Background: Illicitly manufactured fentanyl and its analogs are a major driving force behind the ongoing opioid crisis. Cyclopropylfentanyl is a fentanyl analog associated with many overdose deaths, but limited knowledge is available about its pharmacology. In the present study, we developed a bioanalytical method for the determination of cyclopropylfentanyl and its main metabolite cyclopropylnorfentanyl and evaluated pharmacokinetic-pharmacodynamic relationships in rats.
Method: An ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) method was developed and validated for determination of cyclopropylfentanyl and cyclopropylnorfentanyl in rat plasma. Male Sprague-Dawley rats fitted with jugular catheters and temperature transponders received cyclopropylfentanyl (30, 100, and 300 μg/kg) or saline subcutaneously. Blood specimens were withdrawn over an 8-h time period, along with measurements of pharmacodynamic endpoints.
Results: The analytical method was validated, and both analytes exhibited a low limit of quantification (15 pg/mL). Cyclopropylfentanyl caused dose-related increases in hot plate latency (ED = 48 µg/kg) and catalepsy (ED = 87 µg/kg) and produced long-lasting hypothermia at the highest dose. Plasma cyclopropylfentanyl rose rapidly in a dose-related fashion, reaching maximal concentration (C) after 15-28 min, whereas metabolite Cmax occurred later at 45-90 min. Cyclopropylfentanyl C values were similar to concentrations measured in non-fatal intoxications in humans; however, differences in parent drug: metabolite ratio indicated possible interspecies variance in metabolism.
Conclusion: Our study shows that cyclopropylfentanyl produces typical opioid-like effects in male rats. Cyclopropylfentanyl displays much greater analgesic potency when compared to morphine, suggesting that cyclopropylfentanyl poses increased overdose risk for unsuspecting users.
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| http://dx.doi.org/10.1007/s00213-021-05981-x | DOI Listing |
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