Sevelamer
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Randy Holmes-Farley
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It is intense competition from sulfate and chloride (IMO). I tried it and it failed to bind much phosphate from seawater.
It also works best in the range of a few mM (few tenths of ppm phosphate) and even at GI tract levels of chloride (say, 5,000 ppm), loses a lot of its capacity at below 1 mM (0.1 ppm phosphate).
For those who don't know, sevelamer is one of my approved human pharmaceuticals, crosslinked polyallylamine, which is approved for treating elevated phosphate in humans. It is a highly positively charged polymer that binds the negative charges on phosphate.
Randy Holmes-Farley
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FWIW, sevelamer is somewhat selective for phosphate over chloride because HPO4-- can fit nicely against two positive charges in the polymer, while chloride only has a single charge and cannot be bound that way.
Sulfate (SO4--), with two negative charges on oxygens spaced apart by one atom, looks quite similar to the form of phosphate sevelamer would bind at pH 8 (mostly HPO4--), so will compete very strongly. Sulfate isn't significant in the GI tract.
Sulfate (SO4--), with two negative charges on oxygens spaced apart by one atom, looks quite similar to the form of phosphate sevelamer would bind at pH 8 (mostly HPO4--), so will compete very strongly. Sulfate isn't significant in the GI tract.
Randy Holmes-Farley
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You talking about in people? I’m not sure there is a “big” problem, but The main reported issue with lanthanum is the small amount that gets absorbed and ends up in bones.
