High Body Mass Index and Use of Fentanyl Iontophoretic Transdermal System in Postoperative Pain Management: Results of a Pooled Analysis of Six Phase 3/3B Trials.

INTRODUCTION: Postoperative pain management can be challenging in patients with a high body mass index (BMI) especially as a result of poor venous access and delayed ambulation that can result in serious complications. Fentanyl iontophoretic transdermal system (ITS) is a needle-free, patient-controlled analgesic method available for use in acute postoperative pain. The primary objective of these analyses was to determine if there were any differences between patients with high BMI (>40 kg/m2 ) and lower BMIs (<30 kg/m2 and 35-40 kg/m2 ) in terms of efficacy or safety.

METHODS: Data from three registration, placebo-controlled trials and three active-comparator trials using fentanyl ITS (IONSYS® , The Medicines Company, Parsippany, NJ) for the management of postoperative pain were analyzed using BMI categories of <35 kg/m2 , 35-40 kg/m2 , and >40 kg/m2 . The majority of patients had lower abdominal or orthopedic surgery. For these analyses, the primary efficacy variables were assessed via patient global assessment of pain control (PGA) at 24 h and investigator global assessment (IGA) at study discharge. PGA and IGA are categorical 4-point scales (excellent, good, fair, or poor) with treatment "success" defined as either excellent or good. Safety was evaluated via treatment emergent adverse events (TEAEs).

RESULTS: There were 1403 patients randomly assigned and treated with fentanyl ITS for at least 3 h (BMI <35 kg/m2 : 1180; 35-40 kg/m2 : 136, BMI >40 kg/m2 : 85; and 2 missing). PGA treatment success, which evaluates the method of pain control, at 24 h was consistent in the high and low BMI groups in patients treated with fentanyl ITS (<35 kg/m2 : 946/1180 [80.2%]; 35-40 kg/m2 : 103/136 [75.7%]; and >40 kg/m2 : 65/85 [76.5%]). The IGA results at study discharge were similar to the PGA. Safety appeared similar with fentanyl ITS across the BMI groups.

CONCLUSION: In these analyses, fentanyl ITS was as efficacious, as assessed by the PGA ratings of treatment "success", in patients with high BMI (>40 kg/m2 ) as it was for those with lower BMIs (<35 kg/m2 or 35-40 kg/m2 ) and was generally well tolerated across all BMI categories.