Comparative effects of cefoxitin and cefotetan on vitamin K metabolism.

The effects of cefoxitin and cefotetan on vitamin K metabolism and clotting parameters in five healthy subjects were investigated. No changes in prothrombin time or in the formation of abnormal prothrombin were seen either during or following the cefoxitin or cefotetan phase. However, when phytonadione (10 mg) (vitamin K1) was administered at the completion of each course of antibiotics, formation of vitamin K 2,3-epoxide was observed only during the cefotetan phase. It is probable, therefore, that cefotetan, a cephamycin antibiotic containing the N-methylthiotetrazole side chain, inhibits hepatic vitamin K 2,3-epoxide reductase. While hypoprothrombinemia and formation of abnormal prothrombin were not seen in healthy subjects, the effect of cefotetan on the coagulation status of vitamin K-depleted patients may be adverse.