[Hemostasis disturbance caused by cephalosporins with an N-methylthiotetrazole side chain. A randomized pilot study].

The mechanism of hypoprothrombinemia induced by cephalosporins containing the N-methylthiotetrazole (NMTT) side chain has been investigated in a randomized clinical, trial (pilot study) with 14 hospitalized patients (main inclusion criteria: age greater than or equal to 50 years, urinary tract infection, normal prothrombin time. Therapy groups: latamoxef (n = 5), cefoperazone (n = 5), cefotaxime (control, n = 4). Duration of treatment: 7 days). Two patients under cefoperazone exhibited a significant increase of prothrombin time, accompanied by the appearance of PIVKA II (prothrombin induced in vitamin K absence). Both cefoperazone (in 4 patients) and latamoxef (in 3 patients) caused the appearance of endogenous vitamin K1 2,3-epoxide, whereas cefotaxime did not. This confirms the hypothesis that NMTT-cephalosporins are inhibitors of hepatic vitamin K epoxide reductase, and that this is at least partly responsible for the clinically observed hypoprothrombinemia. In older patients treated with these antibiotics, prothrombin time should be controlled before as well as under therapy. Unexpectedly, the patients displaying an appearance of vitamin K1 2,3-epoxide showed a statistically significant increase of endogenous plasma vitamin K levels. This effect needs further investigation.