Sodium azide is a chemical used as preservative for diagnostic reagents and propellant in automobile airbags. In the 1950s, it was investigated as a potential antihypertensive agent in low doses. Nowadays, it is easily available for online purchase. Azide is believed to cause its toxic effects through the inhibition of cytochrome oxidase resulting in cellular hypoxia. Toxic effects that may occur include hypotension, cardiac arrhythmia, respiratory depression, unconsciousness, coma and death.
As azide is currently not detected by routine screening, azide concentrations were determined in blood, vitreous humor and/or urine only in cases with suspicion of an intentional ingestion. Azide was identified and quantified after derivatization with pentafluorobenzylbromide and extraction with tetradecyldimethylammonium as liquid phase-transfer catalyst, using GC-MS and isotopically labeled azide as internal standard, based upon a procedure from Kage et al. [1] The cases were also screened for the presence of alcohol, drugs of abuse and medicines by routine techniques.
Twenty six cases were included (male/female: 9/17; age range 27-88 years). In 16 cases, a small container labeled with sodium azide was found at the scene and the total dose in the container, if classified, varied from 2 to 3 gram. Routine toxicological analysis resulted in no indications for a toxicological cause of death. In all cases, medicines were found, especially analgesics (21 cases), opioids (4 cases), anti-emetics (17 cases) and benzodiazepines (11 cases). Alcohol was detected in four cases. The median azide blood concentration was 16 mg/l (n=25, range 1-30 mg/l). Median concentrations in vitreous humor, heart blood and urine were 24 mg/l (n=5, range 9-29 mg/l), 7 mg/l (n=5 , range 0-16 mg/l) and 5 mg/l (n=5, range 2-11 mg/l), respectively.
It was concluded that the measured azide concentrations in blood could explain the death in 25 of our cases. In one case, the death was explained by the measured azide concentration in vitreous humor. Although femoral blood is the specimen of choice in forensic toxicology, the results of azide in vitreous humor show that it is a valuable additional matrix and it is advised to collect femoral blood and vitreous humor when suspecting an azide overdose.
Literature: [1] Determination of azide in blood and urine by gas chromatography - mass spectrometry. S. Kage et al., J. Anal. Toxicol. 2000, 24, 429-432.