Recurrent syndrome of inappropriate antidiuretic hormone secretion due to tolterodine in an elderly male patient.

Hyponatremia is defined as serum sodium of <135 mmol/L and equates with a low serum osmolality once translocational hyponatremia and pseudohyponatremia are ruled out. True hyponatremia develops when normal urine-diluting mechanisms are disturbed. In elderly patients, this complication is not uncommon, especially in nursing homes and assisted living facilities. Medications are often the most common cause of hyponatremia in these patients. Herewith, we reported a 65-year-old Saudi male, a known case of benign prostatic hypertrophy and hypertension, who developed recurrent hyponatremia secondary to tolterodine. To our knowledge, this is the fifth case reported in literature of such association.