Concentrations of phenoxymethylpenicillin and cefadroxil in tonsillar tissue and tonsillar surface fluid.

Thirty patients who underwent elective tonsillectomy were given phenoxymethylpenicillin (0.8 g) or cefadroxil (1 g) at different times before operation. The concentrations of the antibiotics were analysed in serum, tonsillar tissue, fluid from the surface of the tonsils, and mixed saliva. The concentrations in tonsillar tissue for both drugs were much lower than the corresponding serum concentrations. This apparently low tissue accessibility could be ascribed to the limited intracellular penetration of beta-lactam antibiotics. For both antibiotics the concentrations in the tonsillar surface fluid were higher than the levels in the tissue and well above the minimal inhibitory concentrations for streptococci. This was not due to antibiotics in saliva but probably a result of leakage from the interstitial fluid. Inability to reach active concentrations of phenoxymethylpenicillin or cefadroxil at the site of infection does not therefore seem to be a probable cause for relapse after treatment of streptococcal tonsillitis.