Development and evaluation of a dry powder formulation of liposome-encapsulated oseltamivir phosphate for inhalation.

This study aims to develop oseltamivir phosphate (OP) liposomes as inhalation powders by spray-drying based on the single factor investigation, which was mainly composed of lactose, L-leucine and mannitol. It was found that the ratio of OP and liposomes (1:10), inlet temperature (110 °C) and airflow rate (2.3 mL/min) showed optimized physical properties of OP liposomes. Deposition was evaluated after the aerosolization of powders at 600 L/h via the Aerolizer® into a twin-stage impinger. The concentrations of OP and oseltamivir carboxylate (OSCA) in rats plasma using LC-MS have been determined and performed via pharmacokinetic software DAS 2.0 package. The liposomal OP dry powders displayed an average particle size around 3.5 µm with fine particle fraction (FPF = 35.40%). In vitro evaluation demonstrated a sustained release pattern accounting for 20% drug release compared to that of OP solution up to 90% drug release in 2 h. And the cumulative release percentage was up to 50% in 20 h. Atrioventricular fitting results indicated that all preparations were best fitted with a two-compartment model. There was a significant difference in MRT, Cmax and Tmax (p < 0.01) between the two groups of liposomal OP dry powders and OP solution with t-test, which indicated that the drug released slowly from liposomal OP dry powders in the lung. To sum up, dry powders formulation of liposome-encapsulated OP for inhalation was suitable for pulmonary administration, which offering the opportunity to reduce dosing frequency.