Iontophoretic delivery of drugs: Fundamentals, developments and biomedical applications

Applications and recent advances in transdermal drug delivery systems for the treatment of rheumatoid arthritis

Rheumatoid arthritis is a chronic, systemic autoimmune disease predominantly based on joint lesions with an extremely high disability and deformity rate. Several drugs have been used for the treatment of rheumatoid arthritis, but their use is limited by suboptimal bioavailability, serious adverse effects, and nonnegligible first-pass effects. In contrast, transdermal drug delivery systems (TDDSs) can avoid these drawbacks and improve patient compliance, making them a promising option for the treatment of rheumatoid arthritis (RA). Of course, TDDSs also face unique challenges, as the physiological barrier of the skin makes drug delivery somewhat limited. To overcome this barrier and maximize drug delivery efficiency, TDDSs have evolved in terms of the principle of transdermal facilitation and transdermal facilitation technology, and different generations of TDDSs have been derived, which have significantly improved transdermal efficiency and even achieved individualized controlled drug delivery. In this review, we summarize the different generations of transdermal drug delivery systems, the corresponding transdermal strategies, and their applications in the treatment of RA.

Portable Iontophoresis Device for Efficient Drug Delivery

The timely delivery of drugs to specific locations in the body is imperative to ensure the efficacy of treatment. This study introduces a portable facial device that can deliver drugs efficiently using iontophoresis. Two types of power supplies-direct current and pulse ionization supplies-were manufactured by injection molding. Electrical stimulation elements, which contained Ag metal wires, were woven into facial mask packs. The diffusion phenomenon in the skin and iontophoresis were numerically modeled. Injection molding was simulated before the device was manufactured. Analysis using rhodamine B demonstrated a remarkable increase in the moisture content of the skin and effective absorption of the drug under an applied electric field upon the application of iontophoresis. The proposed concept and design constitute a new method of achieving effective drug absorption with wearable devices.

Electromotive Enhanced Drug Administration in Oncology: Principles, Evidence, Current and Emerging Applications

Local-regional administration of cytotoxic drugs is an important adjunct to systemic chemotherapy amongst cancer patients. It allows for targeted delivery of agents at high concentration to target sites while minimizing systemic side effects. Despite the pharmacokinetic advantages of the local-regional approach, drug transport into tumor nodules remains limited due to the biophysical properties of these tissues. Electromotive enhanced drug administration (EMDA) represents a potential solution to overcome challenges in local drug transport by applying electric currents. Through electrokinetic phenomena of electromigration, electroosmosis and electroporation, electric currents have been shown to improve drug penetration and distribution in a wide variety of clinical applications. Amongst patients with non-muscular invasive bladder cancer (NMIBC) and basal and squamous cell skin cancers, EMDA has been successfully adopted and proven efficacious in several pre-clinical and clinical studies. Its application in ophthalmological and other conditions has also been explored. This review provides an overview of the underlying principles and factors that govern EMDA and discusses its application in cancer patients. We also discuss novel EMDA approaches in pre-clinical studies and explore future opportunities of developments in this field.

Noninvasive transdermal delivery of liposomes by weak electric current

Noninvasive transdermal drug delivery (NTDD) offers an exciting new method of administration relative to conventional routes, but is associated with some challenges. Liposomes are capable of encapsulating transdermally-unfavorable drugs. However, the horny layer of skin is a significant barrier that limits efficient transdermal delivery of liposomes. Iontophoresis using weak electric current (WEC) represents a NTDD technology. WEC treatment of liposomes applied to the skin surface improves transdermal penetration of encapsulated drugs by cooperative effects. In this review, we provide an overview of the application of WEC/liposomes for transdermal delivery of macromolecules and low molecular weight drugs. We compare the transdermal delivery and therapeutic efficiency of the combined system with conventional routes of administration and their individual use. We discuss a novel perspective on the mechanism of WEC-mediated transdermal delivery of liposomes, which suggests that WEC activates the intracellular signaling pathway for transdermal permeation and induces unique endocytosis in skin cells.

