Bupivacaine and Glucocorticoid-Induced Myonecrosis
The most frequently used medications for chronic pain are local anesthetics (LA) and glucocorticoids. Common adverse events from LA, such as seizures and cardiotoxicity, are well known. A lesser known side effect is local tissue reaction to the LA concentration. Myotoxicity is one of the common denominators of direct tissue reaction to LA; it results from the disruption of the mitochondria in the muscle cells. All LA produce some degree of myotoxicity; bupivacaine has the greatest effect and procaine the least. If LA is combined with glucocorticoid, muscle breakdown is even more extensive showing a synergistic effect. Myotoxicity depends primarily on LA concentration, is time dependent, and is enhanced by preexisting altered metabolism. It affects mostly young patients. Potential effects of long-term or repeated administration of the combination LA/glucocorticoids medications should always be considered and discussed with patients.