Use of Fentanyl in Adolescents with Clinically Severe Obesity Undergoing Bariatric Surgery: A Pilot Study

Background: The number of obese pediatric patients requiring anesthesia is rapidly increasing. Although fentanyl is a commonly used narcotic during surgery, there are no pharmacokinetic (PK) data available for optimal dosing of fentanyl in adolescents with clinically severe obesity.
Materials and Methods: An institutional review board-approved exploratory pilot study was conducted in six adolescents aged 14–19 years undergoing bariatric surgery. Mean total body weight (TBW) and mean BMI were 137.4 ± 14.3 kg and 49.6 ± 6.4 kg/m2 (99.5th BMI percentile), respectively. Fentanyl was administered intravenously for intraoperative analgesia based on ideal body weight per standard of care. PK blood samples were drawn over a 24-h post-dose period. Fentanyl PK parameters were calculated by non-compartmental analysis.
Results: Mean fentanyl AUC0–∞ was 1.5 ± 0.5 h·ng/mL. Systemic clearance of fentanyl was 1522 ± 310 mL/min and 11.2 ± 2.6 mL/min·kg TBW. Volume of distribution was 635 ± 282 L and 4.7 ± 2.1 L/kg TBW. While absolute clearance was increased, absolute volume of distribution was comparable to previously established adult values.
Conclusions: These results suggest that fentanyl clearance is enhanced in adolescents with clinically severe obesity while volume of distribution is comparable to previously published studies.

Study registration: NCT01955993 (clinicaltrials.gov).