Abstract
A gelatin sphere-in-oil-in-water (S/O/W) multiple emulsion was prepared by dispersing primary sphere-in-oil (S/O) emulsion into an external aqueous phase and its potential for prolonging parenteral absorption of bleomycin was studied in rats and rabbits. Intramuscular injection of bleomycin in an S/O/W emulsion formulation provided a sustained plasma concentration which was almost equal to those obtained after injeotion of S/O emulsion and oily suspension, while immediate appearance of bleomycin in plasma and subsequent rapid clearance were observed following intravenous or intramuscular injection of aqueous drug solution. The prolonged release of bleomycin from the multiple emulsion was confirmed by observation of the retarded disappearance of the drug from the injection site. S/O/W emulsion also exhibited enhanced lymphatic transfer of bleomycin following injection into the appendix of rabbits. These results show the potential of S/O/W emulsion as a parenteral dosage form in addition to its superior injectability. The possibility that the instability of multiple emulsions during storage could be at least partly overcome by employing lyophilization processing was demonstrated.
