Transdermal iontophoretic drug delivery: mechanistic analysis and application to polypeptide delivery

Three factors are of primary importance in determining the iontophoretic flux of a charged solute: the electrochemical potential gradient across the skin, an increase in skin permeability to passive transport due to iontophoresis (loosely defined as skin damage), and a current-induced water flux. The latter two factors can also affect the transport of uncharged solutes during iontophoresis. A method of correcting for the skin damage effect is introduced. The contributions of the water transport effect relative to that of the applied voltage drop for charged solutes is estimated. It is shown that the water transport contribution is generally lower than the contribution due to the applied voltage drop. The observed iontophonetic flux of the enhancement factors due to the applied voltage drop alone are compared with the theoretical predictions based on the constant field assumption. It is shown that the theoretical predictions are higher than the experimental observations. This work also examines, for the first time, a synergism of iontophoresis and pretreatment with a chemical penetration enhancer as a means for delivering high molecular weight polypeptides. It is shown that a 2-h pretreatment with absolute ethanol followed by iontophoresis dramatically increases the permeability coefficient of insulin through human skin.     

Combined strategies for enhancing the transdermal absorption of midazolam through human skin

Objectives Midazolam administration by intravenous or intramuscular injection produces pain and stress. For this reason, alternative methods of administration have been proposed. The transdermal administration of midazolam could improve patient comfort, which is especially important for children in the pre‐operative period. We aimed to assess the effect of iontophoresis and chemical percutaneous enhancers applied individually and together, to determine if a synergistic effect is achieved when both enhancement techniques are simultaneously employed. Methods This work reports the characterization of the passive diffusion of midazolam hydrochloride through human skin in vitro and evaluates the effect of iontophoresis application and chemical percutaneous enhancers on said diffusion when employed both individually and in combination. Key findings Percutaneous absorption assays demonstrated that the physical technique of iontophoresis, when applied alone, moderately increased midazolam hydrochloride permeation flux through human skin, producing a similar effect to that obtained with R‐(+)‐limonene chemical enhancer. Among the strategies assayed, it was observed that Azone produced the most pronounced enhancement effect when applied separately. The combination of pre‐treatment with Azone and iontophoresis exhibited a higher capacity for enhancing the transdermal flux of midazolam through human skin than Azone alone. Conclusions In conclusion, when applied individually, Azone exhibited the greatest enhancement effect on the transdermal diffusion of midazolam of the various strategies assayed. The combination of Azone and iontophoresis produce the highest transdermal steady‐state flux of midazolam but no synergic effect was achieved when the two enhancement strategies were applied in combination, showing that although selecting the best conditions for iontophoresis application, it is less effective for augmenting the transdermal delivery of midazolam than the chemical enhancer Azone.     

Investigation into the potential of iontophoresis facilitated delivery of ketorolac

The potential for iontophoresis facilitated transdermal transport of ketorolac was investigated using rat skin. Studies of electrical, physicochemical and device-related factors acting on the permeation kinetics of in vitro iontophoresis were performed. Iontophoresis increased the transdermal permeation flux of ketorolac as compared to the diffusion. Increase in applied current density or decrease in ionic strength of the donor solution enhanced the flux of the drug. Use of either platinum or silver/silver chloride electrodes resulted in similar enhancement of drug flux. Continuous current was more potent than pulsed current in promoting ketorolac transdermal permeation. Increasing the frequency or on:off ratio of pulse current induced an enhancement of the flux through the skin. An increase in donor drug loading dose or increasing the duration of current application resulted in enhancement of the drug flux. Pretreatment of the skin with D-limonene in ethanol or D-limonene in ethanol + ultrasound significantly enhanced the iontophoretic flux of the drug in comparison to passive flux with or without pretreatment. Trimodality treatment comprising of pretreatment with D-limonene in ethanol + ultrasound in combination followed by iontophoresis was found to be most potent for enhancing the rate of permeation of ketorolac.     

