hypervolemia; loop diuretics are used in some hypervolemic conditions such as cardiac heart failure, liver cirrhosis and nephrotic syndrome, while intravenous isotonic or hypertonic solutions are administered in hypovolemic conditions. The utilization of demeclocycline and urea is not indicated in pediatric ages due to lack of data on their toxicity and poor tolerance. Recently, a new therapeutic option has been developed, a class of non-peptide arginine vasopressin receptor antagonists called vaptans. Tolvaptan is the only such agent approved in Europe for the treatment of hyponatremia caused by syndrome of inappropriate antidiuretic hormone secretion (SIADH) in adults. In USA, tolvaptan and conivaptan have been approved for treatment of euvolemic and hypervolemic hyponatremia. Few data are so far available in paediatric patients, since only one trial has been registered in Europe which includes children and adolescents, but this trial is still ongoing. Here, we report three children with chronic hyponatremia due to SIADH in which tolvaptan has been used successfully.

Cardiorenal Syndrome: Role of Arginine Vasopressin and Vaptans in Heart Failure

Heart and kidney failure continued to be of increasing prevalence in today's society, and their comorbidity has synergistic effect on the morbidity and mortality of patients. Cardiorenal syndrome (CRS) is a complex disease with multifactorial pathophysiology. Better understanding of this pathophysiological network is crucial for the successful intervention to prevent advancement of the disease process. One of the major factors in this process is neurohormonal activation, predominantly involving renin-angiotensin-aldosterone system (RAAS) and arginine vasopressin (AVP). Heart failure causes reduced cardiac output/cardiac index (CO/CI) and fall in renal perfusion pressures resulting in activation of baroreceptors and RAAS, respectively. Activated baroreceptors and RAAS stimulate the release of AVP (non-osmotic pathway), which acts on V₂ receptors located in the renal collecting ducts, causing fluid retention and deterioration of heart failure. Effective blockade of AVP action on V₂ receptors has emerged as a potential treatment option in volume overload conditions especially in the setting of hyponatremia. Vasopressin receptor antagonists (VRAs), such as vaptans, are potent aquaretics causing electrolyte-free water diuresis without significant electrolyte abnormalities. Vaptans are useful in hypervolemic hyponatremic conditions like heart failure and liver cirrhosis, and euvolemic hyponatremic conditions like syndrome of inappropriate anti-diuretic hormone secretion. Tolvaptan and conivaptan are pharmaceutical agents that are available for the treatment of these conditions.

Benefit of tolvaptan in the management of hyponatraemia in patients with diuretic-refractory congestive heart failure: the SEMI-SEC project

Aims

Hyponatraemia is an electrolyte disorder that occurs in advanced congestive heart failure (HF) and worsens prognosis. We explored the usefulness of tolvaptan, which has shown promising results in the treatment of this condition.

Methods and results

This study is based on a retrospective national registry (2011–15) of patients hospitalized with refractory HF and hyponatraemia who agreed to receive tolvaptan when standard treatment was ineffective. The benefit of tolvaptan was analysed according to the following criteria: normalization ([Na⁺] ≥ 135 mmol/L) or increased sodium levels [Na⁺] ≥ 4 mEq/L on completion of treatment, and increase in urine output by 300 or 500 mL at 48 h. Factors associated with tolvaptan benefit were explored. A total of 241 patients were included, 53.9% of whom had ejection fraction <40%. All patients received concomitant loop diuretics. Initial tolvaptan dose was 17.2 ± 6.1 mg, and end dose was 26.4 ± 23.2 mg (duration 7.8 ± 8.6 days). Serum sodium concentrations increased significantly at 24–48 h, from 126.5 ± 6.2 mEq/L at baseline to 134.1 ± 6.1 mEq/L at the end of treatment (P < 0.0001). Weight fell by ~5 kg before discharge (P < 0.0001) and urine output increased 1.3‐fold (P < 0.0001). Normal sodium levels and/or increases of 500 mL in urine output were achieved by 90.8% of patients (35.7% achieved both) and 94.8% increased to [Na⁺] ≥ 4 mEq/L and/or +300 mL in urine output (54.4% both).

Conclusions

An increase in sodium levels and/or improvement in urine output was observed in patients admitted for HF and refractory hyponatraemia under tolvaptan treatment. Tolvaptan may be useful in this setting, in which no effective proven alternatives are available.

Conivaptan, a Selective Arginine Vasopressin V1a and V2 Receptor Antagonist Attenuates Global Cerebral Edema Following Experimental Cardiac Arrest via Perivascular Pool of Aquaporin-4

BACKGROUND

Cerebral edema is a major cause of mortality following cardiac arrest (CA) and cardiopulmonary resuscitation (CPR). Arginine vasopressin (AVP) and water channel aquaporin-4 (AQP4) have been implicated in the pathogenesis of CA-evoked cerebral edema. In this study, we examined if conivaptan, a V1a and V2 antagonist, attenuates cerebral edema following CA/CPR in wild type (WT) mice as well as mice with targeted disruption of the gene encoding α-syntrophin (α-syn(-/-)) that demonstrate diminished perivascular AQP4 pool.

