Extending the safety profile of the post-operative administration of an intravenous acetaminophen/ibuprofen fixed dose combination: An open-label, multi-center, single arm, multiple dose study.

Purpose: Postoperative pain is typically treated with multimodal analgesia, using systemic acetaminophen and/or nonsteroidal anti-inflammatory drugs in conjunction with opioids as required. The present study aimed to determine the safety and tolerability of repeated doses of an intravenous fixed-dose combination (FDC) of acetaminophen and ibuprofen.

Methods: This multicenter, open-label, single arm, multiple dose study was conducted at 4 centers across New Zealand and the United States between July 2019 and July 2020. Adults (>18 years) requiring multiple doses of parenteral nonopioid analgesics over multiple days following non-laparoscopic general, plastic or orthopedic surgery were eligible. The study drug (acetaminophen 1000 mg+ibuprofen 300 mg) was administered 6-hourly as a 5 min infusion for between 48 h and 5 days. Adverse event data was collected throughout the study, in addition to scheduled vital sign assessments, laboratory tests and electrocardiograms. Participants completed a global evaluation of the FDC at the end of the treatment period.

Findings: 232 participants received ≥ 1 dose of the FDC. Most were female (62.1%), White (56.5%) or Black or African American (39.2%), and had undergone orthopedic surgery (85.3%). There was a broad age range (19-87 years), with a mean age of 53.4 years, and 26.3% of participants aged ≥ 65 years. The FDC was safe when used for 48 h to 5 days. Treatment-emergent adverse events (TEAEs) affected 56.0% of participants, the most common were infusion site pain, nausea, infusion site extravasation, constipation, and headache. Minimal changes in vital signs were observed at scheduled timepoints. No clinically significant changes in electrocardiogram assessments occurred. Transient elevations in the hepatic enzymes ALT and AST to < 3 times the upper limit of normal (ULN) affected 10.5% and 9.6% of subjects, elevations to ≥ 3 times the ULN affected 2.6% and 2.2% of subjects, respectively. There were no apparent differences in the safety profile of the FDC in older participants. The FDC was well tolerated; most TEAEs were mild or moderate in severity. Five participants discontinued treatment due to TEAEs, none were considered treatment-related. The FDC was perceived well by study participants; the majority rated their experience as 'excellent' (40.1%) or 'very good' (35.3%).

Implications: The safety profile was comparable to previous studies with no novel safety concerns. The FDC was safe, well tolerated, and perceived positively by participants treated for acute pain between 48 h and 5 days following orthopedic or plastic surgery, supporting a favorable risk benefit profile.