Internet-of-Things-Enabled Dual-Channel Iontophoretic Drug Delivery System for Elderly Patient Medication Management

Wireless controllers have found its application in the supervision of the patients in the hospitals. It is not only a valid issue for the developing countries but also for the developed countries. For this reason, scientists are working on the advancement of medical devices that are capable of decreasing the workload of health caregivers. In this study, the development of an iontophoretic drug delivery device that could be controlled using a mobile is described. For the purpose, hardware and a software module were developed. The hardware module consisted of a two-channel voltage-controlled constant current sources that were used for driving the iontophoretic device. A mobile app was developed to control the two-channel iontophoretic device and to monitor the loose lead of the active and the passive patches. In the case of detection of the loose lead, the specific iontophoretic channel was stopped. Further, the audio-visual indicator was developed for the detection of the detachment of the patches (loose lead). The device was tested in vitro by performing the drug release study using drug-loaded emulsion gels that were formulated.

Advances in transdermal insulin delivery

Insulin therapy is necessary to regulate blood glucose levels for people with type 1 diabetes and commonly used in advanced type 2 diabetes. Although subcutaneous insulin administration via hypodermic injection or pump-mediated infusion is the standard route of insulin delivery, it may be associated with pain, needle phobia, and decreased adherence, as well as the risk of infection. Therefore, transdermal insulin delivery has been widely investigated as an attractive alternative to subcutaneous approaches for diabetes management in recent years. Transdermal systems designed to prevent insulin degradation and offer controlled, sustained release of insulin may be desirable for patients and lead to increased adherence and glycemic outcomes. A challenge for transdermal insulin delivery is the inefficient passive insulin absorption through the skin due to the large molecular weight of the protein drug. In this review, we focus on the different transdermal insulin delivery techniques and their respective advantages and limitations, including chemical enhancers-promoted, electrically enhanced, mechanical force-triggered, and microneedle-assisted methods.

Simultaneous Monitoring of Sweat and Interstitial Fluid Using a Single Wearable Biosensor Platform

The development of wearable biosensors for continuous noninvasive monitoring of target biomarkers is limited to assays of a single sampled biofluid. An example of simultaneous noninvasive sampling and analysis of two different biofluids using a single wearable epidermal platform is demonstrated here. The concept is successfully realized through sweat stimulation (via transdermal pilocarpine delivery) at an anode, alongside extraction of interstitial fluid (ISF) at a cathode. The system thus allows on-demand, controlled sampling of the two epidermal biofluids at the same time, at two physically separate locations (on the same flexible platform) containing different electrochemical biosensors for monitoring the corresponding biomarkers. Such a dual biofluid sampling and analysis concept is implemented using a cost-effective screen-printing technique with body-compliant temporary tattoo materials and conformal wireless readout circuits to enable real-time measurement of biomarkers in the sampled epidermal biofluids. The performance of the developed wearable device is demonstrated by measuring sweat-alcohol and ISF-glucose in human subjects consuming food and alcoholic drinks. The different compositions of sweat and ISF with good correlations of their chemical constituents to their blood levels make the developed platform extremely attractive for enhancing the power and scope of next-generation noninvasive epidermal biosensing systems.

Evaluation of continuous constant current and continuous pulsed current in sweat induction for cystic fibrosis diagnosis

Background

The sweat test (ST) is the gold standard for the diagnosis of cystic fibrosis (CF). However, little is known about sweat induction using different types of currents and waves. In this context, our objective was to develop a device to induce sweat and compare the use of continuous constant current (CCC) and continuous pulsed current (CPC) in individuals with CF and healthy controls.

Methods

A prospective cross-sectional study with experimental intervention. The variables of gender, ethnicity, age, and body mass index (BMI) were considered. The method of Gibson and Cooke was used, and the following markers were evaluated: sweat weight, electrical impedance, sufficient sweat amount, and CF diagnosis. Triangular (TPC) or sinusoidal (SPC) pulsed current was applied to the right arm, and CCC was applied to the left arm.

Results

The study analyzed 260 individuals, 141/213 (54.2%) were female participants, 135/260 (51.9%) were Caucasians. The distribution of individuals by concentration of chloride at the ST was: (CF) 26/260 (10%); (borderlines) 109/260 (41.9%); (healthy) 97/260 (37.3%); (insufficient weight in sweat) 28/260 (10.8%). No association was observed between the sufficient sweat amount to perform the ST when we compared the currents. However, the SPC showed a higher amount of sweat weight. Using Bland and Altman plot considering the agreement between the sweat chloride values achieved from CPC [SPC and TPC] and CCC, there was no proportional bias and mean values are unrelated and only explain less than 8% of the variation. Moreover, TPC presented higher electrical impedance when compared with SPC and CCC. SPC presented lower electrical impedance and higher sweat weight than CCC. Male participants presented lower electrical impedance and higher sweat weight with CCC and TPC, and higher sweat weight with SPC.

