Cefpodoxime proxetil in upper respiratory tract infections

[Blood and respiratory diffusion of antibiotics. A critical analysis of predictive parameters for clinical effectiveness]

The implementation of a treatment for lower respiratory tract infections must integrate a pharmacokinetic/pharmacodynamic (PK-PD) approach of antibiotic dosing. The activity of beta-lactam antibiotics is best predicted by the duration of time during which serum concentrations exceed the MIC (T>MIC). T>MIC of 30-40% is sufficient to achieve clinical cure in immunocompetent patients. This threshold is achieved with amoxicillin for penicillin susceptible or resistant Sreptococcus pneumoniae and with amoxicillin-clavulanate and ceftriaxone for S. pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. For macrolides, the activity is best predicted by T>MIC and for azithromycin and telithromycin by area-under-the-curve/MIC (AUC/MIC). Sufficient PK-PD values are only achieved for macrolides against susceptible strains of S. pneumoniae and against M. catarrhalis; for telithromycin, an AUC/MIC>25, which is necessary for bacterial eradication, is achieved in>99% of patients for S. pneumoniae and M. catarrhalis and>90% of patients for H. influenzae. For fluoroquinolones, both peak/MIC and AUC/MIC are predictors of clinical and bacteriological efficacy. AUC/MIC required ratios vary according to pathogens and severity of diseases from 48 to 125. These thresholds are reached for respiratory pathogens; for S. pneumoniae, AUC/MIC90 ratios of levofloxacin and moxifloxacin are 96 and 192, respectively; the presence of a mutation in parC increases the risk for the acquisition of additional mutations and failure.

Activity of once-daily cefpodoxime regimens against Haemophilus influenzae and Streptococcus pneumoniae with an in vitro pharmacodynamic chamber model

To characterize the in vitro effectiveness of once-daily dosing with cefpodoxime against Haemophilus influenzae and Streptococcus pneumoniae infections, an in vitro pharmacodynamic chamber model was used to compare the bacterial killing activities of three cefpodoxime regimens: 100 mg twice daily (BID), 200 mg once daily (QD), and 400 mg QD. At the end of 24 h, the regrowth of H. influenzae isolates in the QD regimens was of concern, and the total logarithmic reduction was greatest in the BID regimen (3.1 log). Against S. pneumoniae isolates, the largest reductions in bacterial counts were observed in the 100-mg BID (5.5 log) and 400-mg QD (4.0 log) regimens. These data suggest that 400 mg of cefpodoxime given QD may have a role in the therapy of infections involving S. pneumoniae isolates.

Pharmacokinetics of cefpodoxime proxetil in healthy young and elderly volunteers

The influence of age on the pharmacokinetics of cefpodoxime was evaluated in 12 elderly (ages 65-85 years) and 12 weight- and sex-matched young (ages 20-33 years) subjects, each of whom received two cefpodoxime proxetil 200-mg tablets every 12 hours for 14.5 days. Serial blood samples and urine were collected after the first dose on day 1, after the morning dose on day 8, and after the last (morning) dose on day 15. Plasma and urine samples were assayed for cefpodoxime concentrations using HPLC methods. Within each age group, mean pharmacokinetic parameters determined on day 1 were similar to corresponding values on days 8 and 15, indicating that cefpodoxime does not accumulate after twice-daily dosing of cefpodoxime proxetil. Based on this result, parameters were pooled across days in each age group. No significant differences were observed between healthy and elderly volunteers in area under the plasma concentration-time curve for the 12-hour dosing interval, peak plasma concentration, or time to peak concentration. Mean urinary excretion and renal clearance of cefpodoxime were significantly lower in elderly subjects. Differences in renal clearance were attributed to the corresponding age-related reduction that was noted in creatinine clearance values, whereas the lower urinary excretion of cefpodoxime probably reflected slightly reduced systemic drug absorption in the elderly. Differences in these parameters between groups were less than 30%, and were unlikely to be of clinical importance. The data indicate that dose adjustment of cefpodoxime in elderly subjects having normal (age-adjusted) creatinine clearance values is not required.