Uptake pharmacokinetics of the Fentanyl Oralet in children scheduled for central venous access removal: implications for the timing of initiating painful procedures.

BACKGROUND: The Fentanyl Oralet (Abbott Laboratories, Abbott Park, IL, USA) is an oral transmucosal drug delivery system. We previously examined pharmacokinetic parameters of children who had completed consumption of the Fentanyl Oralet. The present study was designed to clarify pharmacokinetic parameters during the consumption phase to determine if there is an optimal administration time before painful procedures.
METHODS: Patients, aged 3-10 years, who were scheduled for elective removal of central venous access devices under general anaesthesia, received a Fentanyl Oralet (fentanyl 10-15 microg x kg(-1)). Plasma fentanyl concentrations were measured by radioimmunoassay. Data from blood samples obtained during and after consumption of the Fentanyl Oralet from 17 patients in the present study were combined with data from our previous study to better characterize both the consumption and postconsumption concentration versus time profiles.
RESULTS: Estimated fentanyl bioavailability (mean +/- SD) was low (36.1 +/- 0.4%), as were peak plasma concentrations (1.03 +/- 0.31 ng.ml-1), suggesting that many children swallowed a large fraction of the dose. This led to a relatively late and variable peak concentration time of 53 +/- 40 min. In addition, because of the apparently large degree of gastrointestinal absorption, concentration versus time curves were wide and flat.
CONCLUSIONS: The wide and flat concentration versus time profile may allow flexibility in the timing of a painful procedure following Fentanyl Oralet administration. However, the variability of the time to peak concentration makes it difficult to suggest a minimum interval between Fentanyl Oralet consumption and the start of a painful procedure.