Penetration of Antibiotics into Fibrin Loci in Vivo. I. Comparison of Penetration of Ampicillin into Fibrin Clots, Abscesses, and "Interstitial Fluid"

Abstract

Fibrin clots were studied in vitro to determine the kinetics of entry and exit of two penicillins. The nature of the ambient bath did not affect the behavior of ampicillin. In contrast, oxacillin penetrated more slowly from serum than from Krebs-Ringer solution, and its exit from clots previously exposed to serum was similarly delayed. These phenomena may be related to protein binding of the drugs. Ampicillin was administered to rabbits by iv bolus, after which concentrations of the drug in various sites were measured. Levels in sc-implanted fibrin clots closely resembled those in abscesses, rising to a peak at 1 hr and thereafter remaining in excess of concentrations in serum. Levels approaching those in serum were rapidly achieved in “interstitial fluid” and declined at a slightly lower rate. These studies suggest that the model in the in vivo fibrin clot may provide an accurate representation of the behavior of antibiotics in a localized area of suppuration.