Cefotaxime metabolism by hemolyzed blood: quantitation and inhibition of the deacetylation reaction.

The metabolism of cefotaxime (CTX) by hemolyzed blood at different concentrations, time intervals, and temperatures was studied. Cefotaxime and desacetylcefotaxime (DES) levels were quantitated by reverse phase high pressure liquid chromatography. When CTX was added to tubes with 10% hemolysis, CTX/DES levels (micrograms per milliliter) were 123/134, 161/114, and 202/60 at 37 degrees C, room temperature, and 4 degrees C, respectively, after a 1 hr incubation. No reduction in CTX was observed in control experiments (10% blood, no hemolysis) at these temperatures after 1 hr; 200 +/- 23 micrograms/ml CTX; 5 +/- 2 micrograms/ml DES. The disappearance half-life of CTX in 10% hemolyzed blood at 37 degrees C was 45.7 min and at room temperature 84.3 min (p less than 0.001). The addition of the enzyme inhibitors ethylenediaminetetraacetic acid and p-hydroxymercuibenzoate reduced the metabolism of CTX in the presence of 10% hemolysis after 1 hr at 37 degrees C from 41% to 19% with ethylenediaminetetraacetic acid (0.45 mM) and to 0% with p-hydroxymercuibenzoate (10 mM). Our results suggest that for accurate determinations of CTX serum levels, which often have some degree of hemolysis, such specimens should be collected in tubes with ethylenediaminetetraacetic acid or p-hydroxymercuibenzoate and transported at 4 degrees C.