Can Lexapro Cause Diabetes Insipidus?
No, Lexapro (escitalopram) does not cause diabetes insipidus (DI), but it can cause the opposite condition—SIADH (syndrome of inappropriate antidiuretic hormone secretion)—which results in hyponatremia, not the hypernatremia and dilute urine seen in DI. 1
Understanding the Distinction
Diabetes insipidus and SIADH are opposite disorders of water balance:
- Diabetes insipidus is characterized by polyuria (excessive urination), polydipsia (excessive thirst), dilute urine (osmolality <200 mOsm/kg), and high-normal or elevated serum sodium 2
- SIADH presents with hyponatremia, low serum osmolality, and inappropriately concentrated urine—the exact opposite of DI 2
What Lexapro Actually Causes
Escitalopram, like other SSRIs, is associated with SIADH, not diabetes insipidus. 1 A documented case report describes a patient who developed SIADH after 4 weeks of escitalopram treatment, with hyponatremia improving after drug discontinuation 1. While this is an uncommon side effect, clinicians should monitor high-risk patients (elderly, those on diuretics, those with baseline hyponatremia) for development of SIADH when prescribing escitalopram 1.
Drugs That Actually Cause Diabetes Insipidus
The medications most commonly associated with drug-induced DI are:
- Lithium salts (most common cause, affecting ~10% of patients on long-term therapy) 3
- Foscarnet (second most common in WHO adverse effect database) 3
- Clozapine (third most common) 3
- Other culprits include antimicrobials and cytostatics in critically ill patients 3
Drug-induced DI is always nephrogenic (kidney unresponsiveness to ADH), not central 3. This is diagnosed by demonstrating renal unresponsiveness during a water deprivation test or after desmopressin administration 3.
Clinical Pitfall to Avoid
Do not confuse the polyuria/polydipsia from uncontrolled diabetes mellitus with diabetes insipidus. 2 Diabetes mellitus causes polyuria through osmotic diuresis from glucosuria and is characterized by elevated blood glucose (≥126 mg/dL fasting or ≥200 mg/dL random with symptoms), whereas DI shows normal glucose with inappropriately dilute urine and elevated serum sodium 2.
If a patient on escitalopram develops confusion, lethargy, or seizures, check serum sodium immediately—you're looking for hyponatremia from SIADH, not hypernatremia from DI 1.