The inclusion of fluoxetine into γ-cyclodextrin increases its bioavailability: behavioural, electrophysiological and pharmacokinetic studies

Abstract.

The inclusion of a drug into cyclodextrin generally results in the modification of its physical and chemical properties and sometimes can increase its oral bioavailability. The aim of this study was to compare the effects of the fluoxetine HCl/γ-cyclodextrin complex to that of traditional fluoxetine HCl. In the forced swimming test in mice, fluoxetine HCl/γ-cyclodextrin was more effective than fluoxetine HCl, the ED₃₀s being, respectively, 9.5 and 16.9 mg/kg PO. Both compounds (10 mg/kg PO) were able to reduce the firing rate of dorsal raphe neurons in the rat. However, between-groups comparisons showed no significant differences between fluoxetine HCl treated animals and the vehicle group, while fluoxetine HCl/γ-cyclodextrin appeared significantly more effective than vehicle from minute 25 of the measurement period. In healthy volunteers, the relative oral bioavailability, calculated as the ratio AUC 0-∞ fluoxetine HCl/γ-cyclodextrin on AUC 0-∞ fluoxetine HCl (20 mg PO), was equal to 249.9%. The three experiments taken together suggest that the complexation of fluoxetine HCl into γ-cyclodextrin increases its pharmacological efficacy in animals, this effect being related to an enhancement of its oral bioavailability as demonstrated in human healthy subjects.