METHODS

Isoflurane-anesthetized adult male WT C57Bl/6 and α-syn(-/-) mice were subjected to 8 min CA/CPR and treated with either bolus IV injection (0.15 or 0.3 mg/kg) followed by continuous infusion of conivaptan (0.15 mg/kg/day or 0.3 mg/kg/day), or vehicle infusion for 48 h. Serum osmolality, regional brain water content, and blood-brain barrier (BBB) disruption were determined at the end of the experiment. Sham-operated mice in both strains served as controls.

RESULTS

Treatment with conivaptan elevated serum osmolality in a dose-dependent manner. In WT mice, conivaptan at 0.3 mg dose significantly attenuated regional water content in the caudoputamen (81.0 ± 0.5 vs. 82.5 ± 0.4% in controls; mean ± SEM) and cortex (78.8 ± 0.2 vs. 79.4 ± 0.2% in controls), while conivaptan at 0.15 mg was not effective. In α-syn(-/-) mice, conivaptan at 0.3 mg dose did not attenuate water content compared with controls. Conivaptan (0.3 mg/kg/day) attenuated post-CA BBB disruption at 48 h in WT mice but not in α-syn(-/-) mice.

CONCLUSIONS

Continuous IV infusion of conivaptan attenuates cerebral edema and BBB disruption following CA. These effects of conivaptan that are dependent on the presence of perivascular pool of AQP4 appear be mediated via its dual effect on V1 and V2 receptors.

Efficacy of oral tolvaptan versus 3% hypertonic saline for correction of hyponatraemia in post-operative patients

Background and Aims:

Hyponatraemia is frequent in post-operative patients and may be corrected with hypertonic saline (HTS). Oral tolvaptan is used to treat hypervolaemic or euvolaemic hyponatraemia. This study was performed to assess the efficacy of oral tolvaptan in correcting postoperative hyponatraemia compared to HTS.

Methods:

This prospective, randomised study was conducted in 40 symptomatic patients with serum sodium level ≤130 mEq/L. In Group H (n = 20), 3% HTS was infused at 20–30 mL/h aiming for correction of 6 mEq/L/day. Group T received oral tolvaptan 15 mg on the 1^st day. If daily correction was <4 mEq/L, the dose was increased by 15 mg/day to a maximum of 45 mg. The primary outcome was serum sodium concentration 48 hours after starting treatment. Paired t-test was used to compare changes in sodium levels.

Results:

Baseline sodium and values at 12, 24 and 48 h were comparable in both groups. At 72 h, Group T had significantly higher sodium levels as compared to Group H (133.4 ± 1.9 vs. 131.3 ± 2.4 mEq/L). Intragroup analysis had shown a significant increase in sodium levels from baseline values in both groups at 12, 24, 48 and 72 h. Group H had a significantly lower potassium level and lower negative fluid balance on day 3.

Conclusion:

Oral tolvaptan and 3% HTS were equally effective in correcting hyponatraemia at 48 hours, but serum sodium levels were higher at 72 hours after oral tolvaptan.

Tolvaptan use during hyperhydration in paediatric intracranial lymphoma with SIADH

An 11-year-old boy developed severe syndrome of inappropriate antidiuretic hormone secretion (SIADH) after diagnosis of an intracranial B-cell lymphoma. His sodium levels dropped to 118-120 mmol/L despite 70% fluid restriction. For chemotherapy, he required hyperhydration, which posed a challenge because of severe hyponatraemia. Tolvaptan is an oral, highly selective arginine vasopressin V2-receptor antagonist, which has been licensed in adults for the management of SIADH and has been used in treating paediatric heart failure. Tolvaptan gradually increased sodium levels and allowed liberalisation of fluid intake and hyperhydration. Tolvaptan had profound effects on urinary output in our patient with increases up to 8 mL/kg/h and required close monitoring of fluid balance, frequent sodium measurements and adjustments to intake. After hyperhydration, tolvaptan was stopped, and the lymphoma went into remission with reversal of SIADH. We report one of the first uses of tolvaptan in a child with SIADH, and it was an effective and safe treatment to manage severe SIADH when fluid restriction was not possible or effective. However, meticulous monitoring of fluid balance and sodium levels and adjustments of fluid intake are required to prevent rapid sodium changes.

