A COMPARATIVE-STUDY ON THE PULMONARY DELIVERY OF TOBRAMYCIN ENCAPSULATED INTO LIPOSOMES AND PLA MICROSPHERES FOLLOWING INTRAVENOUS AND ENDOTRACHEAL DELIVERY

The use of carriers to deliver tritiated tobramycin via intravenous an d endotracheal routes to the lungs was investigated. Pulmonary, renal and vascular distribution were monitored at 6 and 24 h. The results in dicated a significant difference (p < 0.05) between free drug, which i s rapidly disseminated to other organs, specifically kidney, and lipos omal and microcapsular tobramycin which was primarily retained in the lungs. Renal drug levels of intravenously delivered microcapsular tobr amycin were significantly higher than those produced by liposomal admi nistration at 6 (p less than or equal to 0.025) and 24 h (p less than or equal to 0.05). Liposomes however, produced pulmonary levels three times higher than those of the free drug both at 6 (p less than or equ al to 0.025) and 24 h (p less than or equal to 0.025). At 24 h renal d rug levels following endotracheal delivery were lower for both encapsu lated forms than for the free drug (p less than or equal to 0.005). Co nversely, pulmonary drug levels were higher following encapsulated dru g administration compared to those following free drug delivery at 24 h (p less than or equal to 0.005). These results demonstrate that tobr amycin can be retained in the lung by means of liposomal and microenca psulated delivery systems after endotracheal delivery.