Serum penicillin concentrations and urine excretion rates of oral benzathine penicillin G and phenoxymethyl penicillin potassium were evaluated in children. Mean peak serum concentration of 0.134 microgram/ml of benzathine penicillin G and 1.018 microgram/ml of phenoxymethyl penicillin potassium were measured at 125 and 35 min. The mean half-life times were 1.36 and 0.74 hr, and for area under the curve, the values were 0.34 and 1.68 microgram . hr/ml for benzathine penicillin G and phenoxymethyl penicillin potassium groups, respectively. Phenoxymethyl penicillin potassium had more reliable pharmacokinetic properties and would be the preferred forms of oral penicillin. However, all patients receiving penicillin G had penicillinemia, which was enough to inhibit most strains of Streptococcus pyogenes for a longer period than phenoxymethyl penicillin potassium. Palatability of phenoxymethyl penicillin is less than for benzathine penicillin G; the latter may be used for children in whom compliance may be a problem.