LEARNING POINTS

Tolvaptan can be used in paediatric patients with SIADH to allow hyperhydration during chemotherapy.Tolvaptan has profound effects on urinary output and meticulous monitoring of fluid balance and sodium 
levels is therefore warranted.Tolvaptan was well tolerated without significant side effects.

Do vasopressin V2 receptor antagonists benefit cirrhotics with refractory ascites?

Hyponatremia is a frequent complication of advanced cirrhosis with ascites associated with increased morbidity and mortality. It is caused by an impairment in the renal capacity to eliminate solute-free water and is considered to be related to persistent secretion of vasopressin despite low serum osmolality. This nonosmotic release of vasopressin is mediated by the autonomic nervous system, which senses the underfilling of arterial vascular component. This reduction of effective arterial blood volume is closely related to the development of ascites. Although the short-time effects of vasopressin V2 receptor antagonists (vaptans) on hyponatremia and ascites have been repeatedly reported, their effects on the long-term management of cirrhotic ascites have not been established yet. Considering that their effects on water diuresis and their safety are limited by severe underfilling state of patients, cautious approaches with adequate monitoring are needed to advanced cirrhosis. Proper indication, adequate doses and new possibility of combination therapy should be explored in the future controlled study. As hyponatremia is frequent obstacle to ascites management, judicious combination with low-dose diuretics may decrease the incidence of refractory ascites. Although vaptans show much promise in the treatment of advanced cirrhosis, the problem of high cost should be solved for the future.

Effectiveness of single dose conivaptan for correction of hyponatraemia in post-operative patients following major head and neck surgeries

Background and Aims:

Conivaptan, a vasopressin receptor antagonist, is commonly used for the treatment of euvolaemic, hypervolaemic hyponatraemia. Usually, an intravenous (IV) bolus followed by infusion is administered for many days. We decided to assess the effectiveness of single dose conivaptan for correction of hyponatraemia in post-operative patients.

Methods:

This was a prospective, randomised trial conducted in 40 symptomatic post-operative Intensive Care Unit (ICU) patients with a serum sodium level of ≤130 mEq/L. Group A patients received IV conivaptan 20 mg over 30 min, whereas in group B infusion of 3% hypertonic saline was started as an infusion at the rate of 20–30 ml/h. Serum sodium levels were measured at 12, 24, 48 and 72 h and the daily fluid balance was measured for 3 days. The Chi-square test, Wilcoxon signed rank test and Mann-Whitney tests were used as applicable.

Results:

The serum sodium levels before initiating treatment were comparable between groups. However, subsequent sodium levels at 12, 24 and 48 h showed significantly high values in group A. Though at 72 h the mean sodium value was high in group A, it was not statistically significant. Group A showed a significantly high fluid loss on day 1, 2 and 3. The mean volume of hypertonic saline required in group B showed a steady decline from day 1 to 3 and only 13 patients required hypertonic saline on the 3^rd day.

Conclusion:

Single dose conivaptan is effective in increasing serum sodium levels in post-operative ICU patients up to 72 h associated with a significant negative fluid balance.

Syndrome of inappropriate antidiuretic hormone secretion and cerebral/renal salt wasting syndrome: similarities and differences

Hyponatremia (sodium levels of <135 mEq/L) is one of the most common electrolyte imbalances in clinical practice, especially in patients with neurologic diseases. Hyponatremia can cause cerebral edema and brain herniation; therefore, prompt diagnosis and proper treatment is important in preventing morbidity and mortality. Among various causes of hyponatremia, diagnosing syndrome of inappropriate antidiuretic hormone secretion (SIADH) and cerebral/renal salt wasting syndrome (C/RSW) is difficult due to many similarities. SIADH is caused by excess of renal water reabsorption through inappropriate antidiuretic hormone secretion, and fluid restriction is the treatment of choice. On the other hand, C/RSW is caused by natriuresis, which is followed by volume depletion and negative sodium balance and replacement of water and sodium is the mainstay of treatment. Determinating volume status in hyponatremic patients is the key point in differential between SIADH and C/RSW. However, in most situations, differential diagnosis of these two diseases is difficult because they overlap in many clinical and laboratory aspects, especially to assess differences in volume status of these patients. Although distinction between the SIADH and C/RSW is difficult, improvement of hypouricemia and an increased fractional excretion of uric acid after the correction of hyponatremia in SIADH, not in C/RSW, may be one of the helpful points in discriminating the two diseases. In this review, we compare these two diseases regarding the pathophysiologic mechanisms, diagnosis, and therapeutic point of view.

