Potential Utility of Liposome Bupivacaine in Orthopedic Surgery

Wound Healing. The potential effects of liposome bupivacaine on wound healing were evaluated with results from 10 phase 2 and 3 studies.⁶⁸ The assessments, which varied across studies, included clinicians’ overall satisfaction with patient wound healing, wound status assessment (categories included erythema, drainage, edema, and induration), and wound scarring (categories included pigmentation, height, pliability, and vascularity). Clinician-assessed scores reflected high satisfaction with wound healing overall. There were few statistically significant differences in wound status assessments between liposome bupivacaine and the comparators and no statistically significant differences in scarring between liposome bupivacaine and bupivacaine HCl.

The potential of liposome bupivacaine to have adverse intra-articular effects was assessed with drainage samples from patients (n = 23) who had TKA and received liposome bupivacaine (133, 266, 399, or 532 mg) or bupivacaine HCl (150 mg) by wound infiltration near the intra-articular space.^51,65 Only small amounts of bupivacaine were present in drainage fluid collected for 12 hours after liposome bupivacaine administration, comparable to bupivacaine HCl administration.⁶⁵ Currently, the product is not approved for intra-articular use.

Compatibility With Diluents, Other Medications, and Implant Materials

Liposome bupivacaine may be expanded up to a ratio of 1:14 by volume (to a final total volume of 300 mL or a concentration of 0.89 mg/mL) using preservative-free normal (0.9%) sterile saline for injection.¹⁴ It has also been shown in vitro to be compatible with lactated Ringer solution as a diluent.⁶⁹

Liposome bupivacaine should not be admixed with other medications before administration.¹⁴ No formal drug–drug interaction studies have been conducted with liposome bupivacaine, but it has been shown in vitro to be compatible with epinephrine solutions, with certain anti-infective medications (eg, bacitracin, gentamicin, cefazolin, cefuroxime), with certain analgesics (eg, ketorolac, morphine), with an antihypertensive medication (clonidine), with an antihemorrhagic medication (tranexamic acid), and with certain corticosteroids (eg, methylprednisolone, triamcinolone acetonide). These medications may be coadministered in the same location as liposome bupivacaine.⁶⁹

Topical antiseptics (eg, povidone iodine) may be used in surgical procedures involving liposome bupivacaine as long as they are not directly mixed with liposome bupivacaine and are allowed to dry before it is administered. If a topical antiseptic is used for wound irrigation, the wound should be rinsed clear before liposome bupivacaine administration.^14,69

Liposome bupivacaine may be coadministered into the same surgical site immediately after bupivacaine HCl as long as the dose ratio of liposome bupivacaine to bupivacaine HCl is 2:1 or higher. Because of the prolonged-release pharmacokinetic profile of liposome bupivacaine and the potential for increased bupivacaine exposure, bupivacaine HCl should not be administered within 96 hours after administration of liposome bupivacaine.^14,69

In vitro coincubation studies of liposome bupivacaine and other local anesthetics, including ropivacaine, lidocaine, and mepivacaine, have found rapid release of free bupivacaine from the liposome matrix. Therefore, after giving any of these other local anesthetics, surgeons should wait at least 20 minutes before administering liposome bupivacaine into the same area.^14,69

In vitro studies have shown that liposome bupivacaine is compatible with a wide range of commonly used implant materials, including polypropylene, expanded polytetrafluoroethylene, stainless steel, titanium, and smooth- and textured-type silicone.⁶⁹

Investigational Use and Ongoing Studies

A phase 2 randomized, double-masked, dose-escalating/deescalating study was conducted to evaluate the efficacy, safety, and pharmacokinetics of liposome bupivacaine (155, 199, or 310 mg) in comparison with bupivacaine HCl 125 mg for ankle nerve block in patients undergoing bunionectomy (N = 58).⁷⁰ The study medication was injected into 3 sites to reach the posterior tibial, sural, deep peroneal, superficial peroneal, and saphenous nerves. Pharmacokinetic exposure was higher for liposome bupivacaine than for bupivacaine HCl, as reflected by a significantly greater area under the curve, lower C_max (maximum serum concentration), and longer mean half-life. Mean pain intensity scores were lower in the bupivacaine HCl group than in each liposome bupivacaine group the first 12 hours after surgery. However, the liposome bupivacaine 310-mg group had similar or lower scores than the bupivacaine HCl group from 12 to 96 hours after surgery. The most common AEs in the liposome bupivacaine group were gastrointestinal and not treatment-related.⁷⁰

The efficacy and safety of liposome bupivacaine, administered as a femoral nerve block for postsurgical analgesia, were assessed in a phase 2/3 manufacturer-sponsored, placebo-controlled, multicenter, randomized, double-blind 2-part study (NCT01683071)⁷¹ in 280 TKA patients.^71,72 Part 2 of the study, comparing liposome bupivacaine 266 mg (n = 116) and placebo (n = 116), met its primary endpoint, demonstrating statistical significance in favor of liposome bupivacaine for cumulative pain scores over 72 hours (P < .0001), with decreased opioid use (P < .05) and a safety profile similar to that of placebo.⁷²