Cephalosporin-induced hypoprothrombinemia: is the N-methylthiotetrazole side chain the culprit?

The reported high incidence of vitamin-K-reversible hypoprothrombinemia associated with the new beta-lactamase-stable cephalosporins prompted us to evaluate the effect on hemostasis of three cephalosporins (cefamandole, ceftriaxone, and ceftazidime) in 30 patients with serious infections. Cefamandole and ceftriaxone, both containing a sulfhydryl group, induced a significant and similar prolongation of prothrombin time and decrease in factor VII activity. Ceftazidime, in contrast, had no effect on these two parameters.