title: Physical characteristics and lipoprotein distribution of liposomal nystatin in human plasma.
abstract: The physical characteristics and lipoprotein distribution of free nystatin (NYS) and liposomal NYS (L-NYS) in human plasma were investigated. To determine the percentage of NYS that was lipid associated following incubation in human plasma, C18 reverse-phase extraction columns were used. To assess plasma drug distribution, NYS and L-NYS (20 microg/ml) were incubated in human plasma for 5, 60, and 120 min at 37 degrees C. After each interval, plasma was removed and separated into its lipoprotein and lipoprotein-deficient plasma (LPDP) fractions by ultracentrifugation and assayed for NYS by high-pressure liquid chromatography. Further studies evaluated the liposome structure of L-NYS by filtering through a 0.14-microm-pore-size microfilter before and after the addition of human plasma. When reconstituted L-NYS (mean particle diameter +/- standard deviation, 321 +/- 192 nm) was applied to a C18 column, 67% +/- 4% of the initial NYS concentration was associated with the lipid. When plasma samples containing L-NYS that had been incubated for 5 to 120 min at 37 degrees C were applied to C18 columns, 66 to 76% of the NYS was lipid associated. Incubation of NYS in human plasma for 5 min at 37 degrees C resulted in 3% +/- 1% of the initial NYS concentration incubated in the low-density lipoprotein (LDL) fraction, 23% +/- 4% of that in the high-density lipoprotein (HDL) fraction, and 66% +/- 10% of that in the LPDP fraction. In contrast, the distribution of NYS following incubation of L-NYS in human plasma for 5 min was 13% +/- 2% in the LDL fraction, 44% +/- 5% in the HDL fraction, and 42% +/- 5% in the LPDP fraction. Similar results were observed following 60 and 120 min of incubation. In addition, the liposome structure of L-NYS was quickly lost when mixed with plasma. These findings suggest that rapid disruption of the L-NYS structure upon incubation in human plasma is consistent with its rapid distribution in plasma. The preferential distribution of NYS into the HDL fraction upon incubation of L-NYS may be a function of its phospholipid composition.
authors.affiliation: Division of Pharmaceutics and Biopharmaceutics, Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, Canada. Kwasan@unixg.ubc.ca
authors.forename: K M
authors.initials: KM
authors.lastname: Wasan
authors.forename: M
authors.initials: M
authors.lastname: Ramaswamy
authors.forename: S M
authors.initials: SM
authors.lastname: Cassidy
authors.forename: M
authors.initials: M
authors.lastname: Kazemi
authors.forename: F W
authors.initials: FW
authors.lastname: Strobel
authors.forename: R L
authors.initials: RL
authors.lastname: Thies
mesh_terms: D000900:Anti-Bacterial Agents / Q000008:administration & dosage* / Q000097:blood* / Q000737:chemistry; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D008074:Lipoproteins / Q000097:blood*; D008081:Liposomes; D009761:Nystatin / Q000008:administration & dosage* / Q000097:blood* / Q000737:chemistry
chemical_list: D000900:Anti-Bacterial Agents; D008074:Lipoproteins; D008081:Liposomes; D009761:Nystatin