USMLE (United States Medical Licensing Examination) Step 1 Practice Exam

Which of the following drugs is a known cause of Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH)?

1. Carbamazepine

2. Cyclophosphamide

3. SSRI

4. All of the above

The correct answer is: All of the above

Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH) is a condition characterized by excessive release of antidiuretic hormone (ADH), which leads to water retention, dilutional hyponatremia, and concentrated urine. Various medications can induce SIADH, and all of the mentioned drugs are known to cause this condition. Carbamazepine, an anticonvulsant, has been recognized for its potential to stimulate the release of ADH, contributing to SIADH development, particularly in certain populations or with higher doses. Cyclophosphamide, a chemotherapy agent, can also lead to SIADH. Its effects on the kidneys can result in enhanced sensitivity to ADH or increased release of the hormone, thus promoting water retention. Selective serotonin reuptake inhibitors (SSRIs) are another class of drugs associated with SIADH. They can increase serotonin levels, which may enhance ADH secretion. Since all the options listed are recognized causes of SIADH, the choice indicating that all of them contribute to the syndrome is accurate.