Can anyone suggest a method to evaluate the amount of drug in microspheres drug-polymer? I mean: I produce coprecipitates made of an high water soluble polymer and a poorly water soluble drug to improve its bioavailability. In these microspheres, drug is dispersed in the polymeric matrix and I want evaluate how much is the amount of drug in the internal and in the external part of the microspheres. Does anyone know some Pharmacopeia methods?
You can try dialysis, provided that you design the experiment before hand with possibilities in going the experiment wrong way and try on a smaller scale!. the precipitates and non-precipitates can be easily estimated using instrumentation based analyses, spectrophotometry, UV, HPLC, and also GC if your drug is volatile enough or have a lower melting point.
Hi Allesia,
Since these are microspheres; the best mode i can suggest is to go for either centrifugation or dialysis.
Centrifugation would be more rapid and convenient.
Prepare the microspheres using known amount of drug (X mg). make Microspheres.
Take microsphere suspension (containing drug loaded microspheres and free drug) and centrifuge it (say 10000 RPM for 30 min).
Separate out the supernatant and determine the amount of drug in supernatant; and it will represent free or unloaded or as you said external drug (X1).
Now determine the amount of drug loaded inside licrosphere as: X-X1
Hope this helps.
Wishes
Rakesh
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