Hyponatremia in the neurocritical care patient: An approach based on current evidence

In the neurocritical care setting, hyponatremia is the commonest electrolyte disorder, which is associated with significant morbimortality. Cerebral salt wasting and syndrome of inappropriate antidiuretic hormone have been classically described as the 2 most frequent entities responsible of hyponatremia in neurocritical care patients. Nevertheless, to distinguish between both syndromes is usually difficult and useless as volume status is difficult to be determined, underlying pathophysiological mechanisms are still not fully understood, fluid restriction is usually contraindicated in these patients, and the first option in the therapeutic strategy is always the same: 3% hypertonic saline solution. Therefore, we definitively agree with the current concept of "cerebral salt wasting", which means that whatever is the etiology of hyponatremia, initially in neurocritical care patients the treatment will be the same: hypertonic saline solution.

Outpatient management of chronic heart failure

INTRODUCTION

Heart failure (HF) treatment attracts a share of intensive research because of its poor HF prognosis. In the past decades, the prognosis of HF has improved considerably, mainly as a consequence of the progress that has been made in the pharmacological management of HF.

AREAS COVERED

This article reviews the outpatient pharmacological management of chronic HF due to left ventricular systolic dysfunction and offers recommendations on the use of various drugs. In addition, the present article attempts to provide practical therapeutic algorithms based on current clinical strategies.

EXPERT OPINION

Continued research directed toward identifying factors associated with high pharmacotherapy guideline adherence and understanding of variants that influence response to drugs will hopefully halt or reverse the major pathophysiological mechanisms involved in this syndrome.

Role of vaptans in the management of hydroelectrolytic imbalance in liver cirrhosis

Ascites and hyponatremia are the most common complications in patients with liver cirrhosis and develop as a consequence of a severe impairment of liver function and portal hypertension. Increasing evidences support the central role of renal function alterations in the pathogenesis of hydroelectrolytic imbalances in cirrhotic patients, thus implying a dense cross-talk between liver and kidney in the systemic and splanchnic vascular homeostasis in such subjects. Since Arginin Vasopressin (AVP) hyperincretion occurs at late stage of cirrhosis and plays an important role in the development of refractory ascites, dilutional hyponatremia and finally hepato-renal syndrome, selective antagonists of AVP receptors V₂ (vaptans) have been recently introduced in the therapeutic algorithm of advanced cirrhotic patients. Despite the promising results of earlier phase-two studies, randomized controlled trials failed to find significant results in terms of efficacy of such drugs both in refractory ascites and hyponatremia. Moreover, concerns on their safety profile arise, due to the number of potentially severe side effects of vaptans in the clinical setting, such as hypernatremia, dehydration, renal impairment, and osmotic demyelination syndrome. More robust data from randomized controlled trials are needed in order to confirm the potential role of vaptans in the management of advanced cirrhotic patients.

Treatment of stroke related refractory brain edema using mixed vasopressin antagonism: a case report and review of the literature

Background

Elevated intracranial pressure from cerebral edema is the major cause of early mortality in acute stroke. Current treatment strategies to limit cerebral edema are not particularly effective. Some novel anti-edema measures have shown promising early findings in experimental stroke models. Vasopressin antagonism in stroke is one such target which has shown some encouraging preliminary results. The aim of this report is to highlight the potential use of vasopressin antagonism to limit cerebral edema in patients after acute stroke.

Case presentation

A 57-year-old Caucasian man with new onset diplopia was diagnosed with vertebral artery aneurysm extending into the basilar circulation. He underwent successful elective vertebral artery angioplasty and coiling of the aneurysm. In the immediate post-operative period there was a decline in his neurological status and brain imaging revealed new midbrain and thalamic hemorrhage with surrounding significant brain edema. Treatment with conventional anti-edema therapy was initiated with no significant clinical response after which conivaptan; a mixed vasopressin antagonist was started. Clinical and radiological evaluation following drug administration showed rapid clinical improvement without identification of significant adverse effects.

Conclusions

The authors have successfully demonstrated the safety and efficacy of using mixed vasopressin antagonist in treatment of stroke related brain edema, thereby showing its promise as an alternative anti-edema agent. Preliminary findings from this study suggest mixed vasopressin antagonism may have significant utility in the management of cerebral edema arising from cerebrovascular accident. Larger prospective studies are warranted to explore the role of conivaptan in the treatment of brain edema and neuroprotection.

Tolvaptan

Hyponatremia is a common and often under-recogonised clinical problem in oncologic practice. The recogonition of the cause of hyponatremia and initiation of appropriate and timely intervention can prevent morbidity and improve treatment tolerance. This drug review aims at discussing the currently approved oral vaptanagent Tolvaptan. Vaptans including Tolvaptan act as "aquaretic" agents cousing excretion of water while retaining the sodium. Administration of this agent for prescribed periods result in improvement of serum sodium levels. The drug can be used in many clinical situations resulting in hyponatremia including congestive heart failure, cirrhosis and syndrome of inappropriate ADH secretion (SIADH) including SIADH related to malignancies.