Iontophoresis - an approach for controlled drug delivery: a review.

The recent approval of lidocaine hydrochloride and epinephrine combined iontophoretic patch (Lidosite Vysteris Inc.) for localized pain treatment by FDA has invigorated the gaining interest in iontophoretic drug delivery systems for the transdermal delivery of drugs. This technique of facilitated movement of ions across a membrane under the influence of an externally applied electric potential difference, is one of the most promising physical skin penetration enhancing method. The rationale behind using this technique is the capability of this method to increase the systemic delivery of high molecular weight compounds with controlled input kinetics and minimum inter-subject variability, which is otherwise achieved only when parentral route of administration is used. Recently, good permeation of larger peptides like insulin has been achieved through this technique in combination with chemical enhancers. This review briefly describes the factors which affect iontophoretic drug delivery and summarizes the studies conducted recently using this technique in order to achieve higher systemic absorption of the drugs having low passive diffusion otherwise. The effect of permeation enhancers (chemical enhancers) on iontophoretic flux of drugs has also been described. Present review also provides an insight into reverse iontophoresis. Various parameters which affect the transdermal absorption of drugs through iontophoresis like drug concentration, polarity of drugs, pH of donor solution, presence of co-ions, ionic strength, electrode polarity etc. have also been reviewed in detail.