Penetration of Antimicrobial Agents into the Prostate

In the present review article, the penetration of antimicrobial agents into prostatic fluid and tissue was examined. Three major factors determining the diffusion and concentration of antimicrobial agents in prostatic fluid and tissue are the lipid solubility, dissociation constant (pKa) and protein binding. The normal pH of human prostatic fluid is 6.5-6.7, and it increases in chronic prostatitis, ranging from 7.0 to 8.3. A greater concentration of antimicrobial agents in the prostatic fluid occurs in the presence of a pH gradient across the membrane separating plasma from prostatic fluid. Of the available antimicrobial agents, beta-lactam drugs have a low pKa and poor lipid solubility, and thus penetrate poorly into prostatic fluid, expect for some cephalosporins, which achieve greater than or equal to the inhibitory concentration. Good to excellent penetration into prostatic fluid and tissue has been demonstrated with many antimicrobial agents, including tobramycin, netilmicin, tetracyclines, macrolides, quinolones, sulfonamides and nitrofurantoin.