[Depoteffect of benzathine-penicillin (author's transl)]

15 test persons received an injection of 2,400,000 units of benzathine penicillin. Serum levels were subsequently assayed, as well as the excretion of the antibiotic in the urine. The samples were stored in liquid-nitrogen between collection and examination. Each of the speciemens was tested 5 to 10 times and the results were ascertained by empirical evaluation of every single analysis. This assay showed the existence of mean levels above 0.036 I.U./ml in the serum and above 19.75 I.U./ml in the urine for the duration of 26 days. The evaluation of serum levels after the administration of antibiotics is difficult due to several sources of error. Reliable results can, therefore, be obtained only by examination at special institutes which possess experienced technical personnel. The establishment of reference laboratories for this purpose is suggested. The results of the study confirm the efficacy of one-shot treatment of the syphilis by administration of 2,400,000 to units of benzathine penicillin.