FENTANYL DELIVERY FROM AN ELECTROTRANSPORT SYSTEM - DELIVERY IS A FUNCTION OF TOTAL CURRENT, NOT DURATION OF CURRENT

This open-label, parallel study of 28 men was conducted to evaluate th e pharmacokinetics and safety of fentanyl delivered by the E-TRANS (fe ntanyl) electrotransport transdermal system (ALZA Corporation, Pale Al to, CA). The E-TRANS (fentanyl) system provided electrically assisted, transdermal, continuous delivery of fentanyl. Treatments consisted of no current (group A); a constant current of 100 mu A for 26 hours plu s 4 additional doses at varying currents for varying times during hour 25 (groups B, C, D); a constant current of 100 mu A for 26 hours plus 4 additional doses at 1,200 mu A over 2.5 minutes during hour 1 (grou p E); or 500 mu A for 0.5 hours and 100 mu A for 3.5 hours (group F). No fentanyl was detected in serum when no current had been applied. Me an serum fentanyl concentrations were similar regardless of current du ration during hour 25 (treatments B, C, D). Increases in mean serum fe ntanyl concentrations were significantly lower during additional dosin g for treatment E compared with treatments B, C, and D. Serum fentanyl concentrations sufficient for analgesia (1-3 ng/mL) were attained in treatments using the E-TRANS (fentanyl) system with basal current of 1 00 mu A for 26 hours. There were no safety issues after treatment with E-TRANS (fentanyl) system with concurrent opioid antagonist (naltrexo ne) administration. The only adverse event requiring treatment was a h eadache (n = 1). The majority of subjects had no or barely perceptible erythema at the application site 24 hours after system removal. Appli cation of E-TRANS (fentanyl) resulted in therapeutically significant s erum fentanyl concentrations over a range of applied currents. Overall serum fentanyl concentrations were higher when the skin had been prim ed by constant-current fentanyl delivery.