Endocrine Abstracts

Introduction: Hyponatraemia is common biochemical abnormality in hospitalised patients and is difficult to manage in some cases. Tolvaptan is presently licensed in the UK for the treatment of hyponatraemia secondary to SIADH. We present our experience of using Tolvaptan.

Cases: Patient 1 was admitted with sagittal sinus thrombosis. Over 9 days serum sodium dropped from normal to 121 mmol/l with biochemical evidence of SIADH. The patient was treated with Tolvaptan for 4 days, after management with fluid restriction and Demeclocycline had failed. Sodium increased to 133 mmol/l and remained stable. Patient 2, an 83-year-old woman with background problems including atrial fibrillation, was admitted electively for pacemaker insertion. Serum sodium on admission was 129 mmol/l. Following pacemaker insertion, she developed heart failure and needed diuretics, which were difficult to continue as she developed significant hyponatraemia. Her nadir sodium level was 114 mmol/l, leading to neurological sequelae. She was prescribed Tolvaptan for 8 days, which improved her sodium. Over the next few months her sodium levels have remained stable. Patient 3 was admitted with fractured neck of femur and operated. Sodium on admission was normal, but dropped to 110 mmol/l by the 15th day. She became confused and biochemically had SIADH. She was initially managed with strict fluid restriction but this failed to improve matters. She was given Tolvaptan for 10 days. Hyponatraemia resolved rapidly and sodium levels remained normal since.

Discussion: Hospitalised patients can develop hyponatraemia due to a variety of causes and some can be very symptomatic. Tolvaptan use has been studied in multiple experimental and clinical trials which have used Tolvaptan for over 30 days. In clinical practice Tolvaptan appears to restore salt and water homeostasis rapidly following short-term use. Once the cause of hyponatraemia is treated normal sodium levels are maintained long-term.