[The plasma-protein-binding of Clindamycin Cephazolin and Cephradin in neonates and adults (author's transl)].

In pooled serum of 12 healthy adults and 12 neonates (blood taken from the umbilical cord) the free and protein-bound parts of Cephazolin, Cephradin and Clindamycin were tested by equilibrium dialysis in relation to the concentration of the antibiotic. In the serum of adults at a concentration of 36 mcg/ml the free part of Cephazolin amounted to 16%, at a concentration of 35 mcg/ml the free Cephradin was 87%, at a concentration of 97 mcg/ml the free Clindamycin was 16%. The binding constant k of Cephazolin was 12.0 (rise-constant 0.58), of Cephradin 0.26 and of Clindamycin 15.8 (rise-constant 0.58). When concentration of antibiotics rose, the free part of Clindamycin and Cephazolin increased more than with Cephradin. At a concentration of 30--42 mcg/ml the differences between the sera of adults and neonates were 26.4% with Cephazolin, 3.7% with Cephradin and 3.1% with Clindamycin (concentration 92--97 mcg/ml). In neonates the free part of Cephazolin was 43%, of Clindamycin 19% and of Cephradin 90%. The lower ablumin content in serum of neonates (3.7 g%) does not altogether explain the reduced protein-binding. In neonates a different affinity for binding has to be assumed.