404 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1952 



application. The number of cases of contact dermatitis following 

 topical application of penicillin makes one question the value of this 

 drug for local therapy. In addition to contact dermatitis, an Arthus 

 type of reaction and a condition resembling serum sickness are en- 

 countered. Keactions are seen most frequently after topical applica- 

 tion of the drug but similar reactions have occurred following 

 parenteral administration after initial topical use, and after parenteral 

 or oral administration only. In some instances, reactions occur after 

 initial exposure and in others after subsequent administration. In 

 any case, the increase in frequency of reactions observed following 

 penicillin therapy indicates that local application of the drug should 

 be used with considerable caution. In addition, since bacitracin is as 

 effective topically as penicillin, consideration should be given to its 

 use because of its low incidence of sensitization following application. 



Absorption and excretion. — When penicillin is injected intraven- 

 ously, concentration in the blood reaches a "peak" almost immediately. 

 The concentration in the blood decreases rapidly and after a few 

 hours little, if any, can be detected by assay, although it may be de- 

 tected in the urine for a longer period of time. The peak concentration 

 of penicillin following intravenous injection as well as the duration 

 of blood concentrations depends on the quantity of the drug adminis- 

 tered. Since the first clinical trials were made in this country, it has 

 been customary to consider that a maintained plasma concentration of 

 0.03 unit per ml. or better is satisfactory for most penicillin-susceptible 

 infections other than the most severe. This is an arbitrary figure and 

 it was chosen primarily because of limitations of the bioassay method 

 utilized for determining blood concentrations of penicillin in man. 

 Obviously, some bacterial strains are inhibited by lower concentrations 

 of the drug while others require considerably higher ones to obtain 

 the desired therapeutic result. Practically all the clinical evidence 

 available on penicillin is based on a maintained plasma penicillin 

 concentration and for general use this appears to be the most satisfac- 

 tory procedure. There is, however, both laboratory and clinical evi- 

 dence that a continuous plasma concentration is not essential for good 

 therapeutic results. 



After intramuscular injection, the highest penicillin concentration 

 in the blood is reached usually within one-half hour with a slower 

 fall than seen following intravenous administration. The peak con- 

 centration of penicillin in the blood is not so high as would occur 

 with the same dose given intravenously. For intramuscular injection, 

 the intermittent method is most generally used although under certain 

 exceptional circumstances the drug is given by continuous intramus- 

 cular infusion. Subcutaneous injection is apt to be painful, and 

 absorption is slow and uncertain. It has been shown that radioactive 



