Pharmacokinetics of phenoxymethylpenicillin in tonsils

The pharmacokinetics of phenoxymethylpenicillin in tonsillar tissue was studied in 33 patients who underwent tonsillectomy, mainly because of repeated tonsillitis or peritonsillitis. The patients were operated on 30-240 min after an oral penicillin dose of 12.5 mg/kg body weight. The mean serum concentration was 2.8 micrograms/ml for 10 patients operated upon 80-95 min after drug administration. The mean tissue concentration for these patients at the same time was 0.6 micrograms/g. The mean concentration of penicillin in tissue after 240 min was 0.05 micrograms/g. 19% of the serum concentration was recovered in the tonsillar tissue. No significant difference between penicillin concentration in the centre or surface of the tonsils was found. The tissue concentration was calculated to be above 0.03 micrograms/ml for at least 4-5 h. 30% of the patients harboured penicillinase producing bacteria on their tonsils, mainly Staphylococcus aureus. These patients had a lower tissue concentration than those lacking the bacteria, but the difference was not statistically significant (p = 0.095).