Dose comparison of conivaptan (Vaprisol®) in patients with euvolemic or hypervolemic hyponatremia--efficacy, safety, and pharmacokinetics

A Conspectus of Euvolemic Hyponatremia, Its Various Etiologies, and Treatment Modalities: A Comprehensive Review of the Literature

Hyponatremia is the most prevalent electrolyte imbalance encountered among hospitalized patients, athletes, the elderly, patients with chronic ailments, postoperative patients, and a few asymptomatic individuals. Clinical manifestations of hyponatremia can be diverse, with characteristic neurological symptoms. Depending on in-depth medical history, physical examination (including volume status assessment), laboratory investigation, and drug history, patients can be classified broadly as undergoing hypervolemic, euvolemic, or hypovolemic hyponatremia. However, patients with hypervolemic hyponatremia often present with distinctive signs such as edema or ascites, and the clinical presentation of hypovolemic and euvolemic hyponatremia poses significant challenges for clinicians. The convolution in clinical manifestations of patients is due to the varied etiologies of euvolemic hyponatremia, such as syndrome of inappropriate antidiuretic hormone secretion (SIADH), adrenocortical insufficiency, hypothyroidism, psychogenic polydipsia, different classes of drugs (chemotherapeutics, antipsychotics, antidepressants), endurance exercise events, and reset osmostat syndrome (ROS). The management of hyponatremia depends on the rate of hyponatremia onset, duration, severity of symptoms, levels of serum sodium, and underlying comorbidities. Over the last decade, the clinical understanding of hyponatremia has been scattered due to the introduction of innovative laboratory markers and new drugs. This article will be a conspectus of all the recent advancements in the field of diagnosis, investigations, management, and associations of hyponatremia, along with traditional clinical practices. Subsequently, a holistic overview has been laid out for the clinicians to better understand and identify knowledge deficiencies on this topic.

Effects of Conivaptan versus Mannitol on Post-Ischemic Brain Injury and Edema

Objective

The aim of this study was to compare the effects of conivaptan, an arginine vasopressin antagonist, and mannitol, a sugar alcohol, on cerebral ischemia-induced brain injury and edema in rats.

Materials and Methods

Fifty-eight 8-week-old male Sprague Dawley rats were randomly divided into five groups: control, ischemia-reperfusion (I/R)+saline, I/R+mannitol, I/R+10 mg/ml conivaptan, and I/R+20 mg/ml conivaptan. Cerebral ischemia was induced by common carotid artery occlusion for 30 minutes. Saline, mannitol, or conivaptan were administered intravenously at the onset of reperfusion. Blood and brain tissue samples were taken at the 6th hour of reperfusion. The electrolytes (Na+-K+-Cl-), osmolality, arginine vasopressin, albumin, progranulin (PGRN), neuron-specific enolase (NSE), and myeloperoxidase activity were measured in rat serum samples. Brain frontal/hippocampal sections were stained with hematoxylin-eosin and TUNEL techniques to evaluate histopathological changes.

Results

Statistical analyses revealed that conivaptan caused significant changes in the electrolyte, NSE, and PGRN levels and osmolality when compared with mannitol. Conivaptan treatment showed positive effects on serum biochemistry and tissue histology.

Conclusion

Our findings revealed that conivaptan shows more diuretic activity than mannitol and triggers neither any damages nor edema in the brain tissue. This study may provide beneficial information for the development of treatment strategies for ischemia-related cerebrovascular diseases.

Development and validation of an HPLC-MS/MS method for the determination of arginine-vasopressin receptor blocker conivaptan in human plasma and rat liver microsomes: application to a metabolic stability study

Purpose

To develop and validate a bio-analytical HPLC–MS/MS method for the determination of conivaptan (CVA) an arginine-vasopressin receptor blocker in human plasma and in rat liver microsomes (RLMs).

Methods

Analytes were separated on a reversed phase C18 column (50 mm × 2.1 mm, 1.8 μm). The mobile phase was a mixture of acetonitrile and 10 mM ammonium formate (40:60 v/v, pH 4.0) and was pumped isocratically for 4 min at a flow rate of 0.2 ml/min. Multiple reaction monitoring in positive ionization mode was used for the assay.

Results

The method yielded a linear calibration plot (r²= 0.9977 and 0.9998) over 5–500 ng/ml with a limit of detection at 1.52 and 0.88 ng/ml for human plasma and RLMs, respectively. The reproducibility of detection of CVA in human plasma and RLMs was found to be in an acceptable range.

Conclusion

The method developed in this study is applicable for accurately quantifying CVA in human plasma and rat liver microsomal samples. The optimized procedure was applied to study of metabolic stability of CVA. Conivaptan concentration rapidly decreased in the first 2 min of RLMs incubation and the conversion reached a plateau for the remainder of the incubation period. The in vitro half-life (t_1/2) was estimated at 11.51 min and the intrinsic clearance (CL_in) was 13.8 ± 0.48 ml/min/kg.

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.