THUS FAR, it has been assumed that successful penicillin therapy of susceptible surgical infections depended primarily on the maintenance of a therapeutic concentration of this agent in the blood and tissues. A concentration of 0.03 unit per cubic centimeter has usually been recognized as a therapeutic level. The origin of this concept was probably the result of a transfer of experimental and clinical experience with the sulfonamide drugs.
At the time of its introduction to clinical surgery, penicillin was given by continuous infusion, either intravenously or intramuscularly, in the majority of instances. Because of the patient's discomfort and the amount of time and effort needed to insure its efficiency, this method was soon abandoned in favor of single injections made at intervals of two to four hours. Although this plan did not maintain a constant level, it insured a concentration of penicillin in excess of the therapeutic dose in most