Evaluation of a fatal propofol intoxication due to self administration

Propofol exerts anti-anhedonia effects via inhibiting the dopamine transporter

Lasker's award-winning drug propofol is widely used in general anesthesia. The recreational use of propofol is reported to produce a well-rested feeling and euphoric state; yet, the neural mechanisms underlying such pleasant effects remain unelucidated. Here, we report that propofol actively and directly binds to the dopamine transporter (DAT), but not the serotonin transporter (SERT), which contributes to the rapid relief of anhedonia. Then, we predict the binding mode of propofol by molecular docking and mutation of critical binding residues on the DAT. Fiber photometry recording on awake freely moving mice and [¹⁸F] FP-CIT-PET scanning further establishes that propofol administration evokes rapid and lasting dopamine accumulation in nucleus accumbens (NAc). The enhanced dopaminergic tone drives biased activation of dopamine-receptor-1-expressing medium spiny neurons (D1-MSNs) in NAc and reverses anhedonia in chronically stressed animals. Collectively, these findings suggest the therapeutic potential of propofol against anhedonia, which warrants future clinical investigations.

Propofol misuse in medical professions: a scoping review

PURPOSE

We aimed to describe the current literature concerning propofol misuse in medical professionals, specifically relating to the individual demographics of those misusing propofol and the outcomes of propofol misuse.

METHODS

We conducted a retrospective scoping review of the literature using a modified PRISMA approach. We used MEDLINE, EMBASE, and PsycINFO databases to identify relevant studies based on search terms. Studies describing individual medical professionals misusing propofol were included.

RESULTS

Twenty-four articles describing 88 individual cases of propofol misuse were included for data charting and analysis. Anesthesiologists and certified registered nurse anesthetists were most commonly identified. Death was a common method of identification of misuse, while rehabilitation and death were common final outcomes associated with propofol misuse.

CONCLUSIONS

Despite knowledge of the pharmacokinetic and pharmacodynamic properties of propofol by those misusing this medication, death was a common outcome reported in the literature. Data related to long-term outcomes including re-entry to clinical practice or success of rehabilitation were limited.

Lethal self-administration of propofol and atracurium

Acute propofol intoxications appear rare and remain primarily related to the acquisition of the material from the hospital. In this study, two cases of suicide following self-administration of a propofol-atracurium combination are presented as well as other propofol-related fatalities, in order to investigate propofol postmortem blood concentrations and circumstances surrounding death. The two case studies involved a 48-years-old male and a 61-year-old female, both anesthesiologists, who were found unresponsive with drugs (propofol, atracurium for both, and cisatracurium for one of them) discovered at the scene. Toxicological analyses were performed using validated chromatographic methods and highlighted the presence of propofol (1.0 µg/ml), laudanosine (0.2 µg/ml), paroxetine (3.4 µg/ml), and ethanol (12 mg/dl) for the first case and propofol (1.9 µg/ml), laudanosine (1.2 µg/ml), and hydroxyzine (0.03 µg/ml) for the second case. In the literature, 14 publications describing 27 cases of propofol-related lethal intoxications were identified. Except for two cases, all these fatalities involved healthcare professionals. Accidental overdose was the most frequently reported manner of death and the reported propofol blood concentrations ranged from 0.026 to 223.8 µg/ml. These cases, in agreement with other reported cases, highlight the concerns related to the misuse of hospital-based medicines, especially by health-care professionals, and so, the need for a much more stringent internal control of such drugs.

