Suicide by sodium nitrite ingestion: a systematic review

Sodium nitrite (NaNO₂) is an odorless inorganic compound appearing as a yellowish to white powder, primarily used as a food additive. An alarming increasing trend in suicides involving NaNO₂ ingestion has been recently observed. The aim of this study is to present a systematic review of intentional NaNO₂ poisonings, focusing on the epidemiological characteristics of the victims, their psychiatric history, the setting and circumstances of death, as well as autopsy, histological and toxicological results. A total of 24 papers satisfied the inclusion criteria reporting 94 suicides by NaNO₂ ingestion. Most victims were male (62.8%), belonging to the 13-40-year-old age group. Psychiatric history was available in 43 cases, with depression being the most reported disorder (19 cases). Autopsy and/or external examination were performed in 63 cases, mostly showing unspecific signs of asphyxia and dark discoloration of the hypostasis and blood. Methemoglobin (Met-Hb) levels in blood were available in 49 suicides, ranging from 6 to 92%. In 35 cases levels exceeded 30%, with 19 victims showing concentrations above 50%. Nitrites (NO₂) and nitrates (NO₃) were analyzed from different biological samples including blood, urine, gastric content, and other tissues. NO₂ were detected in 44 cases, while NO₃ in 30 victims. Blood was the most analyzed matrix with NO₂ and NO₃ concentrations ranging from 0.03 µg/mL to 372.65 µg/mL and from 0.899 µg/mL to 1,597.9 µg/mL, respectively. In addition, a case of fatal self-poisoning by oral ingestion of NaNO₂, which came to the author's attention, is presented.