[¹¹C]Fentanyl: Radiosynthesis and Preclinical PET Imaging for Its Pharmacokinetics

Area of Science:

• Radiochemistry
• Pharmacokinetics
• Positron Emission Tomography (PET) Imaging

Background:

• Fentanyl misuse and overdose deaths are major public health concerns.
• Understanding fentanyl's tissue distribution is crucial for its clinical use and safety.
• Current research primarily focuses on plasma concentrations, neglecting critical tissue distribution.

Purpose of the Study:

• To develop and validate [11C]fentanyl for PET imaging.
• To investigate the whole-body pharmacokinetics and tissue distribution of fentanyl in a preclinical rodent model.
• To explore the role of efflux transporters in fentanyl's brain disposition.

Main Methods:

• Automated radiosynthesis of [11C]fentanyl with high radiochemical yield and purity.
• Positron Emission Tomography (PET) imaging in rats to assess whole-body distribution.
• Pharmacokinetic analysis including brain and adipose tissue uptake and washout kinetics.
• Investigated the effect of efflux transporter inhibition/knockout on fentanyl kinetics.

Main Results:

• Successful radiosynthesis of [11C]fentanyl in 42 minutes.
• PET imaging showed rapid brain uptake (SUVmax 2.71±1.04 g/mL) and fast washout (T1/2 = 5.06 min).
• Significant and prolonged uptake in adipose tissue (SUVmax = 1.73±0.313 g/mL, T1/2 = 177 min) with high retention of unchanged fentanyl.
• Efflux transporter inhibition/knockout significantly altered brain kinetics.

Conclusions:

• Automated [11C]fentanyl radiosynthesis enables valuable PET imaging studies.
• PET imaging revealed rapid brain kinetics and the critical role of P-gp/BCRP efflux transporters in fentanyl brain disposition.
• Prolonged adipose tissue retention of fentanyl may delay brain clearance and increase re-narcotization risk.
• This PET tracer is a valuable tool for quantifying fentanyl pharmacokinetics and tissue distribution in preclinical and clinical research.