A case series of suicides by sodium azide ingestion

Abstract

To investigate the involvement of sodium azide in 13 forensic apparent suicides. Cases with suspicion of an intentional sodium azide ingestion confirmed by blood analysis were included. All blood samples were collected at the scene by the forensic physician. In six cases, the blood was femoral blood, in the other cases the origin was unknown. Nine blood samples were preserved with sodium fluoride and heparin or oxalate as anticoagulant, four contained EDTA as anticoagulant. The cases were screened for the presence of alcohol, drugs of abuse and medicines in blood. Azide in blood was identified and quantified after derivatization with pentafluorobenzylbromide (PFBBr) using GC-MS. In some cases other biological matrices were available for analysis as well. Thirteen cases were included (male/female: 2/11; age range: 27–86 years). Most bodies were found in their homes. Two victims were found in the garden needing resuscitation and eventually died in the hospital. In almost all 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. In three cases, a forensic autopsy was performed and the pathologist found no anatomical cause of death. Toxicological analysis for the presence of alcohol, drugs of abuse and medicines resulted in no indications for a toxicological cause of death. In all cases, medicines were found, especially analgesics, opioids and anti-emetics. Alcohol was detected in three cases. The median azide blood concentration was 17 mg/L (interquartile range: 13.5–20.5 mg/L). Azide was measured in other biological matrices in four cases showing higher azide concentrations in vitreous humor and lower azide concentrations in heart blood and urine compared to the blood obtained by the forensic physician. Median concentrations in vitreous humor, heart blood and urine were 26, 8 and 7 mg/L, respectively. In 11 cases, very high concentrations of azide were found in the blood (13 to 26 mg/L), corresponding with concentrations that were measured in persons who died after apparent intentional ingestion of sodium azide. In two cases, no toxicologically relevant results were found, except for azide. However, the measured azide concentrations were lower (about 1 mg/L), possibly due to degradation as a consequence of prolonged unsuitable storage prior to arrival at the institute. Unfortunately, no other biological matrices were available. These victims were found together and a container with label of sodium azide was found near them. The mentioned dose on the label of 3 gram is higher than earlier reported lethal doses of 700 mg. Higher azide concentrations in vitreous humor suggest good permeation and postmortem stability. It was concluded that the high concentration of azide can explain the death in 11 of our cases. In 2 cases, death by an azide overdose cannot be concluded but also cannot be excluded. Although femoral blood is the specimen of choice, vitreous humor is a good alternative when suspecting an azide overdose.