Assessment of abuse potential of furanylfentanyl and tetrahydrofuranylfentanyl.

RATIONAL: Furanylfentanyl and tetrahydrofuranylfentanyl (THF-F) have been emerging in numerous intoxication and overdose cases in recent years. However, there remains a data deficiency regarding the abuse potential of these novel fentanyl analogs.

OBJECTIVES

This study was designed to systematically assess the abuse potential of furanylfentanyl and THF-F.

METHODS

In this study, we evaluated the abuse potential of furanylfentanyl and THF-F via the conditioned place preference (CPP), drug self-administration, drug discrimination, and naloxone-precipitated withdrawal experiments with fentanyl as a reference.

RESULTS

Results from CPP experiments indicated that furanylfentanyl and THF-F could induce CPP at minimum doses of 0.1 mg/kg and 3 mg/kg, respectively. These doses were 1 time and 30 times that of fentanyl (0.1 mg/kg). Furanylfentanyl elicited stable self-administration responses at 2.5 µg/kg/infusion, whereas THF-F did so at 50 µg/kg/infusion. In the drug-substitution test, furanylfentanyl and THF-F induced the maximum number of infusions at 1.10 µg/kg and 12.5 µg/kg, respectively, which were 1 time and 10 times that of fentanyl (1.21 µg/kg). In drug discrimination tests, all three substances were fully substituted for the discriminative-stimulus effects of heroin dose-dependently. The substitution potency of furanylfentanyl (ED50 = 2.68 µg/kg) was similar to that of fentanyl (ED50 = 2.66 µg/kg), while THF-F (ED50 = 36.32 µg/kg) was 14-fold less potent than fentanyl. Repeated administration of furanylfentanyl and THF-F produced naloxone-precipitated withdrawal symptoms. Thus, furanylfentanyl exhibited comparable potency to fentanyl in terms of rewarding, reinforcing, and subjective effects, while THF-F had reduced potency in these effects. Both of them had physical dependence.

CONCLUSIONS

Taken together, our study presented new evidence indicating that furanylfentanyl and THF-F exhibit significant abuse potential in rodent models, which provides experimental data for the control. Furthermore, our study offered valuable information for future studies into the addictive properties of structurally modified fentanyl analogs.