1-Octanol/Water Partition Coefficients of 5 Pharmaceuticals from Human Medical Care: Carbamazepine, Clofibric Acid, Diclofenac, Ibuprofen, and Propyphenazone

Laboratory studies were conducted to characterize the 1-octanol/water partition coefficients of pharmaceutically active substances carbamazepine, clofibric acid, diclofenac, ibuprofen, and propyphenazone. Partition coefficients determined by shake flask experiments (OECD guideline 107) varied between log K _OW 1.51 for carbamazepine, 2.88 for clofibric acid, 1.90 for diclofenac, 2.48 for ibuprofen, and 2.02 for propyphenazone. Comparison of these values with the literature values revealed rather significant differences for most of the compounds. The partitioning coefficients of the acidic compounds diclofenac and ibuprofen agreed much better with sorption and mobility data from previously conducted experiments, whereas K _OW values for carbamazepine were lower and for clofibric acid higher than expected from experiments. Only K _OW values for propyphenazone were in the same range as reported in the literature and expected from column experiments.