Preparation and pharmacodynamic evaluation of liposomes of indomethacin.
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abstract
The side effects of indomethacin, such as ulceration of the kidney and central nervous system (CNS) toxicity, limit its use as a drug for rheumatoid arthritis. Encapsulation of this drug in liposomes may reduce the toxic effects. The aim of this study was to determine the factors influencing encapsulation of indomethacin in liposomes and to determine anti-inflammatory potential of liposomal indomethacin. A series of liposomal formulations of indomethacin were prepared using various phospholipids. The effects of method of preparation, lipid composition, charge, and cholesterol (CH) on encapsulation of indomethacin in liposomes were investigated. A significant variation in encapsulation of the drug in liposomes was observed when prepared by different methods. With all the methods of preparation tried, the favorable lipid composition for high encapsulation of this drug was egg phosphatidyl choline:CH: stearlyamine (PC:CH:SA) at a 1:0.5:0.1 molar ratio. Inclusion of cholesterol did not affect the encapsulation efficiency of the drug in liposomes. The drug release profile from the liposomes was biphasic, and the highest percentage drug release was observed with large unilamellar vesicles (LUVs) (100 nm). Inclusion of stearylamine (PC:CH:SA 1:0.5:0.1) and phosphatidyl glycerol (PG) (PC:CH:PG 1:0.5:0.2) in the liposomes reduced the release of the drug in comparison to the neutral liposomes (PC:CH 1:1). The slow release of the drug from stearylamine-containing liposomes may be explained by the electrostatic interaction between the acid moiety of the drug and the amine moiety of the lipid. It is assumed that the possible hydrogen bonding between--OH groups of phosphatidyl glycerol and the--COOH group of the drug might be the reason for the slow release of the drug from PC:CH:PG (1:0.5:0.2) containing liposomes. Pharmacodynamic evaluation of the liposomes was performed by carrageenan-induced rat paw edema (acute) and adjuvant arthritis (chronic) models. The anti-inflammatory activity was increased from the first to fifth hour PC:CH:PG (1:0.5:0.2) and PC:CH:SA (1:0.5:0.1) liposomes showed the highest percentage inhibition of edema. In both these models, anti-inflammatory activity of liposomal indomethacin was significantly higher than that of free indomethacin (p < .01). The ulcer index of the free drug was about three times more than the encapsulated drug when administered at the same dose intraperitoneally to arthritic rats consecutively for 21 days.
