Abstract 11

Journal of Controlled Release, 20:55-66, 1992.

Iontophoresis of Dexamethasone: Laboratory Studies

T.J. Petelenz, J.A. Burtke, C. Bonds, L.B. Lloyd, J.E. Beck,
R.L. Stephen, S.C. Jacobsen and P. Rodriguez
Iomed, Inc. Department of Surgery-University of Utah Medical Center, and
Center for Engineering Design-University of Utah, Salt Lake City, Utah

We have demonstrated the dexamethasone sodium phosphate (DmNaP) is delivered most efficiently from the negative electrode by iontophoresis, but, under certain conditions, the delivery from the positive electrode by electroosmosis can be accomplished. The laboratory data indicate that more dexamethasone is delivered per mA-min by iontophoresis than by electtoomosis, thus the same amount of drug can be administered in a shorter time from the negative electrode. Electrodes containing a hydrogel material, which restricts bulk water transport, delivered DmNaP most efficiently from the electrode of a negative polarity. When DmNaP is to be delivered in a mixture with another drug such as lidocaine, selection of the clinical treatment protocol depends on the desired therapeutic effect on the iontophoreic electrode which is to be used. When minimization of total treatment time is not critical, switching polarity of the electrode during the treatment can be used to administer drugs of opposite polarity from a mixture. Since co-iontophoresis of different compounds is often necessary for fully effective therapy, further research to understand the mechanism of simultaneous transport of various drugs is required.

?When the TransQ type gel electrode was used with a mixture of DmNaP and lidocaine, significantly more dexamethasone (14 +/- ug) was transported from the negative than from the positive (2 +/- 1 ug) electrode.

?Without admixture of lidocaine the total amount of transport (of dexamethasone) from the negative electrode (29 +/- micrograms) was significantly greater still.

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