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Combination of Microneedles with Other Methods
Published in Boris Stoeber, Raja K Sivamani, Howard I. Maibach, Microneedling in Clinical Practice, 2020
Transdermal iontophoresis refers to application of physiologically acceptable electric current (< 0.5 mA/cm2) to enable movement of charged or ionized molecules into or across a membrane (15). This delivery method is suitable for polar molecules with high charge density. The amount of drug delivered via iontophoresis is proportional to the intensity of the current applied across the tissue (15). Iontophoretic transport is governed by two major mechanisms, electromigration and electroosmosis. Detailed information on the transport mechanisms and specific applications of iontophoresis can be found in these review articles (6, 15–17). One of the key features of iontophoretic delivery is its ability to be tailored to an individual's dose requirements. Drugs can be delivered in a continuous or a pulsatile fashion by programming the current (15). However, there are limitations to iontophoresis, one of the biggest of which is that it can only deliver molecules up to approximately 15 kDa in size (18–22).
Iontophoresis: Applications in Drug Delivery and Noninvasive Monitoring *
Published in Richard H. Guy, Jonathan Hadgraft, Transdermal Drug Delivery, 2002
M. Begoña Delgado-Charro, Richard H. Guy
The main limitation for iontophoresis resides nevertheless in the range of molecules for which an efficient enhancement is achievable. Equation (2) predicts low transport numbers for large drugs, because of their poor performance as charge carriers. As will be discussed below, for these drugs the main mechanism of electrotransport is convective flow (electroosmosis), which may be considered (to a first approximation) to be independent of the molecular size (7). Unfortunately, this mechanism of transport is much less efficient than electromigration. There have therefore been attempts to combine iontophoresis with other enhancement techniques, such as chemical promoters and electroporation (14,32). While such combinations have induced greater deliveries, they have equally caused more significant damage to the barrier and a consequent loss of the control inherent in the iontophoretic approach.
Non-invasive targeted iontophoretic delivery of cetuximab to skin
Published in Expert Opinion on Drug Delivery, 2020
Maria Lapteva, Marwa A. Sallam, Alexandre Goyon, Davy Guillarme, Jean-Luc Veuthey, Yogeshvar N. Kalia
CTX labeling and microscopic visualization in skin suggested that CTX penetrates via two main pathways: the follicular pathway and the intercellular pathway. It has already been hypothesized that iontophoretic enhancement of molecular transport relies on the creation of transient transport channels due to the reorientation of stratum corneum lipids under the application of an electric field [35,36]. In addition to this mechanism, appendageal structures including PSUs, may act as less resistive gateways for the transient channels to be created [35]. However, the role of appendageal pathways has mainly been evoked in the context of electromigration; the presence of an appendageal electroosmotic flow and its relevance for the transport of neutral molecules still need to be investigated. The relative contributions of EM and EO to electrotransport through bulk skin and the appendageal structures (e.g. PSU) may be different: since EO requires the presence of fixed negative charges to create solvent flow then if the population of bulk charges is less in the PSU, convective solvent flow and hence the EO will be diminished. However, the iontophoretic-targeted follicular administration of therapeutic antibodies could greatly serve the management of autoimmune diseases affecting the PSU, such as alopecia areata [37].