Improving Bioavailability of Naftopidil in Dogs by Using Bioadhesion

To improve the bioavailability of naftopidil, bioadhesive sustained-release capsules and non-bioadhesive capsules were prepared. Bioadhesive polymers such as hydroxypropyl methylcellulose (HPMC) andCarbopol 934 (CP 934) were used in the bioadhesive capsules formulations. Naftopidil capsule and two formulationsof bioadhesive sustained-release capsules (I and II) were respectively given to five healthy male dogs in an openrandomized cross-over test. The naftopidil concentrations in plasma were determined by a newly developed HPLCmethod. The pharmacokinetic parameters and the relative bioavailability were measured. The AUC0→24, Cmax and Tmaxof non-bioadhesive naftopidil capsules were 3494.7±466.47 h@ng@mL-1, 697.48±94.22 ng@mL-1 and 1.15±0.49 h. Thesepharmacokinetic parameters of bioadhesive sustained-release capsules I and II were 4618.46±316.68 h@ng@ mL-1 and4746.44±317.22 h@ng@mL-1, 468.59±61.25 ng@mL-1 and 512.00±72.29 ng@mL-1, both 4.0±0.71 h respectively. Resultsfrom statistical analysis showed that there were significant differences between the two bioadhesive formulations andthe non-bioadhesive one in AUC0→24, Cmax and Tnax @ The relative bioavailability of the two bioadhesive sustained-release capsules were respectively 133.40±12.72% and 137.53±17.49% when compared with non-bioadhesivecapsules. The bioavailability of naftopidil in dogs was improved hy using bioadhesion.