Liposomal pulmonary drug delivery. I. In vivo disposition of atropine base in solution and liposomal form following endotracheal instillation to the rabbit lung.

The potential of liposomes as carriers for local pulmonary drug delivery was investigated in the rabbit. Atropine base, a model compound for lipophilic drugs, was encapsulated in neutral MLVs and sprayed at the bifurcation of the trachea. Drug concentrations determined in the lung indicated liposomal encapsulation provided higher drug concentrations within pulmonary tissue for a more prolonged period of time as compared to the solution form. Comparison of drug levels in plasma and appearance of drug in urine demonstrated more rapid systemic absorption and elimination of 'free' drug. Greater accessibility of drug in solution to the systemic circulation was reflected in higher atropine concentrations in all internal organs studied. Liposome encapsulation favourably altered the disposition of atropine base when locally administered to the rabbit lung.