Pharmacokinetics of phenoxymethylpenicillin in volunteers.

Pharmacokinetics of phenoxymethylpenicillin was studied in 12 healthy volunteers. They received four different single oral dose sizes. At all dose levels (0.4, 1, 2 and 3 g) phenoxymethylpenicillin was rapidly absorbed, usually with serum peaks within 0.75 h. The mean maximal serum peaks (+/- SD) were 6.1 +/- 2.0, 15.0 +/- 4.3, 26.3 +/- 10.0 and 35.5 +/- 10.8 mg/l after 0.4, 1, 2 and 3 g, respectively. The relationship between the mean peak serum concentrations and the doses was nonlinear (p less than 0.001). The mean areas under the serum concentrations vs. time curve (AUC) increased almost linearly with increasing doses, and the deviation from linearity was not significant (p less than 0.05). Very low penicillin concentrations were obtained in saliva. The urinary excretion during 10 h was 37--43% of the doses given. The pharmacokinetic results indicated that phenoxymethyl penicillin in the present formulation is rapidly and well absorbed up to as high doses as 3 g. The tablet formulations used were better absorbed than previous ones. The percent of absorption was relatively lower with the highest doses, but this probably has only minor therapeutic consequences.