Modulated iontophoretic delivery of small and large molecules through microchannels

The objective of this work was to modulate transdermal drug delivery by iontophoresis though skin microchannels created by microneedles. Calcein and human growth hormone were used as a model small and large molecule, respectively. In vitro permeation studies were performed on porcine ear skin under three different settings: (a) modulated iontophoresis alone, (b) pretreatment with microneedles and (c) combination of microneedles pretreatment and modulated iontophoresis. For modulated iontophoresis, 0.5 mA/cm(2) current was applied for 1h each at 2nd and 6th hour of the study. Methylene blue staining, calcein imaging and pore permeability index suggested maltose microneedles created uniform microchannels in skin. Application of iontophoresis provided two peaks in flux of 1.04 μg/(cm(2)h) at 4th hour and 2.09 μg/(cm(2)h) at 8th hour of study for calcein. These peaks in flux were significant higher when skin was pretreated with microneedles (p<0.05). Similarly, for human growth hormone, modulation in transdermal flux was achieved with combination of microneedles and iontophoresis. This combination also provided significant increase in cumulative amount of calcein and human growth hormone delivered as compared to microneedles or iontophoresis alone (p<0.05). Therefore, iontophoresis can be used to modulate drug delivery across skin microchannels created by microneedles.     

Percutaneous Absorption Enhancement of Leuprolide

Chemical enhancers and vehicles were tested for their ability to improve the percutaneous absorption of leuprolide, a nonapeptide (luteinizing hormone releasing hormone analogue; MW 1209.4). In vitro permeabilities in nude mouse, snake, and cadaver skin were evaluated in either Franz diffusion cells or a Bronaugh flow-through system using an HPLC assay. Skin irritation caused by the formulations was evaluated in the rabbit. The chemical enhancer systems investigated strongly enhanced skin penetration of leuprolide. Maximum permeability enhancement of leuprolide acetate can be achieved with a nonirritating formulation containing ethanol, menthol, camphor, methyl salicylate, urea, and hydrogel. The in vitro permeability in nude mouse skin was 10 or 100 times higher than that obtained in cadaver skin, depending on the type of enhancer that was used in the formulation. Snake skin was at least 10 times less permeable than cadaver skin in this study. However, the effects of chemical enhancers on skin permeability were highly dependent on the skin model. Further, the in vitro permeability of leuprolide in the base form was 10 times higher than in the acetate form with the enhancers.     

Enhancement of nortriptyline penetration through human epidermis: influence of chemical enhancers and iontophoresis

Different known percutaneous chemical enhancers and iontophoresis have been tested in-vitro to study their ability to increase transdermal absorption of nortriptyline hydrochloride (20 mg mL(-1)). The chemicals 1-dodecanol, Span 20, Azone, (R)-(+)-limonene or isopropyl myristate were used as an overnight pretreatment at 5% (w/w) in ethanol. Furthermore, isopropyl myristate (20%, w/w) and propylene glycol (15%, w/w) were tested in the same vehicle. Iontophoresis was applied directly to the nortriptyline hydrochloride donor solution for three different concentrations (20, 2 and 0.5 mgmL(-1)). The chemical enhancers slightly increased the nortriptyline transdermal flux but iontophoresis was more efficient. In this case, nortriptyline transdermal flux was concentration dependent, having a higher flux when the concentration was lowered. Therefore, iontophoresis was the most suitable technique to increase transdermal absorption of nortriptyline and it could be an alternative method to provide therapeutic concentrations of this drug in smoking cessation treatment.     

渗透促进剂对胰岛素体外经皮离子导入渗透性的影响

本文考察了某些渗透促进剂如月桂氮Zhuo酮（AZ）、油酸（OA）、泊洛沙姆（POL）和丙二醇（PG）等对胰岛素体外经皮离子导入渗透性的影响。结果表明AZ对离子导入具有协同作用，PG能够增强这种作用，三者并用对胰岛素的经皮渗透具有特别显著的促渗效果。5％AZ／PG与离子导入并用后，较单独离子导入处理组的促渗因子为2.75。OA不能增强离子导入的作用，离子导入与某些渗透促进剂并用为胰岛素等大分子多肽类药物的透皮给药提供了新的思路和可能。     

Effect of iontophoresis and fatty acids on permeation of Arginine Vasopressin through rat skin

The aim of this study was to assess the effects of fatty acids and iontophoretic mode of penetration enhancement on transdermal delivery of Arginine Vasopressin (AVP). Sprague-Dawley (SD) rat skin was pretreated with fatty acids (e.g. 5% w/v, lauric acid, oleic acid, and linoleic acid in ethanol:water (EtOH:W, 2:1 system) for 2h and iontophoresis in vitro, separately or together. The results indicate that all fatty acids studied increased (P<0.05) the flux of AVP in comparison to control (not pretreated with enhancer) and their effectiveness in flux enhancement was comparable. Further, oleic acid in combination with iontophoresis significantly increased the permeation of AVP both in comparison to pretreatment with fatty acids and iontophoresis alone. However, iontophoresis did not further increase the permeation of AVP through linoleic acid pretreated skin. Fourier transform infrared (FT-IR) spectroscopic studies revealed that EtOH:W (2:1) system is not effective in lipid extraction. The shift to higher wavenumbers of the symmetric and asymmetric stretching peaks at 2850 and 2920cm(-1) revealed that at the concentration used, oleic acid and linoleic acid caused fluidization of stratum corneum (SC) lipids. This study provides direct evidence that oleic acid in EtOH:W (2:1) system causes disruption of the SC lipid lamellae and that a combination of oleic acid with iontophoresis further enhances the effects of oleic acid in a synergistic manner.     

