Transdermal delivery of proteins using a combination of iontophoresis and microporation.

AIM: This study aimed to investigate transdermal delivery of proteins using combination of microporation and iontophoresis (ITP). Materials & methods & results: Delivery of model protein, Alexa Fluor 555 bovine serum albumin conjugate (AF-BSA) using ITP alone, microneedle (MN) alone, and ITP plus MN combination was assessed using confocal microscopy. Compared to MN alone, combination of MN plus ITP significantly increased skin's penetration depth of AF-BSA (300 vs 110 µm) and achieved lateral distribution of the model protein. Average fluorescence intensity quantified around each microchannel was 23.7-fold (8.2-fold, in vivo) higher for combination treatment compared with MN alone, in vitro. After 1 h in vitro permeation study, the unlabeled BSA amount delivered across skin was found to be 0, 1.4, 0.63 and 14 µg by passive, MN alone, ITP alone and ITP plus MN combination delivery, respectively.

Evaluation of acyclovir cream and gel formulations for transdermal iontophoretic delivery.

BACKGROUND: Efficient iontophoretic transdermal delivery of hydrophilic drug molecules requires selection of appropriate aqueous formulation. In this study, oil/water cream and gel formulations were investigated for iontophoretic transdermal delivery of acyclovir (ACV), a model hydrophilic small-drug molecule, across hairless rat skin on Franz diffusion cells. RESULTS: Iontophoresis (0.2 mA/cm2) enhanced ACV delivery from both 5% cream (pH 6.8) and 4% gel (pH II) formulations. However, sixfold higher drug levels were delivered across the skin using gel formulation (12.25 +/- 4.04 microg/cm2) as compared with cream formulation (2.03 +/- 0.05 microg/cm2). Significantly higher drug levels were delivered when iontophoresis was performed at higher current density (0.32 mA/cm2; p < 0.05). Influence of formulation co-solvents (glycerin and propylene glycol) on drug delivery was also investigated in vitro using Franz cells and in vivo in hairless rats using microdialysis. CONCLUSION: Iontophoretic transdermal delivery of ACV was feasible and dependent on the selection of formulation components and delivery parameters.

Acyclovir skin depot characterization following in vivo iontophoretic delivery.

BACKGROUND/PURPOSE: Current Herpes labialis infection treatment by oral, parenteral or topical routes is inefficient. The objective of this study was to investigate the use of iontophoresis for improved topical delivery of acyclovir (ACV) in vivo in hairless rat. METHODS: Iontophoresis was performed for 10 min using a 5% ACV gel formulation. Tape stripping and skin extractions were performed at different time points following treatment for drug quantification in stratum corneum (SC) and underlying skin, respectively. RESULTS: Fourfold more ACV was detected in the SC immediately following 10-min iontophoresis as compared with passive delivery. Similarly, high ACV levels (29.27±3.52 µg/cm(2)) were achieved in the underlying skin following a single 10-min iontophoretic treatment while no drug detected following passive delivery (P<0.05). At 24-h post-iontophoresis, ACV levels in the SC decreased with a corresponding increase in the underlying skin due to drug migration. After 24-h post-iontophoresis, drug levels gradually decreased in both skin compartments until no ACV was detected at 72-h post-iontophoresis. CONCLUSION: Iontophoretic delivery of ACV resulted in high drug levels in skin layers to form a drug depot, which persisted over 2-3 days.

Iontophoretic delivery of acyclovir: intradermal drug monitoring using microdialysis and quantification by skin extraction.

The objective of this study was to investigate the effect of iontophoresis on the intradermal and transdermal delivery of acyclovir using hairless rat skin on a vertical Franz diffusion cell. In this study, cathodal iontophoretic delivery of acyclovir from a pH 11 formulation was explored. The effects of time of iontophoresis (10 min, 1 h, and 4 h) and current density (0.2, 0.3, and 0.5 mA/cm(2)) on skin permeation were examined. In vitro dermal microdialysis was performed to identify the drug depot formed in the dermis during iontophoresis. Acyclovir delivery into the receptor compartment was not influenced by current density or duration of current application. However, greater drug levels were delivered into the skin as a function of time of current application to form a drug depot. These results were further confirmed by in vitro dermal microdialysis in which higher drug levels were observed in dialysate in the 4 h iontophoresis group due to higher drug levels delivered into the skin layers as compared to 1 h iontophoresis group. Short duration iontophoresis enhanced acyclovir delivery into the skin layers rapidly and thus may be beneficial to improve treatment for cold sores (herpes labialis infection). Microdialysis could be used as a tool to simultaneously monitor drug levels in the tissue's interstitial fluid in real time in an in vitro setting. LAY ABSTRACT: The objective of this study was to investigate the effect of current on the delivery of acyclovir into and across the skin using hairless rat skin mounted on glass diffusion cells. Acyclovir was delivered under negative polarity from a formulation with a very basic pH. The effect of current intensity and duration of application on delivery of acyclovir was investigated. The amount in the skin was also determined by inserting a probe into the skin with a semipermeable membrane that allows sampling of the drug that has entered the skin. When the current intensity or duration was increased, greater drug levels were seen in the skin but not across the skin. It was found that even short duration of current application can deliver acyclovir into the skin and this has potential use for treatment of cold sores.

