[Hyponatremia associated with SSRI/NRSI: Descriptive and comparative epidemiological study of the incidence rates of the notified cases from the data of the French National Pharmacovigilance Database and the French National Health Insurance].

INTRODUCTION: Selective Serotonin Reuptake Inhibitors (SSRIs) and Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs) are frequently prescribed. These antidepressants can potentially induce serious hyponatremia through the SIADH syndrome. That seems to concern all molecules of these classes but the individual risk of each molecule is not well known. The aims of the study were to compare the incidence rate of each molecule in order to identify the existence of molecules more at risk of inducing hyponatremia and to characterize a profile of patients at risk for hyponatremia during a treatment with a SSRI or a SNRI.

METHOD: The cases of hyponatremia under SSRI/SNRI were extracted from the French pharmacovigilance database (BPNV). The exposition to the different SSRIs/SNRIs in the French population was estimated from the French National Health Insurance database (SNIIRAM) using a sampled database (Echantillon Généralistes des Bénéficiaires). The study ran from 01/01/2011 to 31/12/2013. The primary study endpoint was the incidence rate of notifications of the hyponatremia cases in patients treated by SSRI/SNRI and recorded into the BNPV database, related to the average annual number of corresponding treatments initiated during the same period.

RESULTS: The number of cases of hyponatremia included in the study was 169 for 3 749 800 adult patients initiating treatment. The incidence rate of cases was 1.64 for 100 000 persons per year (PY). The standardized incidence rates between the different molecules showed no difference except for duloxetine (2.79/100 000 PY p > 0.03). Identified risk factors were age, with a large increase of incidence rate from 75 years old (incidence 12.5 higher) and female gender.

CONCLUSIONS: Comparison of the incidence rates from spontaneous reports indicates a greater risk of hyponatremia for duloxetine for 2011-2013. This result needs to be confirmed by other studies. The advanced age and female sex are risk factors, irrespective of the molecule.