Iontophoretic drug delivery system: focus on fentanyl

Fentanyl iontophoretic transdermal system (ITS) is a novel, patient-activated drug delivery device used for the management of acute postoperative pain in the hospital setting. This credit-card-sized device uses an imperceptible current of 170 milliampere to actively deliver a fentanyl hydrochloride 40-microg dose into the vasculature over a 10-minute interval. The unit is programmed to lock out further doses after either 80 doses or 24 hours, whichever is reached first. When comparing fentanyl ITS with intravenously administered fentanyl, serum concentrations differ significantly at 10 minutes after the initial dose is administered: 0.1 ng/ml for fentanyl ITS versus 0.7 ng/ml for intravenous fentanyl. Fentanyl ITS absorption increases in a time-dependent fashion over the first 10 hours of dosing. Other pharmacokinetic parameters of fentanyl ITS are comparable to those of intravenous fentanyl after 24 hours (maximum concentration 1.37 and 1.82 microg/ml, time to maximum concentration 0.65 and 0.58 hr, and area under the concentration-time curve at 23-24 hrs 1.23 and 1.34 microg x hr/ml for fentanyl ITS and intravenous fentanyl, respectively,). This new technology exhibited superior analgesia compared with placebo in two placebo-controlled studies that used time to exit as a primary end point. In addition, fentanyl ITS proved equivalent to patient-controlled analgesia with intravenous morphine. Although adverse effects were congruent with those expected from pure-agonist opioids, subjects assigned to the ITS group did experience a higher rate of mild, clinically nonsignificant erythema at the system placement site. Judicious monitoring for opioid-induced respiratory depression is recommended for fentanyl ITS, although this adverse effect has not been observed in clinical trials. Fentanyl ITS may provide another useful alternative in the management of acute postoperative pain.