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The following message was posted to: PharmPK
Dear Sir
I have a problem regarding the selection of dissolution media for the
following.
Sodium alginate when treated with calcium forms water insolube gel.
Several papers have described the use of calcium alginate for
controlled release of actives. however no uniformity with regards to
the selection of dissolution mediawas seen. some have used 0.1 N HCl
, some tris phosphate buffer, some have used distilled water etc. The
alginates are practically insoluble in acidic pH and swell and
release the contents only when the pH is raised. In intestinal fluid
though the pH is high, it also contains ions like phosphateswhich
have high affinity for calcium than alginate. this causes a faster
opening / breakdown of cross links than in plain water (where simple
leaching of calcium occurs). Calcium phaosphate being insoluble in
water further shifts the equlilibrium and increases the rate of
reaction. the rate of reaction is concentration dependent therefore
even if we use phosphate buffer, the intestinal phosphate content
should be considered. these factors will surely affecxt the IVIVC.
I would like to have expert comments in this regard.
Vinay B. Patil,
Senior Research Fellow,
Poona College of Pharmacy,
Erandwane, Pune 411038
Maharashtra. India
vbp_76.at.hotmail.com
Back to the Top
The following message was posted to: PharmPK
Dear Sir
I have a problem regarding the selection of dissolution media for the
following.
Sodium alginate when treated with calcium forms water insolube gel.
Several papers have described the use of calcium alginate for
controlled release of actives. however no uniformity with regards to
the selection of dissolution mediawas seen. some have used 0.1 N HCl
, some tris phosphate buffer, some have used distilled water etc. The
alginates are practically insoluble in acidic pH and swell and
release the contents only when the pH is raised. In intestinal fluid
though the pH is high, it also contains ions like phosphateswhich
have high affinity for calcium than alginate. this causes a faster
opening / breakdown of cross links than in plain water (where simple
leaching of calcium occurs). Calcium phaosphate being insoluble in
water further shifts the equlilibrium and increases the rate of
reaction. the rate of reaction is concentration dependent therefore
even if we use phosphate buffer, the intestinal phosphate content
should be considered. these factors will surely affecxt the IVIVC.
I would like to have expert comments in this regard.
Vinay B. Patil,
Senior Research Fellow,
Poona College of Pharmacy,
Erandwane, Pune 411038
Maharashtra. India
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Copyright 1995-2010 David W. A. Bourne (david@boomer.org)