Changes in plasma enzyme concentrations following intramuscular injections and gastroscopy.

The effects of intramuscular injections on plasma creatine kinase (CK), aspartate amino-transferase, lactate dehydrogenase, and hydroxybutyrate dehydrogenase concentrations were examined in 19 patients given intramuscular premedication for gastroscopy, and 18 patients given other intramuscular injections. Only CK concentrations showed significant increases which were as high as four times the upper limit of normal, and affected a maximum of 51% of patients at 12 hours after the first injection. Elevated CK concentrations persisted for up to 72 hours, and followed injections of diazepam, various antibiotics, and the combination of a narcotic analgesic with atropine. Gastroscopy did not appear to increase plasma enzyme concentrations in six patients who were given intravenous premedication. The significance of these findings to the diagnosis of myocardial infarction is discussed.