[Semisynthetic penicillins and cephalosporins inhibit in vitro myelopoiesis in a dose-dependent manner].

Penicillin-G degradation products have been shown to inhibit in vitro myelopoiesis in a dose-dependent manner. Similar inhibition was seen with 6 semisynthetic penicillins and 2 cephalosporins. 50% inhibitory doses in vitro well matched total and daily doses given in vivo before neutropenia developed. These findings suggest a toxic rather than an immune-mediated pathogenesis for betalactam-induced neutropenia.