How bio-relevant buffering media affect dissolution and release kinetics of solid formula: Ibuprofen as a model

The mechanism of buffer species on the in vitro breakdown and dissolution behaviors and the release mechanism for solid formula has been revealed. The ibuprofen sustained-release capsules and tablets were employed as they are well known drugs and one of the most often used drug too. The results showed that the dissolution of the capsules was faster in medium A (with phosphate as the main buffer system) with a shorter half-disintegration time t1/2 (175.0 min) compared to that in medium B using bicarbonate as the buffer (211.7 min). The tablets exhibited intact morphology and structure in both dissolution media, whereas a shorter t1/2 (606.3 min vs. 694.9 min) along with a higher dissolution ratio (78.3% vs. 52.7%) were shown in medium B. These correspond to the microstructural analyses where the tablets collected from medium B presented a more uneven and rougher surface with more cracks during dissolution. As revealed by the release kinetics, the dissolution medium seems to have little influence on the release mode of ibuprofen capsule and tablet formulations. The release of ibuprofen was mainly dominated by erosion. This study provides quantitative information regarding the buffering effect. Such knowledge is important for future selection and optimization of buffer species that corresponds to the dosage type.