Effect of cephapirin on tubular reabsorption of amino acids, uric acid and beta 2‐microglobulin in man.

Abstract

Cephapirin, a beta‐lactam antibiotic, was administered intravenously to five healthy subjects in a dose of 1 g. Renal clearances of cephapirin, beta 2‐microglobulin, uric acid and amino acids were measured during the experiment and compared to timed control data, i.e. when no cephapirin was given. Renal clearance of cephapirin decreased when plasma concentrations declined. As protein binding of cephapirin is constant over a wide plasma concentration range, this finding may indicate that cephapirin is reabsorbed in the kidney by a saturable process. Renal clearance of endogenous amino acids, particularly those belonging to the basic group increased after cephapirin. There was no change in renal clearance of beta 2‐microglobulin which excludes a general toxic effect on tubular reabsorption of endogenous substances caused by cephapirin. A flow dependent increase of uric acid clearance was observed. Our results are suggestive of a competition between cephapirin and amino acids for some common step in the tubular reabsorption process.

Renal excretion of intravenously infused amoxycillin and ampicillin.

“…As the half-life is a function of clearance and volume of distribution, and these parameters could not be estimated from the terminal phase, the reason for the longer halflife cannot be determined. In contrast to previous findings with some other 3-lactam antibiotics, cephapirin and cephaloridine (Arvidsson et al, 1979(Arvidsson et al, , 1983, the renal clearance of amoxycillin and ampicillin appears to be independent of the plasma concentration. This indicates that the plasma concentrations were well below those required for saturation of tubular secretion, a prerequisite for the study.…”