Each patch contains a 72-hour supply of fentanyl, which is passively absorbed through the skin over this period. Levels in plasma rise slowly over 12 to 18 hours after patch placement, and the dosage form has an elimination half-life of 21 hours. Therefore, unlike intravenous fentanyl, the transdermal administration of fentanyl is not suitable for rapid dose titration (Payne, 1992; Portenoy, Southam, Gupta, et al., 1993). Transdermal fentanyl should be considered when patients have relatively constant pain with infrequent episodes of breakthrough pain such that rapid increases or decreases in pain intensity are not anticipated. As with other long acting analgesics, all patients should be provided with oral or parenteral rapidly acting short duration opioids to manage breakthrough pain (Portenoy and Hagen, 1990). The most commonly reported side effects of transdermal fentanyl administration are nausea, mental clouding, and skin irritation.
Intravenous or Subcutaneous