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.