Postoperative Pain Management With a Patient-Controlled Transdermal Delivery System for Fentanyl

Peter J. S. Koo

Disclosures

Am J Health Syst Pharm. 2005;62(11):1171-1176. 

In This Article

Pharmacokinetics

The iontophoretic process requires that the hydrochloride salt of fentanyl be used in PCTS. As current flows through the drug-containing anode hydrogel, the fentanyl salt is ionized, and the positively charged fentanyl molecules are repelled from the positively charged anode surface, facilitating fentanyl transport across the skin. Doses delivered from the system are expressed as the amount of ionized fentanyl transferred from the system into the systemic circulation.

When activated, PCTS consistently delivers the preprogrammed 40-µg dose of fentanyl hydrochloride into the systemic circulation at a controlled rate.[28] The amount of drug delivered is independent of dosage frequency[29] and is linearly related to the magnitude of the electric current applied to the system: 170 µA delivers a nominal 40-µg dose of fentanyl hydrochloride.[30]

When healthy volunteers received two sequential 40-µg doses per hour from PCTS for 23.3 hours, the bio-availability of fentanyl delivered increased over time, as approximately 41% of the nominal dose was shown to be absorbed into the systemic circulation after the first hour of treatment and nearly 100% after 10 hours.[29] This increase is not clinically significant, however, because patients can adjust their own medication to achieve a satisfactory level of pain control. The pharmacokinetics of fentanyl delivered by this system remain consistent over multiple-day administration periods; another trial found no significant differences in the area under the corrected serum concentration-versus-time curve after dosage periods of 20 and 68 consecutive hours ( p = 0.133) ( Table 1 ).[30] Demographic characteristics (age, body weight, sex, and ethnicity) have also been shown to have no significant pharmacokinetic effect ( Table 2 ).[31]

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