Safety and Efficacy of Vaptans in the Treatment of Hyponatremia from Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH): A Systematic Review and Meta-Analysis

The utilization of vasopressin receptor antagonists, known as vaptans, in the management of hyponatremia among patients afflicted with the syndrome of inappropriate antidiuretic hormone (SIADH) remains a contentious subject. This meta-analysis aimed to evaluate the safety and efficacy of vaptans for treating chronic hyponatremia in adult SIADH patients. Clinical trials and observational studies were identified by a systematic search using MEDLINE, EMBASE, and Cochrane Database from inception through September 2022. The inclusion criteria were the studies that reported vaptans' safety or efficacy outcomes compared to placebo or standard therapies. The study protocol was registered with the International Prospective Register of Systematic Reviews (PROSPERO; CRD 42022357307). Five studies were identified, comprising three RCTs and two cohort studies, enrolling a total of 1840 participants. Regarding short-term efficacy on days 4-5, vaptans exhibited a significant increase in serum sodium concentration from the baseline in comparison to the control group, with a weighted mean difference of 4.77 mmol/L (95% CI, 3.57, 5.96; I2 = 34%). In terms of safety outcomes, the pooled incidence rates of overcorrection were 13.1% (95% CI 4.3, 33.6; I2 = 92%) in the vaptans group and 3.3% (95% CI 1.6, 6.6; I2 = 27%) in the control group. Despite the higher correction rate linked to vaptans, with an OR of 5.72 (95% CI 3.38, 9.70; I2 = 0%), no cases of osmotic demyelination syndrome were observed. Our meta-analysis comprehensively summarizes the efficacy and effect size of vaptans in managing SIADH. While vaptans effectively raise the serum sodium concentration compared to placebo/fluid restriction, clinicians should exercise caution regarding the potential for overcorrection.

Pseudo-pheochromocytoma due to obstructive sleep apnea: a case report

SUMMARY

Obstructive sleep apnea (OSA) is a condition of intermittent nocturnal upper airway obstruction. OSA increases sympathetic drive which may result in clinical and biochemical features suggestive of pheochromocytoma. We present the case of a 65-year-old male with a 2.9-cm left adrenal incidentaloma on CT, hypertension, symptoms of headache, anxiety and diaphoresis, and persistently elevated 24-h urine norepinephrine (initially 818 nmol/day (89-470)) and normetanephrine (initially 11.2 µmol/day (0.6-2.7)). He was started on prazosin and underwent left adrenalectomy. Pathology revealed an adrenal corticoadenoma with no evidence of pheochromocytoma. Over the next 2 years, urine norepinephrine and normetanephrine remained significantly elevated with no MIBG avid disease. Years later, he was diagnosed with severe OSA and treated with continuous positive airway pressure. Urine testing done once OSA was well controlled revealed complete normalization of urine norepinephrine and normetanephrine with substantial symptom improvement. It was concluded that the patient never had a pheochromocytoma but rather an adrenal adenoma with biochemistry and symptoms suggestive of pheochromocytoma due to untreated severe OSA. Pseudo-pheochromocytoma is a rare presentation of OSA and should be considered on the differential of elevated urine catecholamines and metanephrines in the right clinical setting.

LEARNING POINTS

Obstructive sleep apnea (OSA) is a common condition among adults. OSA may rarely present as pseudo-pheochromocytoma with symptoms of pallor, palpitations, perspiration, headache, or anxiety. OSA should be considered on the differential of elevated urine catecholamines and metanephrines, especially in patients with negative metaiodobenzylguanidine (MIBG) scan results.

Vasopressin V2-receptor antagonists in patients with cirrhosis, ascites and hyponatremia

Hyponatremia is a common problem in patients with advanced cirrhosis. It develops slowly (paralleling the rate of progression of the liver disease) and usually produces no neurological symptoms, although it may exacerbate hepatic encephalopathy. For patients awaiting liver transplantation a low serum sodium level is a strong predictor of pretransplant mortality, independent of the Model for End-stage Liver Disease score (MELD). The pathogenesis of hyponatremia is related to the hemodynamic changes and secondary neurohormonal adaptations that occur in patients with cirrhosis and ascites. The nonosmotic release of arginine vasopressin is the principle cause of the hyponatremia and vasopressin-receptor antagonists are a new class of drugs recently approved for treatment of cirrhotic hyponatremia. In this article we review the safety and efficacy of V2-receptor antagonists in patients with cirrhosis, ascites and hyponatremia.

Short-term efficacy and safety of vasopressin receptor antagonists for treatment of hyponatremia

BACKGROUND

We performed a meta-analysis to systematically measure efficacy and safety of vasopressin receptor antagonists (VRAs) tested in randomized controlled trials for treatment of hyponatremia.

METHODS

MEDLINE, ClinicalTrials.gov, and scientific abstracts were searched without language restriction. Two authors independently screened citations and extracted data on patient characteristics, quality of reports, and efficacy and safety endpoints.

RESULTS

Eleven trials were identified (1094 patients). By meta-analysis, VRAs achieved a net increase in serum sodium concentration ([Na(+)](serum)) relative to placebo of 3.3 mEq/L at day 1 (95% confidence interval [CI], 2.7-3.8), and 4.2 mEq/L at day 2 (95% CI, 3.6-4.8), persisting at days 3-5. Larger net increases in [Na(+)](serum) at days 1-4 were observed in euvolemic hyponatremia and with higher doses. VRAs induced a net increase in effective water clearance relative to placebo of 1244 mL at day 1 (95% CI, 920-1567), persisting at days 2 and 4. VRAs were associated with odds ratios of 3.0 for overly rapid correction of [Na(+)](serum) (P <.001), 7.8 for development of hypernatremia (P <.001), 3.3 for thirst development (P <.001), and 2.2 for postural hypotension (P=.04).

CONCLUSIONS

Short-term use of VRAs in treating hyponatremia was successful at raising [Na(+)](serum). Additional experience is required to guide their optimal use and minimize safety concerns.