Recurrent Hyponatremia: Levetiracetam - An Uncommon Cause.

Abstract

Dear Editor, Hyponatremia can be an adverse drug reaction with the use of some of the anti-seizure medications (ASM). Carbamazepine and oxcarbazepine are the most common ASMs which induce hyponatremia. Rarely sodium valproate, eslicarbazepine, lamotrigine, levetiracetam, and gabapentin have also been reported to cause hyponatremia.[1] We report a case of Levetiracetam induced hyponatremia and review the English literature of similar cases. A 50-year-old male had traumatic brain injury in November 2015 and neuroimaging was normal. He was started on prophylactic levetiracetam at another facility. Since then, he had three admissions for hyponatremia: First admission was for acute symptomatic seizures due to hyponatremia, serum sodium of 118 mmol/L; second admission in February 2016 for dizziness, serum sodium 131 mmol/L; and third admission during April 2016 for drowsiness, serum sodium 108 mmol/L [Table 1]. During the latter two admissions, the work-up for hyponatremia was suggestive of syndrome of inappropriate antidiuretic hormone secretion (SIADH). During the first admission, patient was on levetiracetam 500 mg q12h and the dose was escalated to 1000 mg q12h at discharge. Patient was started on tolvaptan 15 mg q24h at discharge in the first admission (25.12.2015). During his subsequent admissions, workup for other causes of hyponatremia was negative. He was continued with tolvaptan intermittently. Review of the case records and drug chart suggested possible relation between hyponatremia and levetiracetam, a diagnosis of levetiracetam induced hyponatremia was considered and levetiracetam was discontinued. Since then, he had no further episode of hyponatremia. Patient was not started on any ASM as it is not our practice to use ASMs for primary prophylaxis in traumatic brain injury.Table 1: Admission profile of the patientIn this patient, diagnostic workup suggested that SIADH was the possible mechanism for hyponatremia. He had a mild closed traumatic brain injury and normal brain imaging. This clinical scenario is very unlikely to cause SIADH. Workup for other causes of hyponatremia was negative. When levetiracetam was discontinued patient had no further episodes of hyponatremia. On Naranjo Adverse Drug Reaction Probability Scale[2] this patient had a score of 7 suggesting levetiracetam being the “probable” culprit responsible for hyponatremia. Review of English literature revealed report of four patients with levetiracetam induced hyponatremia [Table 2]. In four patients, including the present case SIADH was the mechanism of hyponatremia. There are no specific clinical characteristics which are common among these 5 cases. In all the patients, hyponatremia was corrected after withdrawing levetiracetam. In patient “3” in addition to levetiracetam, hydrochlorothiazide would have added to the misery of hyponatremia.Table 2: Characteristics of the patientsIn conclusion this case illustrates that chronic hyponatremia in a patient with epilepsy on ASMs, one should check the ASM list to exclude the possible drug that can be associated with hyponatremia. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.