title: Assessing the impact of heat on the systemic delivery of fentanyl through the transdermal fentanyl delivery system.
abstract: OBJECTIVE
  To examine the effects of locally applied heat on the systemic delivery of fentanyl through the Transdermal Fentanyl Delivery System.
  
  
  METHODS
  Open, 2-period crossover randomized study conducted in the anesthesia department of a university teaching hospital.
  
  
  METHODS
  Six healthy adult volunteers received a fentanyl 25-microg/h patch with and without local heat for 240 minutes followed by administration without heat for an additional 20 hours. Participants then crossed over. Venous blood was drawn at baseline and hourly for 24 hours. Peak plasma concentration (CMax) of fentanyl was measured and the area under the curve (AUC) of the plasma fentanyl concentration versus time post administration graph was evaluated.
  
  
  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 application 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, 40 ng/mL x min versus no heat, 10 ng/mL x min (P =.010)).
  
  
  CONCLUSIONS
  Local heat can speed the onset of steady state fentanyl concentration in the Fentanyl Transdermal Drug Delivery System thus limiting the delay in onset of analgesia and allowing earlier identification and treatment of side effects.
authors.affiliation: Department of Anesthesiology, University of Utah School of Medicine, Salt Lake City 84132, USA.
authors.forename: T S
authors.initials: TS
authors.lastname: Shomaker
authors.forename: J
authors.initials: J
authors.lastname: Zhang
authors.forename: M A
authors.initials: MA
authors.lastname: Ashburn