Hyponatremia is a common clinical condition encountered in the hospital setting. Syndrome of inappropriate antidiuretic hormone (SIADH) is an important and one of the most common causes of hyponatremia. SIADH accounts for approximately one-third of all cases of hyponatremia. Tolvaptan is a vasopressin receptor antagonist used to treat SIADH. Hepatoxicity is a rare yet dangerous side effect from Tolvaptan use. We present a case of cholestatic liver injury in an elderly female who presented with hyponatremia. She received two doses of tolvaptan 15mg and developed worsening in her total bilirubin (T Bili) and alkaline phosphatase (Alk Phos) levels. Tolvaptan is known to cause elevated transaminase levels and the mechanism of action is thought to be idiosyncratic. Fortunately, the patient responded with an improvement in T Bili and Alk Phos levels after stopping tolvaptan. This case highlights the cautious use of tolvaptan in elderly patients with SIADH as even small doses can potentiate hepatotoxicity.
Keywords: drug-induced hepatotoxicity; hyponatremia; siadh; tolvaptan.