Monitoring of serum concentrations of antibiotics by microbiological method: a one-year experience.

By monitoring serum concentrations of antibiotics one may have an opportunity to make optimal adjustment of dosing regime for each individual patient, resulting in therapeutic concentrations in tissues and avoiding their cumulation and thus side effects in the organism. Concentrations of gentamicin, amikacin, streptomycin, ceftriaxone, benzylpenicillin, clindamycin and lincomycin were measured in serum of 110 patients by microbiological agar cup method. The measurements were made only after establishment of steady-state. Current dosing regime of gentamicin gave systematically subtherapeutic serum concentrations, while usual doses of amikacin and streptomycin achieved serum concentrations slightly lower than minimal toxic concentrations. Three patients actually had toxic serum concentrations of amikacin. Current dosing regime of penicillin produces therapeutic serum concentrations. The results of our study recommend monitoring of serum concentrations of antibiotics by a microbiological method in patients not responding to antibiotic therapy or having insufficiency of excretory organs.