Encapsulation, pharmacokinetics and tissue distribution of interferon α-2b liposomes after intramuscular injection to rats

The aim of the present study was to investigate the effect of liposome-encapsulation and liposome-size on the in vivo pharmacokinetics of interferon α-2b (IFNα-2b) following i.m. administration to rats, and whether there was any liver-targeting of these liposomes. Since liposomes of different sizes can be obtained by homogenization, the effect of homogenization on the IFNα-2b activity was also investigated. The pharmacokinetics of IFNα-2b solution (12.8 μg/kg) and IFNα-2b prepared in liposomes, including three mean sizes of 172 nm (12.2μg/kg), 113 nm (44.2, 11.0, and 2.8μg/kg, respectively), and 82 nm (13.1 μg/kg), were studied after a single i.m. dose to rats. Compared to a solution of IFNα-2b. administration of liposomal IFNα-2b resulted in a significantly prolonged tmax, the apparent elimination half life (t1/2β) was 2.3 times longer, both AUC0-∞ and MRT0-∞ were also clearly enhanced and greater accumulation was obtained in the liver (p < 0.05). The AUC0-∞ increased proportionally to the administered dose of IFNα-2b liposomes. Moreover, the size of liposomes ranging from 82 nm to 172 nm had no significant difference on the pharmacokinetic behavior in vivo (p > 0.05). In sum, compared with the free form, IFNα-2b encapsulated in liposomes can alter strikingly the pharmacokinetics properties following i.m. injection and if a liposomal size ranging from 82 nm to 172 nm was used, consistent pharmacokinetic behaviors of IFNα-2b was exhibited. The liposomal formulation apparently targeted the liver, offering a potential advantage for hepatitis B treatment.