A new ibuprofen transdermal nanosystem, designed by using an ethosomal carrier, was characterized and tested for its pharmacokinetic profile and therapeutic effects in animal models. It was found that the ethosomal nanosystem contains unilamellar vesicles with a normal size distribution of about 200 nm. The drug applied transdermally from the ethosomal gel was present in plasma for a longer period of time as compared to the oral administration and showed a high relative bioavailability. Ibuprofen plasma concentration reached a Cmax of 74.11 +/- 18.52 microg/ml 2 hours post application on rat skin. The ibuprofen ethosomal gel had an efficient antipyretic effect in fevered rats. Animal body temperature decreased to normal value gradually with duration of action of at least 12 hours compared to only 7 hours after the oral treatment. The transdermal ibuprofen gel also induced an analgesic effect 30 minutes following its application lasting for at least 6 hours. Biochemical and clinical hematological analysis results of the blood taken from animals in all experimental groups and those of skin histological examination show that ibuprofen ethosomal gel is safe and does not irritate the skin. Data obtained in this work suggest that the designed ethosomal ibuprofen gel could be further investigated in humans for its antipyretic effect.