Endocrine Abstracts

Introduction: Current treatment for SIADH related hyponatremia is unsatisfactory. We describe two cases of effective Tolvaptan use in SIADH related to disseminated cancer.

Case 1: Fifty-three year old female with metastatic ovarian carcinoma, vomiting from partial intestinal obstruction, was referred with sodium 121 mmol and normal renal function. She was clinically dry and mildly confused. SIADH was confirmed but urine Na was <10 suggestive of hypovolemia.

IV fluid was commenced followed by Demeclocycline – latter caused renal failure and was stopped. Cyclizine pump was started and soon she was able to drink more and renal function normalised. Tolvaptan 15 mg was started (sodium 122 mmol) when adequately hydrated and Urine sodium >20. Within 48 h sodium was 127 mmol and 135 mmol/l five days after starting Tolvaptan. Family wanted her home as she was now relatively alert and stable. Unfortunately she passed away 3 days later.

Case 2: Fifty year old lady with ovarian cancer and abdominal metastases – was referred with falling Sodium levels – 138 in April, 134 June, 126 in July (admission). Investigations confirmed SIADH. Fluid restriction was poorly followed and Sodium only improved to 128 mmol/l. Started 15 mg of Tolvaptan. Clinically felt better with progressive rise in Sodium over a week – 134, 139, 140, 142 mmol/l. Tolvaptan was stopped and she was discharged to a Hospice. Day 7 post-discharge sodium was 133 and day 14 it was 134 mmol/l.

Discussion: Tolvaptan (new Vasopressin receptor antagonist) has shown promise in treating hyponatremia due to SIADH. Intermittent vomiting in the 1st patient meant that fluid restriction long-term was impractical and ineffective in the 2nd patient. Demeclocycline caused renal toxicity. Tolvaptan raised and maintained sodium levels without compromising safety, enabled removal of fluid restriction and allowed the patient to spend the last few days at home. It is important to correct dehydration before using Tolvaptan.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.