A comparative study on the pulmonary delivery of tobramycin encapsulated into liposomes and PLA microspheres following intravenous and endotracheal delivery

Abstract

The use of carriers to deliver tritiated tobramycin via intravenous and endotracheal routes to the lungs was investigated. Pulmonary, renal and vascular distribution were monitored at 6 and 24 h. The results indicated a significant difference (p < 0.05) between free drug, which is rapidly disseminated to other organs, specifically kidney, and liposomal and microcapsular tobramycin which was primarily retained in the lungs. Renal drug levels of intravenously delivered microcapsular tobramycin were significantly higher than those produced by liposomal administration at 6 (p ≤ 0.025) and 24 h (p ≤ 0.05). Liposomes however, produced pulmonary levels three times higher than those of the free drug both at 6 (p ≤ 0.025) and 24 h (p ≤ 0.025). At 24 h renal drug levels following endotracheal delivery were lower for both encapsulated forms than for the free drug (p ≤ 0.005). Conversely, pulmonary drug levels were higher following encapsulated drug administration compared to those following free drug delivery at 24 h (p ≤ 0.005). These results demonstrate that tobramycin can be retained in the lung by means of liposomal and microencapsulated delivery systems after endotracheal delivery.