Wed3November0919PM 13

A 62-year-old female is referred with mild confusion.

She has a history of depression, type 2 diabetes mellitus and angina for which she takes a variety of medications.

Investigations reveal:

Sodium concentration 123 mmol/L (137-144)

Potassium 3.4 mmol/L (3.5-4.9)

Urea 5.2 mmol/L (2.5-7.5)

Creatinine 70 µmol/L (60-110)

Plasma osmolality 260 mosmol/L

Urine osmolality 650 mosmol/L

Urine sodium concentration 38 mmol/L

What agent may be responsible for her presentation?

(Please select 1 option)

Lisinopril

Fluoxetine This is the correct answer

Metformin

Lithium Incorrect answer selected

Pioglitazone

Explanation

This patient has syndrome of inappropriate antidiuretic hormone (SIADH) as suggested by the hyponatraemia with high urine sodium and osmolality.

Drugs that may cause SIADH include:

Selective serotonin reuptake inhibitors (SSRIs) (fluoxetine)

Tricyclic antidepressants

Sulphonylureas

Thiazides, and

Carbamazepine.

Other causes of SIADH include:

Pneumonias

Meningitis Guillain-Barré

Trauma, and

Malignancy.

Lithium would cause diabetes insipidus (DI).

Answer Statistics

1

7%

2

50%

3

37%

4

8%

Times answered: 283