Presence of Inhibitory Glycinergic Transmission in Medium Spiny Neurons in the Nucleus Accumbens

It is believed that the rewarding actions of drugs are mediated by dysregulation of the mesolimbic dopaminergic system leading to increased levels of dopamine in the nucleus accumbens (nAc). It is widely recognized that GABAergic transmission is critical for neuronal inhibition within nAc. However, it is currently unknown if medium spiny neurons (MSNs) also receive inhibition by means of glycinergic synaptic inputs. We used a combination of proteomic and electrophysiology studies to characterize the presence of glycinergic input into MSNs from nAc demonstrating the presence of glycine transmission into nAc. In D1 MSNs, we found low frequency glycinergic miniature inhibitory postsynaptic currents (mIPSCs) which were blocked by 1 μM strychnine (STN), insensitive to low (10, 50 mM) and high (100 mM) ethanol (EtOH) concentrations, but sensitive to 30 μM propofol. Optogenetic experiments confirmed the existence of STN-sensitive glycinergic IPSCs and suggest a contribution of GABA and glycine neurotransmitters to the IPSCs in nAc. The study reveals the presence of glycinergic transmission in a non-spinal region and opens the possibility of a novel mechanism for the regulation of the reward pathway.

Metabolic Profiles of Propofol and Fospropofol: Clinical and Forensic Interpretative Aspects

Propofol is an intravenous short-acting anesthetic widely used to induce and maintain general anesthesia and to provide procedural sedation. The potential for propofol dependency and abuse has been recognized, and several cases of accidental overdose and suicide have emerged, mostly among the health professionals. Different studies have demonstrated an unpredictable interindividual variability of propofol pharmacokinetics and pharmacodynamics with forensic and clinical adverse relevant outcomes (e.g., pronounced respiratory and cardiac depression), namely, due to polymorphisms in the UDP-glucuronosyltransferase and cytochrome P450 isoforms and drugs administered concurrently. In this work the pharmacokinetics of propofol and fospropofol with particular focus on metabolic pathways is fully reviewed. It is concluded that knowing the metabolism of propofol may lead to the development of new clues to help further toxicological and clinical interpretations and to reduce serious adverse reactions such as respiratory failure, metabolic acidosis, rhabdomyolysis, cardiac bradyarrhythmias, hypotension and myocardial failure, anaphylaxis, hypertriglyceridemia, renal failure, hepatomegaly, hepatic steatosis, acute pancreatitis, abuse, and death. Particularly, further studies aiming to characterize polymorphic enzymes involved in the metabolic pathway, the development of additional routine forensic toxicological analysis, and the relatively new field of ‘‘omics” technology, namely, metabolomics, can offer more in explaining the unpredictable interindividual variability.

Abuse potential assessment of propofol by its subjective effects after sedation

Objective: In this study, we examined the euphoric effect of propofol and its high satisfaction ratio regarding its liability to be abused, particularly in painless procedures, such as colonoscopy.

Methods: Fifty subjects aged between 18 and 65 years who fulfilled the criteria for ASA 1-2 and were prepared for colonoscopy were enrolled into this study. For intravenous sedation induction, 2 mg/kg propofol was used, and additional injections were administered according to BIS values. After colonoscopy, the subjects were taken to a recovery room and observed for 30 minutes. Patients were interviewed with the modified Brice questionnare regarding the incidence and the content of dreams. A 5-point Likert scale was used to classify their dreams, and the content of the dreams was also recorded. To assess the subjective effects of propofol, the patients were asked to use the Hall and Van der Castle emotion scale; their biological states were also assessed. The patients’ feelings regarding propofol were each rated as absent or present. We used the Morphine-Benzedrine Group scale to measure the euphoric effects of propofol. At the end of the study, subjects scored their satisfaction on a five-point scale.

Results: There were no statistically significant differences in sex age, weight, propofol dose, or satisfaction ratio (p>0.05) in the groups, although male patients received a higher dose of propofol and had higher satisfaction ratio. Patients reported no residual after-effects. The incidence of dreaming was 42%. There was no statistically significant difference in dreaming between the sexes, but male patients had a higher dreaming ratio. Dreamers received higher propofol doses and had a higher satisfaction ratio (p>0.05). All dreamers reported happy dreams regarding daily life, and their mean MBG score was 10.5. There was no correlation between MBG scores and propofol doses (r= -0.044, p= 0.761).

