Pharmacokinetics of Nasal Fentanyl

Objective: To investigate the pharmacokinetics of intranasal fentanyl in adult post‐operative female patients. Method: Patients received both intravenous and intranasal fentanyl (approximately 50 µg) in a randomised cross‐over study. Results: Pharmacokinetic data sets from 19 patients showed intranasal fentanyl produced plasma levels within the therapeutic range within two minutes, with median bioavailability values of 55 % (pH 6 formulation) and 71% (pH 8 formulation) . Mean peak serum concentrations were 0.33 ng/mL (pH 6) and 0.37 ng/mL (pH 8) respectively, compared with 2.33 ng/mL after intravenous fentanyl. Conclusion: We conclude that the absorption of intranasal fentanyl is rapid, the bioavailability more than half that of intravenous administration and that the formulations studied are suitable for more extensive clinical evaluation.