Iontophoresis mediated in vivo intradermal delivery of terbinafine hydrochloride.

The objective of this study was to investigate the use of iontophoresis for the delivery of terbinafine hydrochloride (TH) into hairless rat skin in vivo. Drug formulation was applied to the abdominal skin and studies were performed using anodal iontophoresis. A current density of 250 microA/cm(2) was applied for 10, 15 and 20 min. Tape stripping and skin extraction were performed thereafter. For depot clearance studies, 20 min treatment was followed by tape stripping and skin extraction at 12, 24 and 48 h. Results indicated that iontophoresis delivered significantly more drug into the deeper skin as compared to controls (p<0.05). Drug levels in the stratum corneum (SC) and underlying skin increased with increasing duration of current application. Depot clearance studies suggested drug depletion within 24 h from SC. A redistribution of terbinafine from the SC to the underlying skin over time was observed. Drug was detectable in the underlying skin for at least 48 h suggesting that formation of a drug depot persisted for at least 2 days following iontophoretic treatment. Thus, iontophoresis of TH may be useful in delivering higher drug levels more rapidly into the superficial and deep seated skin infection sites to form a depot providing sustained release.

Transdermal and intradermal iontophoretic delivery of dexamethasone sodium phosphate: quantification of the drug localized in skin.

In this study, the effect of iontophoresis on the transdermal and intradermal delivery of dexamethasone sodium phosphate (DEX-P) was examined in vitro and in vivo in the hairless rat model by skin permeation studies, tape stripping, and skin extraction. Cathodal or anodal iontophoresis (ITP) was performed and samples were analyzed by HPLC. In vitro experiments revealed that cathodal ITP significantly enhanced the cumulative amount of DEX-P permeating through the skin when compared to passive and anodal delivery. Tape stripping and skin extraction studies performed in vivo after ITP showed enhanced deposition of the drug in the stratum corneum and underlying skin when compared to passive delivery. The DEX-P and DEX depot formed in the stratum corneum and underlying skin were retained for at least 48 h and 24 h, respectively. In conclusion, ITP demonstrated potential as a feasible enhancement technique to drive the drug into and through the skin in significant amounts as compared to passive delivery.

Transdermal iontophoretic delivery of terbinafine hydrochloride: quantitation of drug levels in stratum corneum and underlying skin.

The objective of this study was to determine the effect of iontophoresis on the delivery of terbinafine hydrochloride (4%, w/w) into and across hairless rat skin. In vitro skin uptake and permeation studies were performed using Franz diffusion cells. Anodal iontophoresis was applied for 1h at current densities of 0.2, 0.3 and 0.4mA/cm(2). In addition, iontophoresis was applied for 15, 30, 45 and 60min. Studies were conducted in which the formulation was either removed or left in contact with the skin following iontophoresis and then passive delivery was assessed 23h later. Tape stripping and skin extraction were performed to quantify drug levels in the stratum corneum and the underlying skin, respectively. The samples were analyzed using HPLC. The amount of drug delivered into the stratum corneum following iontophoresis was not significantly different from the amount delivered passively (p>0.05). However, drug levels in the underlying skin were significantly higher for the iontophoretic group. The amount of terbinafine delivered into the skin layers was influenced by current density and duration of current application. Leaving the drug formulation in contact with the skin during the post-iontophoretic period had a significant effect on drug levels delivered into skin layers. Iontophoresis enhanced the delivery of terbinafine hydrochloride into the skin layers and, therefore, may be used to improve the treatment of skin fungal infections.

An ex vivo toe model used to assess applicators for the iontophoretic ungual delivery of terbinafine.

PURPOSE: An ex vivo intact toe model was developed to assess two different applicator designs for iontophoretic delivery of terbinafine into the nail only or the nail and surrounding skin. METHODS: Iontophoretic permeation studies were carried out on intact cadaver toes using nail-only and nail/skin applicators with a current dose of 10 mA*min (0.5 mA for 20 min). RESULTS: Iontophoresis enhanced drug permeation and tissue loading with both applicators tested. Greater drug delivery was observed with the nail/skin applicator due to the additional terbinafine being delivered directly through the lower impedance skin area surrounding the nail. The concentration of drug loaded into the contact area of the nail with the nail-only and nail/skin applicator was ~13 and ~7 fold higher than their respective passive delivery levels but equivalent from each other in total drug mass delivered over the whole nail plate. In vitro release of drug from the iontophoretically loaded nails into agar suggests that a single treatment could have a prolonged effect (>50 days). CONCLUSIONS: This study demonstrates that the ex vivo toe model was useful in assessing the functionality of the different applicator designs. These results suggest that iontophoresis can significantly enhance the delivery of drugs to both the hard and soft tissues of the toe for the treatment of onychomycosis and other nail disorders.

