Abstract
Cyclosporin A, a non-polar cyclic polypeptide, was incorporated successfully in a positively-charged submicron emulsion delivery system. Physicochemical characterizations such as particle size (220-240 nm), creaming rate and drug content suggested that the submicron emulsion formulation was able to withstand thermic and mechanical shocks while showing virtually no sign of drug nanoprecipitation or crystallization within the emulsion upon storage at 4, 25 and 37°C over a period of up to six months although cyclosporin is notorious for its tendency to precipitate out in conventional oil/water systems in which it is fully dissolved initially. The drug probably has a reasonably high degree of drug solubilization in the inner oil core phase of the emulsion preventing the crystallization. However, the pH and zeta potential of the final emulsion decreased progressively at the highest storage temperature studied compared to the lower temperatures, during the stipulated storage time. This most probably indicates the formation of free fatty acids from phospholipids present in the formulation, which are known to reduce the emulsion pH value, leading to a decrease in the absolute zeta potential value but without reversing the charge.
Original language | English |
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Pages (from-to) | 421-426 |
Number of pages | 6 |
Journal | S.T.P. Pharma Sciences |
Volume | 11 |
Issue number | 6 |
State | Published - 2001 |
Keywords
- Cyclosporin A
- pH
- Stability
- Submicron emulsion
- Zeta potential