# Case Report of Acute Severe Hyponatremia Induced by Desmopressin Administration During Chemotherapy

## TL;DR

A 70-year-old man developed severe low sodium levels after resuming a medication called desmopressin during chemotherapy, highlighting the need to carefully manage this drug during cancer treatment.

## Contribution

This case highlights the risk of desmopressin-induced hyponatremia during chemotherapy and advocates for its discontinuation to ensure treatment safety.

## Key findings

- Resuming desmopressin during chemotherapy led to CTCAE Grade 4 hyponatremia.
- Discontinuing desmopressin prevented recurrence of hyponatremia in subsequent chemotherapy cycles.
- The patient completed all planned chemotherapy cycles after desmopressin was stopped.

## Abstract

Patients undergoing chemotherapy are prone to developing hyponatremia due to insufficient oral intake because of nausea and vomiting, administration of large volumes of intravenous fluids, syndrome of inappropriate antidiuretic hormone secretion induced by chemotherapeutic agents, adrenal insufficiency, and drug interactions. Severe hyponatremia during chemotherapy interferes with continuation of cancer treatment. In addition, it may be difficult to distinguish hyponatremia from chemotherapy‐related adverse effects because of symptom similarity. This report presented a case of desmopressin‐induced severe hyponatremia during chemotherapy and discussed the appropriateness of discontinuing desmopressin administration. A 70‐year‐old male was hospitalized for postoperative adjuvant chemotherapy with cisplatin and vinorelbine for a pathological stage IIB adenocarcinoma of the right lower lung lobes. The patient had been taking oral desmopressin (25 μg daily) for 4 years to treat nocturnal polyuria. Desmopressin was discontinued on day 1 of chemotherapy because of a contraindicated combination with dexamethasone, which was administered as an antiemetic. Desmopressin was resumed on day 6, but was followed by Common Terminology Criteria for Adverse Events (CTCAE) Grade 3 nausea, anorexia, and CTCAE Grade 4 hyponatremia (serum sodium concentration of 119 mEq/L) on day 7. Severe hyponatremia progressed following the resumption of desmopressin treatment. Desmopressin was not reintroduced thereafter, and subsequent chemotherapy cycles were continued without recurrence of hyponatremia. The patient completed all four planned adjuvant chemotherapy cycles. This case study highlighted the importance of carefully evaluating the necessity of continuing desmopressin administration and considering its discontinuation during chemotherapy to prevent the onset of hyponatremia.

Resuming desmopressin during chemotherapy can precipitate severe hyponatremia; its necessity should be reassessed and discontinuation considered to ensure safe continuation of cancer treatment.