On Tue, 21 Jul 1998, Benoit Turcot wrote:
> [log in to unmask],Internet writes:
> >Dexamethasone is an anion (negative charge), and should be delivered from
> >the cathode (negative pole).
> Frank Underwood
>
>
>
> Humm! My reference mentioned in an earlier message (clinical electrotherapy,
> second edition) states that Dexamethasone (from Decadron) has a positive charge
> and should be used on the anode - the positive electrode.
>
> Our information is contradictory. Can somebody "doublecheck" the polarity of
> Dexamethasone ?
>
> Benoit Turcot
>
Check the following reference regarding dexamethasone sodium phosphate:
Petelenz TJ, Buttke JA, Bonds C, Lloyd LB, Beck JE, Stephen RL, Jacobsen
SC, Rodriguez P: Iontophoresis of dexamethasone: Laboratory studies.
Journal of Controlled Release 20:55-66, 1992.
"...forms a mixture of mono- and di-anionic species. . . . Thus, during
iontophoresis in aqueous solution it is expected to move from the negative
towards the positive electrode."
You are correct in that the information in textbooks is contradictory;
however, I have yet to find a textbook that cites a primary reference
(such as the Petelenz paper) to support statements regarding the polarity
of dexamethasone. If you consider the structure of the molecule, it is
pretty apparent that it is an anion. There are two sodium ions that
dissociate from two phosphate groups, leaving a negatively charged
molecule.
Frank Underwood
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