Comparison of Equivalent Doses of Fentanyl Buccal Tablets and Arteriovenous Differences in Fentanyl Pharmacokinetics
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The fentanyl buccal tablet (FBT) is designed to enhance the rate and extent of fentanyl absorption through the buccal mucosa.
To evaluate the bioequivalence of μg-equivalent doses of FBT administered as single and multiple tablets and assess differences in the arterial and venous pharmacokinetics of FBT in healthy volunteers.
Twenty-seven healthy adults, aged 19–5 years, participated in the randomised, open-label, three-period, crossover study. In the first two periods, FBT was administered as four 100μg tablets simultaneously or one FBT 400μg to assess bioequivalence. Venous blood samples were obtained over a 72-hour period to measure plasma fentanyl concentrations. In the third period, arterial and venous blood samples were obtained simultaneously from before administration of one FBT 400μg through 4 hours after administration to evaluate the impact of arterial versus venous sampling on the pharmacokinetic profile. As subjects were not opioid tolerant, naltrexone was administered to block opioid receptor-mediated effects of fentanyl. Adverse events were recorded throughout.
Maximum plasma concentration (Cmax) and area under the plasma concentration-time curve from time zero to infinity (AUC∞) on average were approximately 12% and 13% higher, respectively, for FBT administered as four 100μg tablets simultaneously compared with one FBT 400μg. Maximum plasma concentrations in the arterial circulation were approximately 60% higher and occurred 15 minutes earlier than those measured from the venous circulation. No serious adverse events were reported during the study.
Despite small differences in Cmax and AUC∞ (on average 12% and 13%, respectively), FBT administered as four 100μg tablets simultaneously compared with one 400μg tablet did not meet the criteria for bioequivalence. An increased surface area exposure with four tablets compared with one tablet may account for the slightly higher maximum concentrations observed with four 100μg tablets. A substantially higher Cmax was reached earlier in the arterial than in the venous circulation.
KeywordsFentanyl Naltrexone Venous Sampling Breakthrough Pain Arterial Circulation
This study was supported by Cephalon, Inc. (Frazer, PA, USA). The authors are employed by the sponsoring company and have no other financial interests or conflicts of interest to disclose. The authors would also like to thank James C. Kisicki, MD and the staff at MDS Pharma Services (Lincoln, NE, USA) for help in carrying out this study.
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