Transdermal iontophoresis of sodium nonivamide acetate. V. Combined effect of physical enhancement methods

The effect of iontophoresis combined with treatment of other physical enhancement methods such as electroporation, low frequency ultrasound, and erbium:YAG (yttrium-aluminum-garnet) laser on the transdermal delivery of sodium nonivamide acetate (SNA) was examined in this present study. Iontophoresis increased the transdermal flux of SNA in vitro as compared to the passive diffusion without any enhancement. Furthermore, iontophoresis was always the most potent enhancement method for SNA permeation among the physical enhancement methods tested. Pulsing of high voltages (electroporation) followed by iontophoresis did not result in increased transport over iontophoresis alone. However, electroporation shortened the onset of transdermal iontophoretic delivery of SNA. Pretreatment of low frequency ultrasound (sonophoresis) alone on skin did not increase the skin permeation of SNA. The combination of iontophoresis and sonophoresis increased transdermal SNA transport more than each method by itself. The enhancement of drug transport across shunt routes and reduction of the threshold voltage in the presence of an electric field may contribute to this synergistic effect. Use of an erbium:YAG laser was a good method for enhancing transdermal absorption of SNA because it allows precise control of stratum corneum (SC) removal, and this ablation of SC could be reversible to the original normal status. The combination of laser treatment and iontophoresis also synergized the skin permeation of SNA, possibly due to a gradual drop in the electric resistance of the skin. The results in this present study point out that the choice of certain conditions with suitable physical enhancement methods can induce a synergistic effect on transdermal delivery of SNA during iontophoresis.     

Enhanced transdermal delivery of tetracaine by electroporation

The effect of electroporation on the transport of tetracaine through skin in vitro was studied using side-by-side compartment diffusion cells method. After achieving steady state by passive diffusion, fluxes of tetracaine achieved with passive diffusion, electroporative pulse and iontophoresis were compared. Electroporation (square-wave pulse, voltage 130 V, pulse time 0.4 s, pulse frequency 40 pulses min(-1)) or iontophoresis (0.2.mA cm(-2), lasting for 4 h) increased the transport of tetracaine through skin. The flux of tetracaine at 0.25 h after electroporation (pulse number 400) was 54.6+/-6.0 microg.cm(-2).h(-1), that after iontophoresis was 17.4+/-5.8 microg.cm(-2).h(-1) and that after passive diffusion was 8.2+/-0.5 microg.cm(-2).h(-1). In addition, the fluxes of tetracaine increased with the increasing of pulse number. From these results, it is clear that electroporation is effective in enhancing transdermal delivery of tetracaine and its function is better than iontophoresis.     

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.     

Transdermal delivery of levosimendan

The aim of this study was to determine if transdermal penetration of levosimendan, a novel positive inotropic drug, could be enhanced and controlled by formulation modifications. Penetration of levosimendan across human epidermis in vitro was determined using abdominal excised skin and diffusion cells. Predicted steady-state plasma concentrations of levosimendan were estimated using permeabilities and pharmacokinetic parameters of levosimendan. For penetration enhancement we used different pH values, co-solvents, cyclodextrins, surfactants, penetration enhancers, liposomes, and iontophoresis. Sodium lauryl sulfate, ethanol, oleic acid, and soya phosphatidylcholine or their combinations clearly increased levosimendan permeation across the skin in vitro. Iontophoresis was also an efficient method to increase transdermal permeation of levosimendan. A hydrophilic co-solvent/penetration enhancer is needed to achieve better permeability of levosimendan across the skin. In conclusion, transdermal delivery of levosimendan can be significantly increased by formulation modification. Based on kinetic calculations, therapeutic plasma concentrations may be achievable transdermally.     

