An in vitro pharmacodynamic model to simulate antibiotic behavior of acute otitis media with effusion

The purpose of this investigation was to develop an in vitro pharmacodynamic model (IVPM) that would simultaneously simulate in vivo serum and middle ear amoxicillin pharmacokinetic characteristics of acute (purulent) otitis media and then utilize the IVPM to assess amoxicillin-mediated killing of a type 7F Streptococcus pneumoniae (MIC = 0.002 mg/L). The IVPM consisted of a sterile central compartment and a membrane-bound "infected" peripheral compartment. Peak peripheral compartment amoxicillin concentrations occurred within 2 hr after its introduction into the central compartment and were approximately 30% of peak central compartment concentrations. Amoxicillin elimination from the central compartment was designed to provide a 1-hr t 1/2. Amoxicillin elimination from the peripheral compartment was slower than from the central compartment, with an average half-life of 2.3 hr. Significant concentration-related differences in maximal bacterial kill rates were not detected over the range of amoxicillin concentrations studied (0.26 to 14.6 mg/L). However, at peak central compartment amoxicillin concentrations of less than or equal to 2 mg/L, a lag phase in killing was observed. In general, the in vitro pharmacokinetic data derived from this model compare well with published in vivo data.