Physical and Chemical Compatibility of Extended-Release Triamcinolone Acetonide (TA-ER) with Common Local Anesthetics

INTRODUCTION: Intra-articular (IA) corticosteroids are used extensively for the treatment of patients with knee osteoarthritis pain. In clinical practice, local anesthetics are frequently combined with corticosteroids prior to IA injection to provide rapid-onset analgesia. From this common practice there is no evidence to suggest that the addition of local anesthetics to corticosteroid preparations, including triamcinolone acetonide (TA), alters the physical properties or efficacy of the corticosteroid. Triamcinolone acetonide extended-release (TA-ER, formerly FX006) is a novel, microsphere-based TA formulation that demonstrated analgesic efficacy in phase 2 and 3 randomized controlled trials. METHODS: The current study assessed the compatibility of TA-ER and lidocaine, ropivacaine, and/or bupivacaine in vitro. The TA-ER and local anesthetic mixtures were assayed for changes in syringeability, pH, particle size, percentage free drug, purity, and appearance compared with TA-ER alone. RESULTS: By these measures, the combination of local anesthetics with TA-ER did not negatively impact the chemical or physical properties of TA-ER when compared to TA-ER controls. CONCLUSION: These results demonstrate that lidocaine, bupivacaine, and ropivacaine are physically and chemically compatible with TA-ER, suggesting that local anesthetic solutions can be added to TA-ER preparations in clinical practice without adversely affecting TA-ER in vitro product characteristics. FUNDING: Flexion Therapeutics, Inc.