Researchers are urging greater awareness among medical professionals and policy-makers regarding the misuse of sodium nitrite as cases of poisoning involving the substance are increasing, not just around the globe but also in South Africa.
In the SA Medical Journal, pathology experts Varushka Bachan and Marie Belle Hlela unpack a case series examining three fatalities involving the substance – suspected suicides – investigated at the Observatory Forensic Pathology Institute (formerly Salt River Mortuary) in Cape Town between 2020 and 2023.
Sodium nitrite (NaNO2) ingestion results in methaemoglobinaemia, which can cause hypoxia, metabolic acidosis and death. It is an inorganic salt, easily accessible and widely used as a colourant, food preservative and corrosion inhibitor.
The three cases all involved sodium nitrite, with labelled containers found at the death scenes. Post-mortem findings included chocolate-brown discolouration of the blood, blue-grey discolouration of the nail beds, and distinctive skin lividity.
Toxicological analyses included ethanol, common drugs of abuse, methaemoglobin and sodium nitrite determined in various matrices.
This report highlights the importance of thorough death scene investigations and challenges in ancillary testing, and contributes to the literature on sodium nitrite-related suicides. The accessibility and rapid lethality of the chemical underscore the need for heightened awareness related to its misuse.
The odourless, water-soluble and hygroscopic powder is also used in medicine as an antidote to cyanide poisoning, the therapeutic dose being 300 mg (10 mL) intravenously infused – while the lethal dose in humans is estimated to be between 1.0 g and 2.6 g in a typical adult.
Accessibility
Aside from its practical uses, sodium nitrite has gained attention as a method of suicide due to its accessibility, affordability and rapid lethality. Ingestion of toxic levels results in elevation of blood methaemoglobin (MetHb), leading to systemic hypoxia, metabolic acidosis, cyanosis and potential death.
While cases of sodium nitrite poisoning have been documented globally, they are under-reported in South Africa, where its use is regulated by the Foodstuff, Cosmetics, and Disinfectants Act, as amended.
This report highlights three suspected cases of suicide, in which we aim to expand the understanding of the medico-legal implications and toxicological challenges of such cases.
Case one
Cleaners found a 63-year-old man unresponsive on his hotel bathroom floor.
A month before, he had concluded funeral arrangements for himself. There were no apparent signs of injury, and no suicide note. A funeral policy card was displayed on the bathroom counter. Two plastic containers labelled ‘Sodium Nitrite, NaNO2’ were found in the room.
Autopsy revealed an obese adult male with a body mass index (BMI) of 37.3. No external injuries were noted. Conjunctival and facial congestion were present. Lividity was noted posteriorly, while the fingernails also displayed blue-grey discolouration at the tips.
Internal examination revealed a chocolate-brown discolouration of the blood and viscera. The organs were congested and myocardial and prostate hypertrophy and moderate atherosclerotic disease were present.
Histological examination of the heart revealed moderate coronary artery atherosclerosis and myocardial fibrosis. Grade 4 hepatic steatosis (>66%), hypertensive renal disease and moderate pulmonary oedema were observed. Post-mortem blood and urine samples were submitted for routine toxicological analysis, including blood alcohol and drug testing (panel of 29 common substances).
An additional request for MetHb analysis (blood and powder exhibit) was made. No ethanol (0.00 g/100 mL) or drugs were found. The MetHb level in the blood was 18.1% using an unvalidated carbon monoxide (CO)-oximetry method. An ultraviolet-visible spectrophotometric preliminary screen revealed sodium nitrite in the powder exhibit.
Case two
A 25-year-old female student was found unresponsive in her student residence. White foam-like froth was visible at the nose and mouth, with intense blue discolouration of the fingernails, indicating cyanosis. She showed no signs of injury.
Numerous containers of over-the-counter medications were beside her, including one labelled sodium nitrite. A letter of instructions was found, indicating where her suicide letter and belongings could be found. She had a history of depression and anxiety.
The autopsy revealed an obese female adult with a BMI of 37.3, with no significant external markings or injuries. There was notable intense blue discolouration of the fingernails, with dark brown discolouration of blood and viscera. No significant wounds or injuries were noted.
The organs were generally congested, with oedematous lungs and small bilateral pleural effusions. The liver was particularly noted to be chocolate-brown in colour. There was no significant natural disease present and no sign of pregnancy.
Postmortem biological samples found neither ethanol (0.00 g/100 mL) nor drugs present.
Case 3
Police found a 24-year-old male student unresponsive in a car at the beach – the previous day he had sent a concerning message to his girlfriend, and had a medical history of depression.
Numerous packages of medication were found, including anti-nausea pills and painkillers, and a bottle labelled sodium nitrite. Two plastic containers of clear liquid were also present. A delivery note in the vehicle indicated the purchase of sodium nitrite and its delivery the day before his body was discovered.
An autopsy revealed a muscular young male with a BMI of 30.9. Hypostasis was dark blue, purple and brown, with the distribution consistent with the position of his body in the driver’s seat. No injuries were noted. The organs and viscera revealed brown discolouration. The stomach contained dark-coloured fluid with a strong chemical odour, and no undissolved tablets were observed.
