This investigation was aimed at the improvement of the bioavailability of cinnarizine (CN) by administering its β-cyclodextrin (β-CD) complex together with a competing agent. The ability of L-leucine (L-Leu) and L-isoleucine (L-Ileu) to act as competing agents was evaluated by determining the penetration rate of CN, employing a Sartorius absorption simulator. L-Ileu showed a stronger competing action than L-Leu. The bioavailability of CN, upon oral administration of the CN-β-CD inclusion complex, was enhanced by the simultaneous administration of L-Ileu as a competing agent; C_max was 1.9 and 2.7 times those of CN-β-CD complex alone and CN alone, respectively. L-Leu showed no clear effect on the bioavailability. The in vivo competing effects of L-Leu and L-Ileu appeared to be in agreement with the in vitro evaluations.