MSACL 2024 Abstract

Case Description:
A 31-year-old male with a past medical history of psychosis and methamphetamine and fentanyl use disorder became unresponsive after injecting an unknown drug. Bystanders started cardiopulmonary resuscitation without success. When emergency medical services arrived, he was apneic with a blood oxygen saturation of 58% (normal 95-100%), a strong pulse, blood pressure of 123/82, and Glasgow Coma Scale (GCS) of 3 (<8, severe brain injury). He was ventilated with a bag valve mask and received Narcan (2 mg intranasal, 2 mg intramuscular, 0.4 mg intravascular x2) in the field with minimal response. In the emergency department, he was breathing spontaneously, however his GCS remained at 3. He received an additional dose of Narcan (2 mg intravascular x2) without improvement, was intubated for airway protection, and transferred to the intensive care unit for further management. The urine toxicology results by immunoassay were positive for amphetamines and fentanyl. A comprehensive drug test by liquid chromatography quadrupole time of flight mass spectrometry (LC-QTOF-MS) conducted at the time of presentation, identified fentanyl, norfentanyl, methamphetamine, olanzapine (a second-generation atypical antipsychotic medication), and flubromazepam, a non-FDA approved designer benzodiazepine. The patient remained in the ICU for 3 days. After extubation, he had disorganized tangential speech with odd behavior leading to concern for anoxic brain injury. His hospital course was complicated by significant acute liver ischemia due to prolonged hypoxia. The final discharge diagnosis was fentanyl and flubromazepam overdose.

Background:
Benzodiazepines are central nervous system depressants prescribed to relieve anxiety, producing drowsiness and a relaxed mood. However, there is a risk of fatal overdose, especially when consumed in combination with other depressants (e.g., opioids and alcohol). Common FDA-approved benzodiazepines include alprazolam, lorazepam, and diazepam, which in the United States require a prescription for legal access. In the wider context of a highly variable illicit substance supply, non-FDA approved benzodiazepines (designer benzodiazepines) have emerged. These illicit products present a clear overdose risk, as unsuspecting consumers may be exposed to unexpected benzodiazepines of highly variable potencies and pharmacokinetic profiles. With similar chemical structures, previous clinical studies have found it difficult to differentiate designer from prescription benzodiazepines. Also, there are detection limitations, specifically with flubromazepam (a designer benzodiazepine), as its cross-reactivity has varied in immunoassays. Of note, the benzodiazepine immunoassay screen was negative in the case presented here. Animal studies suggest flubromazepam is more potent than commonly prescribed benzodiazepines and has the potential for dependence. To date, there is one study on the pharmacokinetics of flubromazepam after low-dose oral consumption by one study participant. This study suggested that flubromazepam has a long elimination half-life of >100 hours. This clinical case presented an opportunity to better understand the pharmacokinetics of flubromazepam following a presumed overdose via injection over 66 hours (time in the hospital).

Methods:
Eight remnant serum samples over 66 hours after exposure were collected after routine clinical testing was complete. Serum concentrations of flubromazepam and fentanyl were quantitated using a clinically validated comprehensive drug test by untargeted LC-QTOF-MS. Data was collected on a SCIEX TripleTOF®5600 operating in positive-ion mode using a TOF-MS survey scan with IDA-triggered collection of high-resolution product ion spectra (20 dependent scans). Quantitation for fentanyl and flubromazepam was performed using 13 calibrators, a double blank, a blank, and 4 quality controls prepared in drug-free human serum to cover a dynamic range from 0.1 ng/mL to 600 ng/mL. The internal standard was a mix of fentanyl-D5, diazepam-D5, and methamphetamine-D5 at 1 µg/mL. Samples were prepared by protein precipitation followed by centrifugation. Sample supernatant was evaporated under a steady stream of nitrogen gas then reconstituted in starting mobile phase conditions.

Results:
The serum samples were collected at the following timepoints relative to presumed time of exposure: 1, 5, 16, 29, 40, 48, 55, and 66 hours. For these timepoints, the flubromazepam concentrations were: 39, 37, 67, 66, 79, 80, 72, and 56 ng/mL, and the fentanyl concentrations were: 6.4, 0.5, 0.9, 0.3, 0.1, 0.1, 0.2, and 0.1 ng/mL.

Discussion and Conclusion:
The flubromazepam concentration was highest in the 48-hour sample following exposure, confirming previous data that suggests a long terminal half-life (>100 hours). The highest concentration was 80 ng/mL. This is the first concentration determined in a case of suspected overdose with hospital admission and may inform future cases of exposure. The concentration was still 56 ng/mL 66 hours after exposure. Serum concentrations of fentanyl >7 ng/mL have been associated with fatalities where poly-substance use was involved. In this case, the serum fentanyl concentration approximately 1 hour after exposure was 6.4 ng/mL. Given that the patient likely had developed a tolerance to fentanyl, this fentanyl concentration alone likely does not fully explain the clinical presentation in this case. This is supported by the patient’s limited response to repeated administration of naloxone. The identification of flubromazepam by LC-QTOF-MS provided the likely cause of the prolonged clinical course that could not be explained by fentanyl exposure alone. Of note, traditional immunoassay-based methods were not informative for the final discharge diagnosis for this patient. Comprehensive drug testing by LC-QTOF-MS in the clinical laboratory provides additional insight into complicated cases of poly-drug exposure.