Conclusions: We conclude that propofol functions as a reward; that patients enjoy its acute effects; and that no residual after-effects should arise. We suggest that propofol may carry potential for abuse, and further abuse liability testing is indicated.

Coadministration of the AMPAKINE CX717 with propofol reduces respiratory depression and fatal apneas

BACKGROUND

Propofol (2,6-diisopropylphenol) is used for the induction and maintenance of anesthesia in human and veterinary medicine. Propofol's disadvantages include the induction of respiratory depression and apnea. Here, the authors report a clinically feasible pharmacological solution for reducing propofol-induced respiratory depression via a mechanism that does not interfere with anesthesia. Specifically, they test the hypothesis that the AMPAKINE CX717, which has been proven metabolically stable and safe for human use, can prevent and rescue from propofol-induced severe apnea.

METHODS

The actions of propofol and the AMPAKINE CX717 were measured via (1) ventral root recordings from newborn rat brainstem-spinal cord preparations, (2) phrenic nerve recordings from an adult mouse in situ working heart-brainstem preparation, and (3) plethysmographic recordings from unrestrained newborn and adult rats.

RESULTS

In vitro, respiratory depression caused by propofol (2 μM, n = 11, mean ± SEM, 41 ± 5% of control frequency, 63 ± 5% of control duration) was alleviated by CX717 (n = 4, 50-150 μM). In situ, a decrease in respiratory frequency (44 ± 9% of control), phrenic burst duration (66 ± 7% of control), and amplitude (78 ± 5% of control) caused by propofol (2 μM, n = 5) was alleviated by coadministration of CX717 (50 μM, n = 5). In vivo, pre- or coadministration of CX717 (20-25mg/kg) with propofol markedly reduced propofol-induced respiratory depression (n = 7; 20mg/kg) and propofol-induced lethal apnea (n = 6; 30 mg/kg).

CONCLUSIONS

Administration of CX717 before or in conjunction with propofol provides an increased safety margin against profound apnea and death.

Suicide by self-administration of a drug mixture (propofol, midazolam, and zolpidem) in an anesthesiologist: the first case report in Italy

The authors report an unusual case of suicide of an anesthesiologist, in which the suicide manner and means depend upon the victim's occupation. This is the first case report published in Italy of a death involving propofol and other drugs. The anesthesiologist was found dead with an empty drip still inserted in the hand and another one near his body. Forensic and toxicological findings suggested that the cause of death was a respiratory depression due to a self-administration of a rapidly infused lethal drug mixture. Analytical drug quantification was performed by gas chromatography-mass spectrometry. Blood analysis revealed: zolpidem (0.86 μg/mL), propofol (0.30 μg/mL), midazolam (0.08 μg/mL), thiopental (0.03 μg/mL), and amitriptyline (0.07 μg/mL). Adipose tissue and hair analysis suggested a previous and repeated use of these drugs verifying the fact that in Italy recreational abuse of anesthetic and sedative agents in health care practitioners is becoming an increasing problem.

The misuse and abuse of propofol

Media attention on the misuse of propofol increased significantly when the drug was implicated in the death of pop music superstar Michael Jackson in 2010. The misuse and abuse of propofol among healthcare providers has been reported worldwide, with some misuse resulting in death. Propofol policies guiding healthcare worker re-entry into the workplace after misusing propofol have received rare attention in the research literature. The paucity of information regarding propofol-specific re-entry policies suggests that little research has addressed this problem and the lack of research and policy guidance can contribute to unsafe re-entry and even death. This paper focuses on healthcare providers because they have an easy access to propofol and therefore are vulnerable to misusing or abusing the drug. To accomplish this, the pharmacology and misuse/abuse potential of propofol and the influence of the 12-step recovery paradigm in the re-entry literature are reviewed. In conclusion, existing research and policy are drawn upon to suggest employment re-entry guidelines for healthcare workers.