Results: The pharmacokinetics of intravenous fentanyl reflected a 2-compartment model with a clearance of ... to approximately 240 minutes (200 µg) after a single dose. Conclusions: Intranasal ...

As found in the separate modeling of the intravenous and nasal data, the 2-compartment model with an estimated bioavailability and an absorption lag for the nasal route was the best fit of the data.