Assessing the impact of heat on the systemic delivery of fentanyl through the transdermal fentanyl delivery system

Objectives. To examine the effects of locally applied heat on the systemic delivery of fentanyl through the Transdermal Fentanyl Delivery System. Design. Open, 2-period crossover randomized study conducted in the anesthes ia department of a university teaching hospital. Method. Six healthy adult volunteers received a fentanyl 25-mug/h patch wit h and without local heat for 240 minutes followed by administration without heat for an additional 20 hours. Participants then crossed over. Venous bl ood was drawn at baseline and hourly for 24 hours. Peak plasma concentratio n (CMax) of fentanyl was measured and the area under the curve (AUC) of the plasma fentanyl concentration versus time post administration graph was ev aluated. Results. Difference in CMax and AUC were not statistically significant over the entire 24-hour study period. However, for the 4-hour period of heat ap plication statistically significant differences were seen in both mean CMax (heat, 0.4 ng/mL versus no heat, 0.1 ng/mL (P =.030)) and mean AUC (heat, 10 ng/mL min versus no heat, 10 ng/mL min (P =.010)). Conclusion. Local heat can speed the onset of steady state fentanyl concent ration in the Fentanyl Transdermal Drug Delivery System(TM) thus limiting t he delay in onset of analgesia and allowing earlier identification and trea tment of side effects.