Conclusions

The evaluated currents are safe and able to induce and produce sweat in sufficient quantities for the ST. SPC presented lower electrical impedance when compared with other currents. The use of SPC is recommended to induce sweat in patients with sweat problems. Finally, ethnicity, gender, age and BMI did not influence sweat induction at the ST, and no side effect was observed in our study.

Electronic supplementary material

The online version of this article (10.1186/s12890-018-0696-3) contains supplementary material, which is available to authorized users.

Effective permeation of 2.5 and 5% lidocaine hydrochloride in human skin using iontophoresis technique

BACKGROUND

Lidocaine Hydrochloride (HCL) is one of the commonest topical local anesthetic drugs. The permeation of the lidocaine can be enhanced by iontophoresis (IOP). The purpose of this study was to evaluate the permeability of 2.5 and 5% lidocaine permeation in ex vivo human skin using different IOP waveform.

METHODS

Continuous and modulated IOP at the current density of 0.5 mA/cm² were applied across human skin (n = 3) in donor chamber of vertical diffusion cell at 2.5 and 5% lidocaine concentration. High Performance Liquid Chromatography was used to determine lidocaine concentration.

RESULTS

Findings revealed that lidocaine concentration increased effectively in a time-dependent manner in both modulated and continuous IOP at 2.5 and 5% lidocaine concentration. Compared to the passive group, the flux of lidocaine with modulated and continuous IOP were higher of about six and ten-fold, respectively. However, no significant difference was observed between continuous and modulated IOP groups at both lidocaine concentrations. At 2.5% lidocaine concentration, the permeation time taken by modulated and continuous IOP to attain therapeutic levels of 142 and 164 μg/cm₂ , respectively, was approximately 10 minutes. At 5% lidocaine, the therapeutic permeation of 129 and 147 μg/cm₂ , respectively, was achieved at approximately 5 minutes after applying iontophoresis waveform.

CONCLUSION

Study shows that modulated IOP can be a promising alternative method in clinical settings aside from continuous IOP. Based on the clinical requirements, IOP can be used at 2.5 and 5% lidocaine concentration depending on need of relatively short or very short onset action.

Prolonged and localized sweat stimulation by iontophoretic delivery of the slowly-metabolized cholinergic agent carbachol

BACKGROUND

Continuous non-invasive sampling and sensing of multiple classes of analytes could revolutionize medical diagnostics and wearable technologies, but also remains highly elusive because of the many confounding factors for candidate biofluids such as interstitial fluid, tears, saliva, and sweat. Eccrine sweat biosensing has seen a recent surge in demonstrations of wearable sampling and sensing devices. However, for subjects at rest, access to eccrine sweat is highly limited and unpredictable compared to saliva and tears.

OBJECTIVE

Reported here is a prolonged and localized sweat stimulation by iontophoretic delivery of the slowly-metabolized nicotinic cholinergic agonist carbachol.

METHODS

Presented here are detailed measurements of natural baseline sweat rates across multiple days, confirming a clear need for localized sweat stimulation. Iontophoresis was performed with either carbachol or pilocarpine in order to stimulate sweat in subjects at rest. Furthermore, improved methods of quantifying sweat generation rates (nL/min/gland) are demonstrated.

RESULTS

In-vivo testing reveals that carbachol stimulation can surpass a major goal of 24-h sweat access, in some cases providing more than an order of magnitude longer duration than stimulation with commonly-used pilocarpine. Also demonstrated is reduction of the traditional iontophoretic dosage for sweat stimulation (<5.25-42mC/cm²). This increases the viability of repeated dosing as demonstrated herein, and for carbachol is as much as 100-1000X less than used for other applications.

