Chromatography Forum

The USP pantoprazole sodium RS is sesquihydrate form. The label describes "use a value of 0.943 mg of pantoprazole sodium per mg of material on the as is basis". Does the "0.943 mg of pantoprazole sodium" on the label mean pantoprazole sodium or pantoprazole sodium sesquihydrate??

Check the relative molecular weights (i.e., with and without the water).

Reference Standards
Lili Wang, Technical Services Scientist
1-301-816-8129
RSTech@usp.org

This person is listed as the Reference Standards contact in the USP Monograph for Pantoprazole Sodium, which uses this standard in its methods, should you choose to contact USP.

The other USP Technical Services Scientist replied me. she said, "the description "0.934 mg of pantoprazole sodium" refers to the material in the sesquihydrate form. My English is not good enough to relize it. Does she mean "pantoprazole sodium wrote in the description of label is pantoprazole sodium sesquihydrate ?? or it's just pantoprazole sodium(not sesquihydrate form)??

It's like the question: what's the maximum the water content can be in 99.5% USP glycerin. I find that the USP is very confusing throughout, like many of their monographs try to economize on number of characters printed or something. When I've E-mailed the USP contacts for clarification, all I've gotten back is "see such and such section". It's very discouraging, and so many of the assays are wet chemistry assays and decades obsolete. And so much is directed on manufacturers of an active, not on the actual assay of such active in a finished product.

Anyway, 99.5% USP glycerin can be up to 5.0% water. Apparently the 99.5 refers to anyhrous product somehow. Tell me if that makes sense.

For what it's worth:
pantoprazole sodium. MW = 383 (http://en.wikipedia.org/wiki/Pantoprazole)
Add 1.5 moles of water (27) gives a MW for the sesquihydrate of 410

383/410 = 0.934

What do you want to bet that a dyslexic writer started with that?

I think that the reply by USP Technical Services Scientist makes me confuse. Depending on her explanation, "0.934mg of pantoprazole sodium" seems to be 0.934mg of pantoprazole sodium sesquihydrate. However, I don't think so. As Mr. jupille said, calculate the Mw ratio of pantoprazole sodium with or without crystalline water. But I don't understand why the Mw are 383 and 410. The Mw of pantoprazole sodium should be 405 and sesquihydrate form should be 432, the ratio is 0.9375, it's close to 0.934!? Back to the reference standard, if the 0.934 mg of pantoprazole sodium is sesquihydrate form, the resilt of assay in raw material would be percentage of pantoprazole sodium sesquihydrate. So the assay on the anhydrous basis would be low, it doesn't make sense.

The USP pantoprazole sodium RS is sesquihydrate form. The label describes "use a value of 0.943 mg of pantoprazole sodium per mg of material on the as is basis".

the USP RS is pantoprazole sodium sesquihydrate. while using this USP RS, each mg contains 0.943 mg pantoprazole sodium, not the sesquihydrate.

you are right. Thank you very much and thank you all.