Topical iontophoretic delivery

At present, transdermal iontophoresis is used in the topical delivery of local anesthetics and anti-inflammatory agents. The treatment of hyperhidrosis and the diagnosis of cystic fibrosis are other clinical applications of iontophoresis. Also, a glucose-monitoring device has been developed utilizing the principle of reverse iontophoresis. Commercial iontophoretic systems that would continuously deliver therapeutic agents into the systemic circulation, corresponding to the passive transdermal patches, do not exist at the moment; however, Alza Corporation has announced that it has received an approvable letter from the US FDA regarding a new drug application for Ionsys®, an iontophoretic, fentanyl-containing, transdermal analgesic. There is currently a lot of interest in the potential of closed-loop systems, which not only sense changes in the concentration of the analyte in the skin and in the subdermal tissues, but also administer a drug in response to the fluctuating concentration/need. Thus, self-regulated or patient-regulated systems that allow medication to be administered at home would enable controlled therapy, while accounting for the individual needs of the patient. Predictable and controlled non-invasive drug delivery on the one hand, and putative adverse effects on the other, determine the success of topical iontophoretic systems and methods. The often unavoidable skin sensitization/irritation and other adverse reactions have to be related to the therapeutic benefit(s) of (bio)molecule administration; for example, the potential for skin irritation associated with pain control medication is quite different (in terms of acceptability) to skin irritation associated with cancer treatment. An additional obstacle in the path to successful transdermal delivery is the stability issue of the (bio)molecule in the drug delivery system, skin, and target tissue.