Biorelevant in vitro dissolution coupled with n-octanol partition assay to predict in vivo absorption of ketoprofen after oral administration

The purpose of this study is to predict in vivo oral absorption of ketoprofen in fasting conditions. In vitro dissolutions for an immediate-plus-extended-release bilayer tablet [Bi-Ketofen®, Roemmers (Uruguay)] were performed with USP IV apparatus. Experimental conditions simulated ketoprofen’s gastrointestinal release in both sexes, considering women’s lower contractile strength and longer gastric emptying. Dissolution media-to-n-octanol distribution was then estimated. Data from a previously published in vivo study was used as correlator. Once the immediate-release layer was dissolved, dissolution rates became slower and similar for men and women, reaching practically the same percentage of dissolution. However, because of the higher intestinal pH of women, ketoprofen partitioned into n-octanol was lower than in men. In conclusion, good correlation between the percentage of dose extracted by n-octanol and the percentage of dose absorbed in both sexes was found. Women may not allow the complete absorption of acidic drugs such as ketoprofen, especially for extended-release formulations.