Targeting of multiple emulsions to the lungs.

The conventional W/O/W emulsions are readily taken up by the reticuloendothelial system (RES) so that it is necessary to develop either stealth type or tissue specific multiple emulsion for effective targeting. A multiple emulsion system W/O/W containing rifampicin as encapsulant (W/O/W) was prepared. The droplet size was kept small to study targeting independent of passive embolism of larger droplets in the lung capillaries. It was characterised in vitro for drug release through a treated cellophane membrane. A prolonged first order drug release was observed. The W/O/W multiple emulsion system was coated with an o-palmitoyl derivative of mannan (mol.wt. 20,000) to assess its toxicity in vitro and its distribution behaviour in vivo. The multiple emulsion was found to be non toxic at 0.2 ml formulation/10(6) cells level in presence or absence of serum. An intravenous injection of the polysaccharide coated multiple emulsion was given and the tissue distribution of the drug after 1 h and 24 h was investigated. A significant enhancement in lung uptake and a decreased internalisation by spleen was noticed.