No correlation between pain and in vitro myotoxicity after intramuscular injection of three cephalosporins

The in vitro myotoxicity of cefonicid, cefoxitin, and cefamandole was evaluated using a validated isolated rodent skeletal muscle model and compared with the results of a previous investigation examining the incidence and duration of pain after intramuscular injection of these cephalosporins into patients. Cefonicid was shown to be more myotoxic than cefamandole and cefoxitin. All three cephalosporins were more myotoxic than the intramuscular injection of normal saline. There was no apparent correlation between the severity or incidence of pain and the in vitro myotoxicity of these three cephalosporins. This lack of correlation between pain and damage could result from local toxic effects of these cephalosporins on other tissues (eg, blood vessels or nerves) at the site of injection.