Post-mortem specimens, i.e, blood, bile, vitreous humor and gastric content, were submitted for analysis, including blood alcohol and drug testing (panel of 29 common substances). No ethanol (0.00 g/100 mL) was found, and the drug testing was positive for acetaminophen (13 mg/L) and codeine (0.033 mg/
Discussion
There has been an alarming rise in sodium nitrite-related suicides worldwide, particularly among young adults, driven by the easy accessibility of the substance and the dissemination of detailed instructions online. E-commerce platforms play a significant role in enabling access to sodium nitrite, often marketed as part of “suicide kits”.
These are frequently accompanied by advice on ingesting sodium nitrite in combination with alcohol or other drugs, like sedatives, anti-emetics and antacids, to minimise discomfort and enhance absorption, underscoring the need for regulatory intervention and public education.
Post-mortem findings are strikingly consistent. Key indicators include blue-grey lividity, chocolate-brown discolouration of the blood, intense cyanosis and pulmonary oedema.
In this report, sodium nitrite-labelled powder and/or containers were found at all three death scenes, corroborating patterns reported in the literature.
Furthermore, circumstantial evidence like internet searches, suicide notes and the victims’ medical histories, including prior suicide attempts, are invaluable for medico-legal investigations.
Two of our reported cases had a history of depression and the third had made plans for his death the previous month.
The identification of sodium nitrite as the toxic agent in poisoning cases can be challenging because of its non-specific presentation and the absence of obvious physical findings.
MetHb levels serve as a critical diagnostic marker, with elevated concentrations typically confirming poisoning. However, MetHb levels in fatal cases vary widely, complicating interpretations, especially after medical treatment (e.g, administration of the antidote methylene blue).
While MetHb levels >60% are generally considered “lethal”, lower concentrations have been reported, particularly in individuals with pre-existing comorbidities. Moreover, extended post-mortem intervals, inadequate storage conditions and poor sample quality (e.g, putrefied specimens) can significantly impact MetHb stability for CO-oximetric or spectrophotometric measurements, necessitating alternative testing strategies and leading to MetHb mis-estimations.
A reliable measurement of sodium nitrite levels in blood is challenging because of nitrites rapidly converting into nitrates, resulting in false low concentrations. Nitrite and nitrate determination in biological samples is indispensable for confirming sodium nitrite poisoning; however, its instability in blood, coupled with the scarcity of validated analytical methods for post-mortem matrices, poses significant hurdles.
Advanced techniques like spectrophotometry and chromatography require meticulous sample preparation, can be costly and time-consuming, and are prone to interference from endogenous substances.
Testing alternative matrices like vitreous humor, pericardial fluid and gastric contents can yield more reliable results.
Circumstantial evidence from death scenes, including the presence of sodium nitrite powder, drinking containers and suicide notes, plays a pivotal role in corroborating toxicological findings.
Investigations should routinely include alcohol, common drugs of abuse and medications, as substances like metoclopramide frequently co-occur in these cases.
Metoclopramide and similar drugs (e.g, ranitidine, ondansetron, olanzapine, famotidine, cimetidine), often part of ‘suicide kits’, are detected in multiple reports and can provide critical insights into the intent and circumstances of death. In our case 3, ondansetron, an anti-emetic, was present.
These cases underscore the importance of integrating scene evidence, toxicological data and circumstantial findings.
Without the scene and autopsy findings to guide the investigator in these cases, no conclusive cause of death could have been ascertained were the toxicological analyses solely relied upon.
This limitation could prove crucial where the scene may have been altered or if the victim has been moved and taken to hospital. Comprehensive death investigations, encompassing the simultaneous determination of MetHb, nitrite and nitrate levels in biological specimens, are critical.
Non-biological evidence, like sodium nitrite containers or related drugs and paraphernalia, also strengthens case conclusions. Despite the challenges, an interdisciplinary approach remains crucial in addressing these complex cases.
Sodium nitrite toxicity should be classified as a notifiable medical condition. Once reported, the source of sodium nitrite can be investigated and measures initiated to shut down the route of access.
Clinicians should consider nitrite toxicity in the differential diagnosis of cases with cyanosis and no apparent cardiovascular cause. Successful resuscitation after ingestion of 15 g of sodium nitrite has been reported, the patient initially presenting with loss of consciousness and cyanosis.
Treatment included supportive measures, as well as gastric lavage, activated charcoal and intravenous methylene blue.
Sodium nitrite-related suicides represent a growing public health concern globally and in SA.
The three cases presented highlight the chemical’s rapid lethality and the forensic challenges in its detection. Urgent action is required to address this emerging issue. Policymakers should enforce stricter regulations on the sale and distribution of sodium nitrite, particularly online.
Awareness campaigns targeting healthcare professionals, emergency responders and the public are crucial for early recognition and intervention. Furthermore, investment in toxicological research and the development of validated methods for detecting nitrite in biological samples are needed to improve diagnostic accuracy and support preventative measures.
V R Bachan,1,2 MB ChB, FC For Path (SA), MMed (For Path), Dip For Med (SA) Path;
M B K MHlela,1,3BSc, BSc (Med) Hons, MPhil, MPH
1 Division of Forensic Medicine and Toxicology, Department of Pathology, Faculty of Health Sciences, University of Cape Town
2 Observatory Forensic Pathology Institute, Forensic Pathology Service, Western Cape Department of Health and Wellness
3 Forensic Toxicology Unit, Forensic Pathology Service, Western Cape Department of Health and Wellness
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Risk factors for suicide over a lifetime — systematic review
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