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This study was conducted to investigate the possibility of performing nose-to-brain delivery of TS-002, which is an analog compound of prostaglandin D2 (PGD2) and thus would be a natural sleep inducer. The absolute bioavailability (BA) and sleep-inducing effect (SIE) following intranasal (IN) administration of TS-002 dry powder to cynomolgus monkeys were evaluated in comparison with intravenous (IV) administration. The SIE was evaluated as the accumulated time of sleeping-posture for 3 h. The brain distribution of TS-002 following IN administration of the dry powder was examined in rats. The absolute bioavailability (BA) in monkeys following IN administration of the dry powder (0.4-1.2 mg/body) was comparatively high (43.4-78.0%). The SIE following IN administration (0.05-0.4 mg/body) showed dose-dependency and its effect at 0.4 mg/body was twice as strong as that for IV administration (P < 0.05). The brain concentrations in rats following IN administration (0.1 mg/kg) were obviously higher than that for IV administration at the same dose. The highest content was observed in the olfactory bulb. These results demonstrated that TS-002 was directly transported from the olfactory region to brain, thereby showing that it may be possible to develop a novel sleep-inducing drug based on nose-to-brain delivery.

0 The effect of pulverization on the dehydration behavior of 2-[(2-methylimidazol-1-yl)methyl]benzo[f]thiochromen-1-one monohydrochloride hemihydrate (GK-128), a newly developed serotonin 3 receptor antagonist, was studied using powder X-ray diffraction analysis, thermogravimetry (TG), and differential scanning calorimetry (DSC). The crystalline forms of GK-128 obtained by pulverizing with a jet mill and an agate mortar were each confirmed to be the same as that of intact GK-128, since the powder X-ray diffraction patterns of the two prepared samples were identical with that of intact GK-128. However, after pulverization by jet mill, the dehydration temperature of GK-128 was markedly lowered and the DSC endothermic peak due to dehydration disappeared. The activation energy for dehydration, calculated by the Ozawa method using TG data, decreased with decreasing particle size and/or crystallinity of GK-128 crystals, e.g., the activation energies for dehydration of intact and jet-milled GK-128 were 128.1 and 75.9 kJ/mol, respectively. The results of comparison of powder X-ray diffraction patterns of pulverized GK-128 and intact GK-128 and of determination of the crystal structure of GK-128 suggested that water molecules could be removed easily along the c-axis of GK-128 crystals.

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