Pharmacokinetics of ibuprofen in man. I. Free and total area/dose relationships

Ibuprofen kinetics were studied in 15 subjects after four oral doses. Plasma levels of both total and free ibuprofen were measured for 12 hr, and urine was collected for 48 hr after the doses. All subjects showed a nonlinear relationship between dose and total ibuprofen plasma AUC. Free ibuprofen plasma AUC, however, was linearly related to the dose, suggesting that oral clearance based on free drug was dose independent. Urinary recovery data indicated that efficiency of absorption was dose independent.