PHARMACOKINETICS OF PENICILLIN ANTIBIOTICS: INTRAVENOUS-TO-ORAL SWITCH THERAPY

Penicillin antibiotics are time-dependent bactericidal agents. Most of them have very short elimination half-life. As regards their bioavailability, benzylpenicillins are not absorbed following oral administration, while oral ampicillin and cloxacilin are poorly absorbed, and amoxicillin is almost completely absorbed. These drugs are suited for intravenous to oral switch provided that plasma concentrations after oral administration are comparable to those following intravenous application. The assessment is made by calculating the average steady-state plasma concentration. Consequently, the same bactericidal activity can be expected. Oral therapy has many advantages over intravenous administration, including lower treatment costs, shorter hospital stay, lower incidence of phlebitis and sepsis, and greater patient convenience. However, switch therapy is not possible in critically-ill patients, and in patients with fever, increased inflammatory parameters, or malabsorption syndrome. This paper presents two cases of intravenous to oral antibiotic switch therapy. On the basis of pharmacokinetic simulations and evaluation of the efficacy of antibacterial treatment, oral amoxicillin therapy was found to be comparable to intravenous amplicillin treatment; the suitability of switching intravenous to oral cloxacillin for the treatment of osteomyelitis remains unascertained. Based on appropriate interpretation of pharmacokinetic parameters, intravenous to oral antibiotic switch therapy has proved to be an effective and safe pharmacotherapy for bacterial infections.