Diagnostic and therapeutic applications of iontophoresis

Owing to the excellent barrier properties of the stratum corneum, transdermal delivery remains a challenge for a high number of molecules. Iontophoresis is a noninvasive technique which uses a low current to administer polar and charged species through the skin, thereby enlarging the range of drug candidates for transdermal administration. Unlike other techniques of transdermal delivery enhancement, iontophoresis acts on the molecule itself allowing a better control of the dose applied. The symmetry of the technique can be employed for controlled extraction, allowing a relation to be established between extracted flux and subdermal concentration. This opened the way for innovative applications, notably in the field of noninvasive monitoring of glucose and xenobiotics. Rather than being an extensive review of the literature, this article summarizes the basic rules governing iontophoretic transport, discusses advantages and limitations of the technique, and provides an overview of promising therapeutic applications.