iontophoresis

Many chemicals are charged, either positively, or negatively. As everyone knows, like charges repel. If a drug of a certain charge is put on the skin, and a similar charge placed above it, the only direction it can move is down. It may seem illogical that the skin could be penetrated, because we think of it as solid. However, this is happening on the molecular level, and so drug molecules can go through the top layer of skin, the stratum corneum. Once through their they can be absorbed, and have an effect.

Iontophoresis is only suitable for treatment of conditions that occur locally. The drug must be placed exacly where it is needed, as it does not enter the blood supply and circulate round the body. The most common conditions that can be treated with iontophoresis are localised skin disorders. It can also be used to deliver a limited local anaesthetic.

Some drugs can be delivered at a controlled rate by wearing a wristband that passes a current through the skin, causing gentle iontophoresis.

Indeed, the prime use today of iontophoresis may be the treatment of hyperhidrosis. A variety of drugs (generally anticholinergics have been delivered through the skin via iontophoresis to help stop sweat, and this treatment works. However, in the studies performed, the control group which received only tap water did quite well - better than merely placebo effect.

It turns out, the current itself has some therapeutic effect on hyperhidrosis, and tap water iontophoresis has gained an important role in the treatment of hyperhidrosis.

It is thought that the skin surrounding sweat glands may become hyperkeratotic, blocking the pores; this has not been properly demonstrated, and may or may not be the true mechanism.

Naturally, distilled water would not be suitable for iontophoresis, since current cannot be conducted well without ions present.