The Role of the Low Resistance Period in Determining the Effective Dosage of Chlortetracycline in Mice

Abstract

In various experimental infections inthe mouse, the single doses of chlortetracycline were determined which, when given simultaneously with the infection, prevent death of the animals. Serum concentrations of the antibiotic were measured in mice treated with 80–100% effective doses. During the initial period of infection, which is characterized by insufficient defence (low resistance period), these concentrations are invariably above or approximately equal to the minimum bacteriostatic concentration established in vitro. Hence, it is concluded that in animal experiments the dosage is dependent not only on the in vitro sensitivity of the infectious agent but also on the length of the LRP, during which the micro-organisms have to be controlled by a bacteriostatic agent.

The Serum Concentration of Bactericidal Antibiotics (Rifampicin, Cephaloridine) in Relation to the Low Resistance Period in Experimental Infections

“…Nevertheless, as with bacterio static substances [Sackmann, 1968[Sackmann, , 1971, a correlation between the effective dose, the sensitivity of the pathogen and the LRP is still evi of Bactericidal Antibiotics (Rifampicin, Cephaloridine) 209 dent. In infections with micro-organisms such as P. avicida and D. pneumoniae, in which the LRP is comparatively long, the effective dose in relation to the sensitivity of the pathogen is higher than in infections with E. coli, S. typhimurium and L. monocytogenes, for example, in which the LRP is short.…”