The concentration of lidocaine and mepivacaine measured in synovial fluid of different joints of horses after single intra-articular injection.
Authors: Adler Ditte M T, Jørgensen Elin, Cornett Claus
Journal: Frontiers in veterinary science
Summary
# Editorial Summary Intra-articular local anaesthetics are widely used in equine lameness diagnosis and treatment, yet little is known about their actual concentrations within synovial fluid or how these vary between different joints. Adler and colleagues measured lidocaine and mepivacaine concentrations in synovial fluid samples collected from four clinically important joints (distal interphalangeal, metacarpophalangeal, middle carpal, and tarsocrural) at two timepoints following single intra-articular injection of clinically relevant doses. Their findings revealed substantial variation in drug concentrations both between different joints and over time, with some joints achieving markedly higher synovial fluid levels than others—data the researchers then compared directly against known thresholds for cytotoxicity and antimicrobial activity. These results have meaningful implications for practitioners selecting between lidocaine and mepivacaine based on joint location and therapeutic intent; joints achieving higher local concentrations may offer greater antimicrobial benefit in septic arthritis cases, whilst practitioners must balance this against potential chondrotoxicity risks, particularly where prolonged contact or repeated injections are planned. Understanding these pharmacokinetic differences enables more evidence-based decision-making around drug choice and dosing strategy for individual joints rather than applying a one-size-fits-all approach to intra-articular local anaesthetic use.
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Practical Takeaways
- •Local anesthetic choice and dose may need to be tailored by joint type to balance anesthesia efficacy against potential cytotoxic effects on synovial tissues
- •Understanding synovial fluid concentrations helps predict safety margins and duration of anesthetic effect for different intra-articular injections in clinical practice
- •Results support evidence-based dosing protocols for joint anesthesia across commonly treated equine joints
Key Findings
- •Lidocaine and mepivacaine concentrations in synovial fluid vary significantly between different joint types after single intra-articular injection
- •Study measured drug concentrations at two time points post-injection to determine relationship with previously established cytotoxic and antimicrobial thresholds
- •DIP, MCP, MC, and TC joints show different pharmacokinetic profiles for both local anesthetics