Pharmacokinetics and endometrial and tubal tissue penetration of cefalotin and cefazolin

The pharmacokinetics and concentrations of the two antibiotics cefazolin and cefalotin were studied during gynecologic operations in endometrial and tubal tissue. The patients received 0.05 g/kg of the antibiotics by intravenous injection. Under the given conditions, pharmacokinetic calculation of the plasma elimination gave half-lives of 24.8 min for cefalotin and of 63 min for cefazolin. Fitting of the tissue levels to the Bateman function showed that the two antibiotics diffuse rapidly into both tubal and endometrial tissue and attain peak concentration levels between 10 and 25 min. In both tissues the concentrations of cefazolin were higher than those of cefalotin. Higher tissue concentrations of cefazolin could also be demonstrated in experiments of longer duration.