To highlight a recent surge in new drug deaths resulting from sodium nitrite (NaNO2) toxicity in which the post mortem blood nitrite (NO2-) and nitrate (NO3) concentrations were measured. The University Hospitals of Leicester (UHL) NHS Trust post-mortem toxicology service receives samples from 27% of Her Majesty's Coroners in England and Wales, analysing approximately 4000 cases per year. We report a series of 15 cases, spanning an 18-month period, in which NaNO2 was the suspected cause of death. NaNO2 is an inorganic sodium salt that has several industrial applications, the most common being preserving meat products. Excess NaNO2 ingestion has also been associated with severe toxicity/death when consumed in excess either accidentally or intentionally. Recently, suicide kits containing NaNO2, and an anti-emetic drug, to assist with ingestion of NaNO2, have become available online. Excessive nitrite ingestion results in iron oxidation within haemoglobin and subsequent production and accumulation of methaemoglobin. Methaemoglobin cannot bind or transport oxygen effectively therefore severe tissue hypoxia and death result. Nitrite is also a vasodilator and can cause coronary ischaemia and stroke as a result of hypotension, tachycardia, and hypoxia.

Routine screening was performed on post mortem blood samples received as per usual laboratory protocol; including ethanol analysis by Headspace Gas Chromatography–Flame Ionisation Detection (HS GC-FID), drug screening by High Resolution Accurate Mass–Mass Spectrometry (HRAM-MS) and confirmatory drug quantitation by Liquid Chromatography–Tandem Mass Spectrometry (LC-MS/MS). In this series, the majority of case histories described the presence of NaNO2 at the scene of death/purchase of a suicide kit; therefore aliquots of post mortem blood were referred to a specialist laboratory (William Harvey Research Institute) for quantitative nitrite and nitrate analysis. Measurement was based upon the gas-phase chemiluminescent reaction between nitric oxide (NO) and ozone (O₃); NO levels were determined using an NOA 280A, Sievers NO analyser.

Fifteen post-mortem cases in which NaNO2 ingestion was considered the most probable cause of death were reported between January 2020 to July 2021; mean age 31 years (range 18 to 49), 8/15 (53%) male. In almost all cases the clinical history described mental health issues, depression, previous suicide attempts/overdose, self-harm or suicidal ideation. Two thirds of the cases listed prescribed anti-depressants/anti-psychotics; these drugs were detected in 6/15 cases. Ethanol was detected in 3/15 cases and anti-emetic drugs in 3/15 cases. Illicit drugs were present in two of the cases at concentrations suggestive of prior use. The mean nitrite and nitrate concentrations were 2106μmol/L (min–max 1.4–8100) and 7818μmol/L (14.5–21,100) respectively. Blood reference ranges for nitrite and nitrate are 0.1–0.4 and 20–40μmol/L respectively. Nitrite was elevated in all but one case, nitrate was elevated in 12/15 (80%) cases. For the majority of cases (9/15) individuals were discovered deceased; 4/15 cases emergency services attended and death occurred either on route to or following hospital admission. The remaining two cases gave insufficient detail regarding circumstances of death. One post mortem report described discolouration on post mortem consistent with the presence of methaemoglobinaemia.

The detection and quantitation of nitrite and nitrate during post-mortem toxicological investigations represents a significant challenge analytically and heavily relies upon circumstantial evidence. Even though it still remains a rare cause of death, it is worthwhile considering the possibility of sodium nitrite use in individuals with suicidal ideation given its apparent availability online. The provision of a quantitative nitrite/nitrate analytical service greatly assists in determining the cause of death in these cases.