Evaluation of the bioequivalence of two transdermal fentanyl systems following single and repeat applications

OBJECTIVE: Transdermal delivery of fentanyl has potential benefits over slow-release morphine, being largely preferred by patients owing to the combination of effective pain relief, a good safety profile and easy, pain-free dosing. The new drug-in-adhesive Durogesic D-TRANS fentanyl Matrix Delivery System (DDTDF) has improved pharmaceutical characteristics and patient acceptability compared to the original Durogesic transdermal reservoir system (fentanyl transdermal reservoir), whilst still providing reliable and consistent delivery of fentanyl. The bioequivalence of these two systems was evaluated in two studies. RESEARCH DESIGNS AND METHODS: Eighty healthy volunteers received single (72 h) or multiple (288 h) applications of DDTDF and the transdermal reservoir system (100 microg/h) in two separate randomised, crossover bioequivalence studies. Bioequivalence was assessed by calculating the ratio of least squares means based on log-transformed data following single system application and at steady-state during the fourth application. RESULTS: Both transdermal systems were bioequivalent with respect to all tested pharmacokinetic parameters. Inter-subject variability was comparable between the two systems and was greater than intra-subject variability. Transdermal delivery was well tolerated in both groups. CONCLUSIONS: The pharmacokinetic results demonstrate that DDTDF is bioequivalent to the original fentanyl transdermal reservoir system after single and multiple applications.