Intrasubject variability in bioequivalence studies illustrated by the example of ibuprofen

Based upon the results of a bioequivalence study in 18 male and female healthy volunteers receiving each ibuprofen 400 mg at a time interval of 3 days the issue of the intrasubject variation is discussed. It was shown that there was bioequivalence as to the parameters Cmax, AUC0-tlast und AUC0-infinity in the volunteers who repeatedly received the same preparation. The same is true for the secondary target parameters tmax und t1/2. In the present study the intrasubject variability was determined to be 10%. Since ibuprofen does not belong to the drugs with problematic bioavailability it can be expected that in case of repeated application at an interval limited in time equal results are achieved with considerable intra-and intersubject variations.