CONCLUSION

This work is not only significant for wearable sweat biosensing technology, but could also have broader impact for those studying topical skin products, antiperspirants, textiles and medical adhesives, nerve disorders, the effects of perspiration on skin-health, skin related diseases such as idiopathic pure sudomotor failure and hyperhidrosis, and other skin- and perspiration-related applications.

Effect of terpenes on transdermal iontophoretic delivery of diclofenac potassium under constant voltage

OBJECTIVE

The aim of the study was to enhance the transdermal delivery of diclofenac potassium (DP) from hydrogels by constant voltage iontophoresis (CVI). The other objective was to establish the safety and efficacy of CVI in rats.

MATERIALS AND METHODS

Hydrogels of DP were developed using hydroxyethyl cellulose as matrix material and geraniol, l-menthol and thymol as iontophoretic efficiency enhancers (IEE). In vitro permeation of hydrogels under CVI (1.5 V) was performed in Franz diffusion cells across porcine skin. The ability of CVI to deliver therapeutic amount of DP in vivo was assessed in rat paw edema model.

RESULTS

CVI significantly (p < 0.05) increased the steady state flux of DP compared to the passive. The hydrogels containing geraniol and l-menthol enhanced the iontophoretic flux of DP by ∼4.75 and ∼4.49 fold, respectively compared to passive control. The in vivo studies indicated that CVI in combination with IEE, significantly reduced (p < 0.05) area under the curve (AUC) of % inflammation compared to passive treatment. An excellent correlation (r = 0.996) was noted between in vitro flux values and AUC of % inflammation.

CONCLUSION

The preclinical studies conclusively demonstrated that CVI in combination with IEE's such as geraniol or l-menthol has the potential to safely deliver therapeutic amounts of DP.

Integrated sudomotor axon reflex sweat stimulation for continuous sweat analyte analysis with individuals at rest

Eccrine sweat has rapidly emerged as a non-invasive, ergonomic, and rich source of chemical analytes with numerous technological demonstrations now showing the ability for continuous electrochemical sensing. However, beyond active perspirers (athletes, workers, etc.), continuous sweat access in individuals at rest has hindered the advancement of both sweat sensing science and technology. Reported here is integration of sudomotor axon reflex sweat stimulation for continuous wearable sweat analyte analysis, including the ability for side-by-side integration of chemical stimulants & sensors without cross-contamination. This integration approach is uniquely compatible with sensors which consume the analyte (enzymatic) or sensors which equilibrate with analyte concentrations. In vivo validation is performed using iontophoretic delivery of carbachol with ion-selective and impedance sensors for sweat analysis. Carbachol has shown prolonged sweat stimulation in directly stimulated regions for five hours or longer. This work represents a significant leap forward in sweat sensing technology, and may be of broader interest to those interested in on-skin sensing integrated with drug-delivery.

Surging footprints of mathematical modeling for prediction of transdermal permeability

In vivo skin permeation studies are considered gold standard but are difficult to perform and evaluate due to ethical issues and complexity of process involved. In recent past, a useful tool has been developed by combining the computational modeling and experimental data for expounding biological complexity. Modeling of percutaneous permeation studies provides an ethical and viable alternative to laboratory experimentation. Scientists are exploring complex models in magnificent details with advancement in computational power and technology. Mathematical models of skin permeability are highly relevant with respect to transdermal drug delivery, assessment of dermal exposure to industrial and environmental hazards as well as in developing fundamental understanding of biotransport processes. Present review focuses on various mathematical models developed till now for the transdermal drug delivery along with their applications.

Intravesical electro-osmotic administration of mitomycin C

Bladder cancer is very common and most cases are diagnosed as nonmuscle invasive disease, which is characterized by its propensity to recur and progress. Intravesical therapy is used to delay recurrence and progression, while cystectomy is reserved for patients who are refractory to transurethral resection and intravesical therapy. There is an increasing interest in methods to enhance the delivery of intravesical chemotherapeutic agents to improve efficacy. In vitro and in vivo studies demonstrated that electro-osmosis of mitomycin C (MMC) is more effective in delivering this drug into the urothelium, lamina propria, and superficial muscle layers of the bladder wall than is passive transport. Higher MMC tissue concentrations might have a clinical impact in the treatment of nonmuscle invasive bladder cancer (NMIBC). In randomized trials, intravesical electro-osmotic MMC was associated with superior response rate in high-risk NMIBC cancer, compared with passive diffusion MMC transport. New strategies such as intravesical Bacillus Calmette-Guerin (BCG) combined with electro-osmotic MMC as well as intravesical pre-operative electro-osmotic MMC provided promising results in terms of higher remission rates and longer remission times.Device-assisted intravesical chemotherapy may be a useful ancillary procedure in the treatment of NMIBC. Its evaluation must be planned with respect to the technical functioning of equipment and their use for a clear purpose to avoid the financial and human costs associated with incorrect therapies.

