Cefatrizine

Objective: To investigate the effect of gestation on the pharmacokinetics of orally administered beta-lactams, choosing cefatrizine as the model antibiotic. Setting: A tertiary teaching hospital. Design: Prospective study. Methods: In 20 women with affected fetuses, 17 by beta-thalassemia major and 3 with congenital malformations, termination of gestation between 19 and 24 weeks was induced by intra-amniotic administration of prostaglandin F(2)(alpha). Pharmacokinetics of cefatrizine in maternal and fetal blood were studied after the administration of three 1 g doses of oral cefatrizine, every 12 h. Twenty female non-pregnant volunteers consisted the control group. Results: Gestation was found to decrease substantially both cefatrizine oral bioavailability and maximum serum plasma concentration (42.8 and 44.5%, respectively) but increased elimination half-life. This effect can be attributed to a substantial increase of the apparent volume of distribution of cefatrizine in relation to a moderate increase of clearance that occurs during pregnancy. Fetal serum cefatrizine levels were lower for the first few hours after administration and then exceeded the corresponding maternal ones. Conclusions: Our results indicate that gestation decreases the oral bioavailability of cefatrizine. A delay in the maternal drug elimination compared to non-pregnant controls was more pronounced in the fetus.

A rapid and specific high-performance liquid chromatographic method was developed and validated for the simultaneous determination of cefatrizine and clavulanic acid in the plasma of beagle dog. The sample pretreatment procedure involved reaction of clavulanic acid with 1,2,4-triazole, which readily produced a derivative with its maximum UV absorption at 314 nm. This derivative was separated in a reverse-phase C-18 column without being interfered by other components present in plasma. Cefatrizine, however, was not derivatized and, therefore determined directly at 269 nm. Sulfanilamide was used as an internal standard. The retention times of sulfanilamide, the derivative, and cefatrizine were, 3.5, 4.9, and 6.0 min, respectively. The assay showed linearity from 2 to 100 microg/ml for cefatrizine and from 1 to 50 microg/ml for clavulanic acid. Precision expressed as R.S.D. ranged from 4.2 to 18.2% for cefatrizine and 5.5 to 15.8% for clavulanic acid. Accuracy ranged from 97.9 to 120% (lower limit of quantitation) for cefatrizine and from 97.7 to 119.2% for clavulanic acid. Extraction efficiencies for cefatrizine, clavulanic acid, and internal standard from dog plasma averaged 79.8+/-5.8%, 84.8+/-6.2%, and 89.0+/-3.8%, respectively. This method was employed successfully to follow the time course of the concentration of cefatrizine and clavulanic acid in beagle dogs following oral administration of cefatrizine and clavulanic acid.

The arrival of new cephalosporins faces the clinician with an evergrowing confusion as to the drug of choice. The older agents (cephalexin, cephradine, cefadroxil and cefaclor) and the newer formulations cefatrizine and cefuroxime axetil are intensively used for treatment of mild and moderate infections. The oldest agents have a better pharmacokinetic profile but are less active against Gram-positives and Gram-negatives. Cefaclor, cefatrizine and cefuroxime axetil have improved in vitro activity against H. influenzae and/or against S. aureus and M. catarrhalis. However the mean free serum concentrations after proposed standard daily doses of cefaclor (3 x 250 mg/d), cefatrizine (2 x 500 mg/d) and cefuroxime-axetil (2 x 250 mg/d) are lower than those of the older cephalosporins. In comparison amoxicillin-clavulanate is equally efficacious, has a more reliable pharmacokinetic profile and is less expensive than cefaclor and cefuroxime axetil in a comparable dose (e.g. 3 x 500 mg/d).