Pharmacokinetics of insulin disappearance after massive overdosing

Influence of Preservatives on Insulin in Postmortem Blood: Application to a Case of Insulin Aspart Suicide

Insulin aspart (NovoRapid®, NovoMix®, Novolog® and Fiasp®) is a fast-acting analog of human insulin, indicated in the treatment of type I and II diabetes. It is administered before meals to mimic the physiological insulin secretion that follows a rise in blood glucose. Its misuse for the purposes of suicide and murder and in the context of factitious order has often been described. In forensic medicine, the identification of insulin in biological samples has always been complex. In this paper, we present a case of suicide of a 64-year-old man who died after the injection of insulin aspart. He was suffering from terminal lung cancer and left a letter explaining the reasons for his suicide. Four empty NovoRapid® pens were found near the body. Body examination was unremarkable, and the femoral blood was collected in two dry Vacutainer™ tubes (red cap) and two sodium fluoride (NaF) tubes (gray cap). A liquid chromatography coupled to high-resolution mass spectrometry method was used to identify and discriminate insulin aspart from human insulin after immunopurification in the blood samples and in the pens. Blood specimens tested positive for insulin aspart with the concentrations of 36 and 37 ng/mL in dry tubes and 58 and 71 ng/mL in tubes containing NaF when tested ∼3 weeks after the collection of the specimens. The contents of the pens also matched with insulin aspart. The stability of insulin in blood is a critical point in the interpretation of the concentrations due to their rapid decrease caused by the activity of proteases in blood. During a degradation study implemented to compare three preservatives and dry tubes, suitable insulin aspart stability was observed with disodium salt of ethylenediaminetetracetic acid and NaF. Given that NaF is standard in forensic toxicology for measuring blood alcohol concentrations, the authors suggest its use for blood collection when insulin intoxication is suspected.

Attempted Murder of a Young Child Followed by an Attempted Suicide of the Mother by Injection of Insulin Aspart: Identification of Quantification of Insulin by LC-HRMS and UPLC-MS/MS in Blood of the Two Cases

The identification and quantification of insulin and its analogues have always been a challenge in the forensic field. Murder, suicide attempts and induced hypoglycemia in the context of factitious disorders have been described with the use of synthetic analogues of human insulin. There is very few information in the literature about aspart insulin concentrations in overdose cases. In this paper, we present a case of a nurse who tried to murder her 10-year-old daughter by injecting her aspart insulin and who, later, tried to commit suicide by injecting herself the same hormone. Two empty syringes and a FIASP ® Flextouch pen were found in the woman's apartment. A LC-HRMS method was developed in order to identify and discriminate aspart insulin from human insulin in blood samples as well as in syringes and pen, while an LC-MS/MS method was developed for the quantification of insulin in blood samples. Aspart insulin tested positive at 5.7 and 2.4 ng/mL in the blood specimens of the mother and the child, respectively. The contents of the syringes and pen also corresponded to aspart insulin. Although the mother claims to have injected an overdose of aspart insulin, the concentrations found were in the therapeutic range for subjects under therapy. Due to the high instability of insulin and the long time elapsed between sampling and forensic analysis (8 months) due to administrative reasons, the concentration at the time of collection was probably much higher. In this case, it was possible to identify aspart insulin and discriminate it from human insulin in a context of attempted murder and subsequent attempted suicide using high-resolution mass spectrometry, which is of paramount importance in forensic medicine.