Penicillanic acid derivatives in the canine prostate

Distribution of ampicillin, amoxicillin, bacampicillin, mecillinam, pivmecillinam, carbenicillin, indanyl sodium was studied in the canine prostate, prostatic interstitial fluid, and prostatic secretion. All seven antibiotics were found in higher concentrations in the prostatic interstitial fluid than in the prostatic secretion. As expected for weak acids, drug concentrations in these fluids were always lower than the simultaneous serum concentrations. Tissue penetration was enhanced for the penicillin ester, pivmecillinam, as shown by its prostatic secretion/serum and tissue/serum ratios, which were higher than those of the other antibiotics, including the esters, bacampicillin, and carbenicillin indanyl sodium. This results may be due to pivmecillinam's long hydrolysis half-life. The concentrations for these penicillanic acid derivatives in prostatic interstitial fluid were above the minimal inhibitory concentrations for most of the commonly encountered gram-negative bacteria encountered in prostatitis. Therefore, these antibiotics should be effective in the treatment of bacterial prostatitis caused by susceptible organisms. Carbenicillin and carbenicillin indanyl sodium had the highest prostatic interstitial fluid/serum ratios of the compounds tested, and theoretically, therefore, they should be the most effective in the treatment of prostatitis. However, clinical trials should be carried out to confirm this.