Transdermal delivery of glibenclamide and glipizide: in vitro permeation studies through mouse skin

The purpose of this investigation was to study the feasibility of transdermal delivery of glibenclamide and glipizide. In vitro permeation of these drugs was studied through mouse skin using various penetration enhancers like Tween -20, polyethyleneglycol-400, ethanol and d-limonene by simultaneous application of drug and enhancer solution or by pretreatment of the skin with neat enhancer. The partition coefficient values indicated that both drugs partition well into the skin. Glipizide did not show any skin metabolism, while glibenclamide showed a minimal metabolism during in vitro skin metabolism studies. The flux values (microgram/cm2/h) of both drugs significantly (p < 0.05) increased in the presence of penetration enhancers. The glibenclamide flux values ranged from 1.39 +/- 0.13 without enhancer, to 19.01 +/- 2.14 in a combination of 50% ethanol and 5% d-limonene. Glipizide flux values ranged from 3.01 +/- 0.74 without enhancer, to 62.97 +/- 7.10 in a combination of 50% ethanol and 5% d-limonene. Skin retention and solubility of both drugs increased with all penetration enhancers compared to control. The target permeation rates for glibenclamide and glipizide were calculated to be 193.8 and 184.8 micrograms/h respectively. The present study showed that the target permeation rates for both drugs could be achieved with the aid of enhancers by increasing the area of application in an appreciable range.     

Occlusive and Non-Occlusive Application of Microemulsion for Transdermal Delivery of Progesterone: Mechanistic Studies

This work evaluated the occlusive versus non-occlusive application of microemulsion (ME) for the transdermal delivery of progesterone. The mechanisms of enhanced skin penetration were investigated. ME comprised of oleic acid, Tween 80, propylene glycol, and water, was used neat or with ethanol as a volatile cosurfactant. The ME formulations enhanced progesterone transdermal flux compared to the saturated drug solution in 14% aqueous propylene glycol (control). Ethanol-containing ME (EME) was better than the ethanol-free system (EFME). Open application of EFME produced a marginal reduction in flux compared to occlusive application. For EME, open application reduced the flux by 26–28% with the flux remaining significantly higher than that obtained with EFME. The mechanistic studies revealed synergism between ethanol and EFME with EME, producing greater flux than the sum of fluxes obtained from 40% ethanol in water and EFME. Penetration enhancement and supersaturation played a role in enhanced transdermal delivery, but other mechanisms were also possible. This study thus introduced EME as a transdermal delivery system for progesterone with good potential for open application as a spray.     

离子导入对卡托普利透皮吸收的促进作用(英文)

目的:研究离子导入技术对卡托普利透皮吸收的促进作用。方法:应用离子导入技术研究了卡托普利体外透过大鼠离体皮肤的影响因素,并进行了卡托普利水凝胶贴片大鼠在体的试验,测定了血药浓度的变化。结果:离子导入技术可以有效地促进卡托普利的透皮吸收,透皮速率增加约7倍。药物贮库中的各种因素如pH,离子强度,药物浓度和电流强度均影响药物的透皮速率。随着pH的增加,离子强度的减小,药物浓度的增加及电流强度的增加,透皮速率也增加。大鼠在体试验也表明用药1h后血药浓度即可达到坪值(约0.9μg/mL),并在整个试验阶段维持稳定。结论:离子导入可以有效地促进卡托普利的透皮吸收。     

Electrically enhanced transdermal delivery of a macromolecule

The purpose of this study was to establish the delivery parameters for the enhanced transdermal delivery of dextran sulfate (MW 5000 Da). Full-thickness pig skin or epidermis separated from human cadaver skin was used. Silver-silver chloride electrodes were used to deliver the current (0.5 mA cm-2). For electroporation experiments, one or more pulses were given using an exponential decay pulse generator. The correct polarity for iontophoresis and pulsing was first established as cathode in the donor. The amount of drug delivered increased with increasing donor concentration up to a point, but not any further. The amount delivered also increased with pulse voltage, the delivery being twice as much as with iontophoresis alone (144.5+/-10.35 microg cm(-2)), when 6 pulses of 500 V were applied at time zero before iontophoresis (276+/-45.2 microg cm(-2)). It was observed that the amount delivered was a function of increasing pulse length when the apparent charge delivered was kept constant. Transport through pig skin (107.4+/-24.4 microg cm(-2)) was found to be comparable with that through human epidermis (84.9+/-18.4 microg cm(-2)). In conclusion, we have demonstrated the transdermal delivery of a 5000 Da molecular weight dextran sulfate using iontophoresis. It was also seen that iontophoretic delivery could be enhanced by simultaneous electroporation.     