Alteration of the diffusional barrier property of the nail leads to greater terbinafine drug loading and permeation.

The diffusional barrier property of biological systems varies with ultrastructural organization of the tissues and/or cells, and often plays an important role in drug delivery. The nail plate is a thick, hard and impermeable membrane which makes topical nail drug delivery challenging. The current study investigated the effect of physical and chemical alteration of the nail on the trans-ungual drug delivery of terbinafine hydrochloride (TH) under both passive and iontophoretic conditions. Physical alterations were carried out by dorsal or ventral nail layer abrasion, while chemical alterations were performed by defatting or keratolysis or ionto-keratolysis of the nails. Terbinafine permeation into and across the nail plate following various nail treatments showed similar trends in both passive and iontophoretic delivery, although the extent of drug delivery varied with treatment. Application of iontophoresis to the abraded nails significantly improved (P<0.05) TH permeation and loading compared to abraded nails without iontophoresis or normal nails with iontophoresis. Drug permeation was not enhanced when the nail plate was defatted. Keratolysis moderately enhanced the permeation but not the drug load. Ionto-keratolysis enhanced TH permeation and drug load significantly (P<0.05) during passive and iontophoretic delivery as compared to untreated nails. Ionto-keratolysis may be more efficient in permeabilization of nail plates than long term exposure to keratolysing agents.

Ungual and trans-ungual iontophoretic delivery of terbinafine for the treatment of onychomycosis.

The application of iontophoresis was demonstrated in the nail drug delivery of terbinafine (TH) recently. This study explored a systematic assessment of this approach to enhance the drug delivery using a novel topical formulation, and the subsequent release of TH from the drug loaded nails. For the first time, a nail on-agar plate model was used to study the release of drug from the iontophoresis (0.5 mA/cm(2)) loaded nails. In addition, the activity of the drug released from the drug loaded nail plate was studied against Trichophyton rubrum. An increase in applied current density and current duration enhanced the transport of TH into and through the nail plate. In vitro release of drug from the iontophoretic loaded nails into agar plates exhibited 2-phase release pattern. The amount of drug released in both of the in vitro models was comparable, and the nails loaded using iontophoresis continued to release levels of TH > 2 orders of magnitude above the minimum inhibitory concentration over at least 52 days. Results indicate that iontophoresis enhances the delivery of terbinafine into and through the nail plate and suggest that the use of this treatment approach could result in a safe and more efficacious outcome with less frequent treatments.

Trans-ungual iontophoretic delivery of terbinafine.

Successful treatment of deep-seated nail infections remains elusive as the delivery of efficacious levels of antifungal drug to the site of action is very difficult. The aim of the present study was to attain rapid trans-ungual delivery of an antifungal agent, terbinafine, via the topical route using iontophoresis. Initial studies revealed that application of current (0.5 mA/cm(2)) could significantly enhance the trans-ungual delivery of terbinafine. An increase in the applied current or duration of current application enhanced the trans-ungual delivery of terbinafine. Permeation of terbinafine through the nail and drug load in the nail correlated well with the applied electrical dose. Release of drug from nails loaded using iontophoresis followed a two-phase release profile. Light microscopy studies substantiated the capability of iontophoresis to drive a charged molecule across the nail plate. The results of these studies indicate that iontophoresis could be developed as a potential technique for onychomycosis therapy.

Optimization of iontophoretic parameters for the transdermal delivery of methotrexate.

The aim of this work was to study the in vitro factors affecting transdermal iontophoretic delivery of methotrexate across hairless rat skin. Initial screening studies evaluated the effect of ionic strength and donor concentration. A response surface model using factorial design shows an increase in the cumulative amount of methotrexate delivered (Y1) with an increase in current density (X1) and time of application (X2). However, 10 min iontophoresis and 0.05 mA/cm2 current density did not show an increase in delivery with an increase in current density or time of application, respectively. The factorial design was able to identify the optimal parameters that would have been difficult to predict with a conventional one at a time-experimental approach.

Synergistic effect of iontophoresis and soluble microneedles for transdermal delivery of methotrexate.

The aim of this study was to investigate the transdermal iontophoretic delivery of methotrexate, alone or in combination with microneedles, in-vitro and in-vivo using intracutaneous microdialysis in the hairless rat. The average depth of the microdialysis probe in the skin was found to be 0.54 mm. Methotrexate was stable in the presence of an applied electric field as determined by cyclic voltammetry. A current density of 0.4 mA cm(-2) applied for 60 min was used in combination with maltose microneedles to enhance delivery of methotrexate across the skin. Delivery was enhanced by iontophoresis and microneedles, both in-vitro and in-vivo. A synergistic 25-fold enhancement of delivery was observed in-vivo when a combination of microneedles and ionto- phoresis was used compared with either modality alone.