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Iontophoresis, also called electromotive drug administration (EMDA), is a technique using a small electric charge to deliver a medicine or other chemical through the skin. It is basically an injection without the needle. The technical description of this process is a non-invasive method of propelling high concentrations of a charged substance, normally a medication or bioactive agent, transdermally by repulsive electromotive force using a small electrical charge applied to an iontophoretic chamber containing a similarly charged active agent and its vehicle. One or two chambers are filled with a solution containing an active ingredient and its solvent, also called the vehicle. The positively charged chamber, called the anode, will repel a positively charged chemical, whereas the negatively charged chamber, called the cathode, will repel a negatively charged chemical into the skin.
Iontophoresis is well classified for use in transdermal drug delivery. Unlike transdermal patches, this method relies on active transportation within an electric field. In the presence of an electric field electromigration and electroosmosis are the dominant forces in mass transport. These movements are measured in units of chemical flux, commonly µmol/cm2h.
Reverse iontophoresis is the process by which molecules are removed from within the body for detection. In reverse iontophoresis, the negative charge of the skin at buffered pH causes it to be permselective to cations, causing solvent flow towards the anode. This flow is the dominant force, allowing movement of neutral molecules, including glucose, across the skin. This technology is currently being used in such devices as the GlucoWatch, which allows for blood glucose detection across skin layers using reverse iontophoresis.
Iontophoresis is commonly used by physical therapists for the application of anti-inflammatory medications. Common diagnoses treated with Iontophoresis include plantar fasciitis, bursitis, and some types of hyperhidrosis. In this specific application, the solution chosen is usually tap water, but better results can be obtained using glycopyrronium bromide, a cholinergic inhibitor. Iontophoresis of acetylcholine is used in research as a way to test the health of the endothelium by stimulating endothelium-dependent generation of nitric oxide and subsequent microvascular vasodilation. Acetylcholine is positively charged and, therefore, placed in the anode.