Suicide kit purchased on the Internet: A case report of self-poisoning with pentobarbital

Abstract

Popularization of assisted-suicide and increase of online drug sellers could lead to resurgence of self-poisoning by a forgotten drug: pentobarbital. We report a case of self-poisoning with pentobarbital purchased on a Chinese website. A 43-year old woman with a background history of borderline personality disorder ingested at home a “suicide kit” (pentobarbital sodium) purchased beforehand on the Internet, a few minutes before calling the French national emergency telephone number. Upon admission, she was comatose, Glasgow Coma Score (GCS) 3/15, symmetrical slight myosis, generalized hypotonia and hyporeflexia. Blood pressure was 96/66 mmHg, heart rate was 93/min, and body temperature was 33.3 °C. Blood gas analysis showed a metabolic acidosis and severe hypoxemia, related to an aspiration pneumonia (arterial pH 7.30, pCO 2 40.7 mmHg, pO 2 63.3 mmHg with F i O 2 = 1). Hemodynamic instability rapidly appeared and norepinephrine infusion was started (up to 0.32 μg/kg/min). At day 2, clinical examination revealed signs consistent with brain death, i.e. bilateral mydriasis with absence of pupillary and oculo-cardiac reflexes. Electroencephalographic study found a severe diffuse slowing compatible with a sedative state. Plasma pentobarbital concentration was 19.9 μg/mL. At day 3, brain-stem reflexes reappeared, although pentobarbital concentration was still beyond lethal range, at 18.1 μg/mL. Neurological evolution was then progressively favourable. GCS was 5/15 at day 5, corresponding to a concentration of 9.4 μg/mL, and 15/15 at day 6 allowing extubation of the patient. She was finally discharged to the psychiatry department at day 10. Pentobarbital is a short-acting barbiturate, now rarely used in suicide attempt because it is no longer prescribed for medical purposes in most countries. Only a few cases have been published in the last decade, mostly among veterinarians because this drug is used as euthanasia agent. Pentobarbital is indeed the drug of choice for assisted-suicide. Pentobarbital is a weak acid with high lipid-solubility. After oral absorption, it is readily absorbed with an onset of action of 10 to 60 minutes. The degree of protein binding is about 45 to 70% and the volume of distribution is 0.5 to 1L/Kg. The plasma half-life for pentobarbital is 15 to 50 hours and appears to be dose-dependent. Renal excretion is negligible (< 1%). Pentobarbital is metabolized by the liver and excreted in the urine as inactive metabolites. Consciousness impairment, respiratory and circulatory depression are the main effects of acute poisoning. At worst, severe poisoning can mimic clinical and EEG features of brain death. Therapeutic blood levels are 1–3 μg/mL; levels are considered toxic at 5 μg/mL or more and reported lethal blood concentrations range from 10 to 169 μg/mL. Management of pentobarbital poisoning is mainly based on supportive care. Invasive mechanical ventilation, fluid loading and vasopressors are required in most severe cases. Several procedures to enhance elimination have been reported. Forced diuresis with urinary alkalinisation is not effective for short-acting barbiturates. Hemodialysis, hemoperfusion or continuous venovenous hemodiafiltration have been proposed as therapeutic options but improvement in supportive therapies make these techniques obsolete. Pentobarbital is readily available without prescription on the Internet. Although there is little public awareness about this drug, current mediatisation of assisted-suicide could lead to an increased interest from suicide attempters. Supportive care is the cornerstone of medical management.