Ion-exchange and iontophoresis-controlled delivery of apomorphine

The objective of this study was to test a drug delivery system that combines iontophoresis and cation-exchange fibers as drug matrices for the controlled transdermal delivery of antiparkinsonian drug apomorphine. Positively charged apomorphine was bound to the ion-exchange groups of the cation-exchange fibers until it was released by mobile counter-ions in the external solution. The release of the drug was controlled by modifying either the fiber type or the ionic composition of the external solution. Due to high affinity of apomorphine toward the ion-exchanger, a clear reduction in the in vitro transdermal fluxes from the fibers was observed compared to the respective fluxes from apomorphine solutions. Changes in the ionic composition of the donor formulations affected both the release and iontophoretic flux of the drug. Upon the application of higher co-ion concentrations or co-ions of higher valence in the donor formulation, the release from the fibers was enhanced, but the iontophoretic steady-state flux was decreased. Overall, the present study has demonstrated a promising approach using ion-exchange fibers for controlling the release and iontophoretic transdermal delivery of apomorphine.     

Microporation and ‘Iron’tophoresis for Treating Iron Deficiency Anemia

Purpose

Iontophoretic mediated transdermal delivery of ferric pyrophosphate (FPP) in combination with microneedle pretreatment was investigated as a potential treatment for iron deficiency anemia (IDA).

Methods

In vitro transdermal delivery studies were performed using hairless rat skin and pharmacodynamic studies were performed in hairless anemic rat model. The hematological and biochemical parameters like hemoglobin, hematocrit and % serum transferrin were monitored in rats at healthy, anemic condition and post treatment. Micropores created by the microneedles were visualized in histological skin sections after staining with hemotoxylin and eosin. The recovery of micropores was investigated in vivo by measuring Transepidermal water loss (TEWL) at different time points.

Results

The passive, microneedle and iontophoresis mediated delivery did not lead to significant improvement in hematological and biochemical parameters in anemic rats, when used individually. When iontophoresis (0.15 mA/cm² for 4 hours) was combined with microneedle pretreatment (for 2 min), therapeutically adequate amount of FPP was delivered and there was significant recovery of rats from IDA.

Conclusions

Microneedle and iontophoresis mediated delivery of iron via transdermal route could be developed as a potential treatment for IDA. The transdermal controlled delivery of iron could become a potential, safe and effective alternative to parenteral iron therapy.     

Iontophoretic delivery of apomorphine: from in-vitro modelling to the Parkinson patient

Apomorphine is a mixed dopamine D1/D2 receptor agonist which is potentially useful in the treatment of Parkinson's disease. The delivery of apomorphine is however complicated because it is not absorbed orally and other delivery routes with the exception of the intravenous route seem to fail. The most interesting route for controlled delivery of apomorphine is transdermal iontophoresis because this could enable the Parkinson patient to directly control the needed amount of apomorphine by increasing or decreasing the drug input in order to achieve optimal drug therapy ('on-demand') with a minimum of toxic side effects. The typical features of Parkinson's disease could be used to monitor the needed drug input and even more elegantly by means of suitable chip sensors which are able to directly measure bradykinesia, akinesia and/or tremor and to regulate in such a way the drug input. Such a chip-controlled iontophoretic system would be the first closed-loop system monitoring not pharmacokinetic data (blood levels) but more importantly externally measurable pharmacodynamic effects of Parkinson's disease. This scenario is more feasible as skin irritation and toxicity studies have proven that iontophoresis is a safe route of treatment. This review describes the basics of iontophoresis and the development of a transdermal iontophoretic delivery system on the basis of integrated pharmacokinetic/pharmacodynamic (PK/PD) investigations in patients with idiopathic Parkinson's disease. Transdermal iontophoretic transport of apomorphine was studied both in vitro with human stratum corneum using a newly developed iontophoretic continuous flow-through transport cell and in vivo in a first exploratory study in patients with Parkinson's disease. These studies showed that the delivery of apomorphine is feasible and furthermore the rate of delivery can be controlled by variation of the current densities. Additionally the pretreatment of the skin either with a mono-surfactant or a vesicular suspension of elastic liquid-state vesicles may be useful to further increase the apomorphine flux across the skin in combination with iontophoresis.     

多肽透皮给药研究进展

针对近年来多种多肽类药物的透皮给药系统进行综述。通过查阅国内外多种相关期刊文献。将多肽类药物透皮给药方法分为化学促渗剂、多种物理促渗技术,以及透皮肽、微针技术并对其进行论述。反向离子导入技术应用前景广阔,微针给药系统研究逐步深入,出现了胰岛素智能化微针给药系统,透皮肽的研究发展迅速,相信未来多种蛋白质及多肽的透皮给药方式将应用于临床,极大地促进医疗事业的发展。