Erythromycin ethyl succinate: diffusion through interstitial dermal fluid.

Erythromycin is widely used in dermatology. There are few studies of its diffusion in the skin. The diffusion of erythromycin ethyl succinate (EES) in dermal fluid has now been investigated by the suction blister method. Suction blister fluid (SBF) and blood samples were collected from 10 volunteers before administration of 1 g EES and 10 times during the following 24 h. The median peak serum level was 2.05 micrograms/ml and in SBF it was 0.34 microgram/ml. The median ratio of the areas under curves (f SBF/f serum) was 43%. In all subjects EES concentrations in SBF between the second and twelfth hours exceeded 0.1 g/ml. The results show good diffusion of EES through normal skin from the second to the twelfth hours after oral administration.