Optimization of ultrasound induced emulsification on the formulation of palm-olein based nanoemulsions for the incorporation of antioxidant β-D-glucan polysaccharides

Polysaccharides of β-D-glucan configuration have well-known antioxidant activity against reactive free radicals generated from the oxidation of metabolic processes. In this study, β-D-glucan-polysaccharides extracted from Ganoderma lucidum were incorporated in palm olein based nanoemulsions which act as carrier systems to enhance the delivery and bioactivity of these polysaccharides and could be potentially useful for skin care applications. Initially response surface statistical design (Central Composite Design--CCD) was subjected to optimize the formulation variables of oil-in-water (O/W) nanoemulsions induced by ultrasound. The optimal formulation variables as predicted by CCD resulted in considerably improving the physical characteristics of ultrasonically formulated nanoemulsions by minimizing their droplet size, polydispersity index and viscosity. Moreover, the β-D-glucan-loaded nanoemulsions exhibited good stability over 90 days under different storage conditions (4 °C and 25 °C). The studies using palm olein based β-D-glucan-loaded nanoemulsion generated using ultrasound confirm higher antioxidant activity as compared to free β-D-glucan.

Effect of gel properties on transdermal iontophoretic delivery of diclofenac sodium

The aim of the study was to develop hydrogels and investigate the suitability for transdermal delivery of diclofenac sodium (DS) using constant voltage iontophoresis (CVI). Four batches of hydrogels of DS were developed using hydroxylethyl cellulose (HEC) as matrix material and terpenes as penetration enhancers. The hydrogels displayed a viscosity of ~1500 cps at a shear rate of 250 s-1 that was unlikely to change on minute shift in pH or temperature so that the iontophoretic transport would be unaffected. Moreover, the hydrogels were found to possess adequate conductivity at pH 7.4 to enable iontophoretic delivery of DS. In vitro studies indicated that passive transport of DS across porcine skin from hydrogels was comparable (p>0.05) to aqueous solution. The lead hydrogel (F1), containing geraniol was found to enhance the iontophoretic flux of DS by 5.16 fold at 1.5 V compared to passive control. In vivo studies in rats indicated that CVI on application of F1 significantly suppressed (p<0.001) carrageenan induced edema compared to passive treatment throughout the study.

Pulsed direct and constant direct currents in the pilocarpine iontophoresis sweat chloride test

Background

The classic sweat test (CST) is the golden standard for cystic fibrosis (CF) diagnosis. Then, our aim was compare the production and volume of sweat, and side effects caused by pulsed direct current (PDC) and constant direct current (CDC). To determine the optimal stimulation time (ST) for the sweat collection. To verify the PDC as CF diagnosis option.

Methods

Prospective study with cross-sectional experimental intervention. Experiment 1 (right arm): PDC and CDC. ST at 10 min and sweat collected at 30 min. Currents of 0.5; 0.75; 1.0 and 1.5 mA and frequencies of 0, 200, 1,000 and 5,000 Hz applied. Experiment 2 (left arm): current of 1.0 mA, ST at 5 and 10 min and sweat collected at 15 and 30 min with frequencies of 0; 200; 1,000 and 5,000 Hz applied Experiments 1 and 2 were performed with current density (CD) from 0.07 to 0.21 mA/cm². Experiment 3: PDC was used in typical CF patients with two CFTR mutations screened and or with CF diagnosis by rectal biopsy and patients with atypical CF.

