Efficacy of Naloxone as a Treatment for an Acute Exposure to Aerosolized Carfentanil

Abstract

Carfentanil (CRF) is a powerful synthetic opioid that is approximately 100 times more potent than fentanyl and 10,000 times more potent than morphine. CRF originally was intended to be used as a sedative for big game animals in a veterinary setting, but is becoming increasingly common in the illicit drug trade. The increased use of CRF by people has put strain on first responders, who need to administer increased doses of naloxone (Naracan®, Evzio®), an FDA‐approved opioid antagonist, to counteract the effects. First responders may also worry about the potential of self‐exposure through inhalation or dermal contact with CRF. We set out to study the effectiveness of naloxone against a potentially lethal dose of inhaled CRF in male ferrets. Ferrets were implanted with telemetry devices to study cardiac parameters and exposed to aerosolized CRF in a whole‐body plethysmography chamber to record respiratory parameters. We observed profound depression of respiration which resulted in the animals becoming apneic 23% ± 9% of the time during exposure. We also observed cardiac abnormalities, in the form of premature junctional contractions (PJCs), in the ferrets during the apneic periods. At our acute exposure dose, which was lethal in 9% of our animals, ferrets were unresponsive and incapacitated for 105.6 ± 20.0 minutes following the end of exposure. Naloxone, when administered intramuscularly at human equivalent doses ranging from 4 to 40 mg, significantly reduced the time that ferrets were incapacitated following exposure. Although we saw no significant difference in the reduction of time that the animals were incapacitated between the treatment groups (average times between treatment and revival ranged from 6.5 to 9.7 minutes), higher doses of naloxone did revive a portion of the ferrets quicker than the lower doses (some as soon as 1.5–3.5 minutes post‐treatment). We also observed that naloxone was able to significantly reduce the amount of apneic episodes in CRF‐exposed ferrets and resolved the observed cardiac PJCs. Our results suggest that naloxone is a viable treatment against the effects of a potentially lethal dose of inhaled CRF in ferrets. These data have the potential to inform and aid treatment strategies for an acute inhalation exposure to synthetic opioids.Support or Funding InformationOpinions, interpretations, conclusions, and recommendations are those of the author and are not necessarily endorsed by the US Army. This research complied with the Animal Welfare Act and implementing Animal Welfare Regulations and adhered to the principles noted in The Guide for the Care and Use of Laboratory Animals. This research was supported by DTRA RD‐CB. M.R. and N.A.A. were supported in part by an appointment to the Postgraduate Research Participation Program at the US Army Medical Research Institute of Chemical Defense administered by the Oak Ridge Institute for Science and Education through an interagency agreement between the US Department of Energy and USAMRMC.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.