SIADH with Severe Hyponatremia in an Elderly Man with Herpes Zoster Infection: A Causal or Casual Association?

Diagnostic assistance provided by a pharmacist for the syndrome of inappropriate antidiuretic hormone secretion caused by carboplatin plus nab-paclitaxel chemotherapy in an elderly patient with lung cancer: a case report

BACKGROUND

Syndrome of inappropriate antidiuretic hormone secretion (SIADH) is the most common cause of hyponatremia. Although SIADH induced by carboplatin (CBDCA) plus nab-paclitaxel (nab-PTX) has been reported, there is limited evidence for SIADH being suspected by pharmacists during chemotherapy in elderly patients and contributing to early intervention through diagnostic support for physicians.

CASE PRESENTATION

An 84-year-old man was diagnosed with stage 3A squamous cell carcinoma of the right lung. Genetic mutations and expression of programmed cell death protein ligand 1 were < 1%. The patient was started on CBDCA area under the curve of 5 mg/mL·min on day 1 plus nab-PTX 70 mg/m2 on days 1, 8 and 15 once every 3 weeks. The serum sodium level immediately before the start of chemotherapy was 141 mmol/L. On day 8, it decreased to 119 mmol/L, and the physician started oral sodium chloride (3 g/day) administration. Because the pharmacist suspected that this hyponatremia may be due to chemotherapy-induced SIADH, the pharmacist suggested an examination of plasma and urine osmolality and urinary sodium levels to the physician. The serum creatinine level, plasma osmolality, urine osmolality, and urinary sodium level were 1.06 mg/dL, 253 mOsm/kg, 355 mOsm/kg, and 59 mEq/L, respectively; furthermore, the patient was not dehydrated. Based on the findings, a diagnosis of chemotherapy-induced SIADH was made. The physician and pharmacist conferred and decided to continue chemotherapy with frequent monitoring of serum sodium levels. Subsequently, the serum sodium level improved to 139 mmol/L on day 20 without additional treatment, and oral administration of sodium chloride was discontinued on day 22. The patient completed five cycles of chemotherapy. Computed tomography revealed a partial response throughout chemotherapy. Furthermore, sodium levels did not decrease again throughout chemotherapy. The Naranjo Adverse Drug Reaction Probability Scale score was 5 points, which is categorized as "probable."

CONCLUSIONS

We encountered a case in which the patient developed chemotherapy-induced SIADH but was able to continue chemotherapy because of early pharmacist intervention. In elderly patients without genetic mutations and few treatment options, even if they develop SIADH, chemotherapy should be continued with monitoring of serum sodium levels by physicians and pharmacists.

Cutaneous Herpes Zoster Infection as a Rare Etiology of Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH): A Case Report

Herpes zoster is caused by a reactivation of the varicella-zoster virus after primary manifestation during childhood as chicken pox, commonly occurring in elderly and immunosuppressed patients. Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH) is defined by the unsuppressed release of antidiuretic hormone (ADH) from the pituitary gland, with impaired water excretion causing hyponatremia. Though limited, literature supports herpes zoster infection inducing SIADH, through a proposed mechanism of alteration of the ADH regulator pathway due to viral infection of the dorsal root ganglion (DRG). Our case is distinct in that our patient presented elements of hypovolemic hyponatremia with concomitant SIADH.

Syndrome of Inappropriate Secretion of Antidiuretic Hormone Associated With Varicella Infection in Children

A 9-year-old girl with remarkable hyponatremia was diagnosed with SIADH that was likely secondary to varicella. Under appropriate treatment, her serum sodium returned to the normal level. There was no evidence of hyponatremia at a 3-month follow-up. We propose that medical professionals need to consider the existence of that SIADH when treating patients with varicella who present with severe hyponatremia.

Duloxetine and Angiotensin II Receptor Blocker Combination Potentially Induce Severe Hyponatremia in an Elderly Woman

We encountered a case of syndrome of inappropriate antidiuretic hormone secretion (SIADH) caused by duloxetine, serotonin and norepinephrine reuptake inhibitor (SNRI). A 74-year-old woman complaining of severe lethargy was transferred to our emergency department. Her serum sodium level was 109 mEq/L. Plasma hypo-osmolality with urine normo-osmolality was observed, indicating SIADH. Her essential hypertension had long been treated with telmisartan, and she had just started duloxetine 20 mg/day for chronic musculoskeletal pain 4 days prior to admission. On prescribing duloxetine in the primary care setting, clinicians should be aware of the possibility of duloxetine-induced hyponatremia, particularly in combination with telmisartan.