Effect of low-molecular casein and gelatin on absorption of ibuprofen after oral and rectal administration.

Kneaded mixture of ibuprofen with low-molecular gelatin or casein (LM gelatin or LM casein) was prepared, and their in vitro dissolution, release from suppository base and in vivo absorption behaviours were examined. The dissolution rate of ibuprofen from the kneaded mixtures was markedly higher than that of the drug itself. The LM gelatin and LM casein also enhanced the release rate of ibuprofen from suppository base. After oral administration of the kneaded mixture with LM gelatin to beagle dogs, the initial serum concentration was higher than that of the drug alone. On the other hand, LM casein accelerated the absorption of ibuprofen from rectum. However, LM gelatin and LM casein did not affect the bioinversion of R(-)- to S(+)-ibuprofen.