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Antimicrobial Agents and Chemotherapy, Sep 1997, 1871-1875, Vol 41, No. 9
KM Wasan, M Ramaswamy, SM Cassidy, M Kazemi, FW Strobel and RL Thies
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.
Copyright © 1997 by the American Society for Microbiology. All rights reserved.
Physical characteristics and lipoprotein distribution of liposomal nystatin in human plasma
Division of Pharmaceutics and Biopharmaceutics, Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, Canada. Kwasan@unixg.ubc.ca
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