Stereoselective drug release from ketoprofen and ricobendazole matrix tablets

Crystalline characteristics of racemic, pure R and S enantiomers and physical mixtures of Ketoprofen (KET) have been studied by DSC and X-ray diffractometry. Aqueous solubilities were 182.6 +/- 9.1 microg/ml for racemic KET, 259.6 +/- 6.6 microg/ml for R-KET, and 304.3 +/- 2.7 microg/ml for S-KET. Matrix tablets made with racemic and physical mixtures of KET show stereoselective drug release, which is faster for S-KET than for R-KET. This effect is more marked when the chiral excipient hydroxypropylmethylcellulose (HPMC) is used in place of the achiral Eudragit RL. Stereoselectivity of release is also affected by the amount of KET. Similar results were obtained when another chiral drug with low solubility, Ricobendazole (RBZ), is used. Depending on the excipient and drug dosage, more or less marked stereoselective drug release is obtained in RBZ matrix tablet formulations.