Results

48 subjects (79.16% female) with average of 29.54 ± 8.87 years old were enrolled. There was no statistical difference between the interaction of frequency and current in the sweat weight (p = 0.7488). Individually, positive association was achieved between weight sweat and stimulation frequency (p = 0.0088); and current (p = 0.0025). The sweat production was higher for 10 min of stimulation (p = 0.0023). The sweat collection was better for 30 min (p = 0.0019). The skin impedance was not influenced by ST and sweat collection (p > 0.05). The current frequency was inversely associated with the skin impedance (p < 0.0001). The skin temperature measured before stimulation was higher than after (p < 0.0001). In Experiment 3 (29 subjects) the PDC showed better kappa index compared to CDC (0.9218 versus 0.5205, respectively).

Conclusions

The performance of the CST with CDC and PDC with CD of 0.14 to 0.21 mA/cm² showed efficacy in steps of stimulation and collection of sweat, without side effects. The optimal stimulation time and sweat collection were, respectively, 10 and 30 min.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2466-14-198) contains supplementary material, which is available to authorized users.

Effects of non-Newtonian power law rheology on mass transport of a neutral solute for electro-osmotic flow in a porous microtube

Mass transport of a neutral solute for a power law fluid in a porous microtube under electro-osmotic flow regime is characterized in this study. Combined electro-osmotic and pressure driven flow is conducted herein. An analytical solution of concentration profile within mass transfer boundary layer is derived from the first principle. The solute transport through the porous wall is also coupled with the electro-osmotic flow to predict the solute concentration in the permeate stream. The effects of non-Newtonian rheology and the operating conditions on the permeation rate and permeate solute concentration are analyzed in detail. Both cases of assisting (electro-osmotic and poiseulle flow are in same direction) and opposing flow (the individual flows are in opposite direction) cases are taken care of. Enhancement of Sherwood due to electro-osmotic flow for a non-porous conduit is also quantified. Effects if non-Newtonian rheology on Sherwood number enhancement are observed.

Potential use of iontophoresis for transdermal delivery of NF-kappaB decoy oligonucleotides

Topical application of nuclear factor-kappaB (NF-kappaB) decoy appears to provide a novel therapeutic potency in the treatment of inflammation and atopic dermatitis. However, it is difficult to deliver NF-kappaB decoy oligonucleotides (ODN) into the skin by conventional methods based on passive diffusion because of its hydrophilicity and high molecular weight. In this study, we evaluated the in vitro transdermal delivery of fluorescein isothiocyanate (FITC)-NF-kappaB decoy ODN using a pulse depolarization (PDP) iontophoresis. In vitro iontophoretic experiments were performed on isolated C57BL/6 mice skin using a horizontal diffusion cell. The apparent flux values of FITC-NF-kappaB decoy ODN were enhanced with increasing the current density and NF-kappaB decoy ODN concentration by iontophoresis. Accumulation of FITC-NF-kappaB decoy ODN was observed at the epidermis and upper dermis by iontophoresis. In mouse model of skin inflammation, iontophoretic delivery of NF-kappaB decoy ODN significantly reduced the increase in ear thickness caused by phorbol ester as well as the protein and mRNA expression levels of tumor necrosis factor-alpha (TNF-alpha) in the mice ears. These results suggest that iontophoresis is a useful and promising enhancement technique for transdermal delivery of NF-kappaB decoy ODN.

Current concepts in assessment of microvascular endothelial function using laser Doppler imaging and iontophoresis

Effective evaluation of endothelial function is a powerful tool for determining patients at risk of development and progression of cardiovascular disease. As an alternative to invasive tests of endothelial function, several noninvasive methods have been developed, including the use of laser Doppler flowmetry/imaging to measure cutaneous perfusion accompanied by iontophoresis of acetylcholine and sodium nitroprusside. It is clear from previous studies that this technique provides an easy, validated, and reproducible method for investigators to assess and monitor endothelial function in patients with a variety of pathologic conditions, but it may also be used to examine disease progression over time and responsiveness to treatment, thereby facilitating clinical trials. However, a standardization of protocols would help reduce the apparent controversy seen in the literature. With its increasing use by other groups, it is anticipated that further published studies will help to provide a better understanding of the development and progression of cardiovascular disease.

Iontophoretic Enhancement of Timolol across Human Dermatomed SkinIn Vitro

The objective of this study was to assess the in vitro the iontophoretic delivery of Timolol across human dermatomed skin in order to determine whether therapeutic doses of this drug can be delivered. Anodal iontophoresis of Timolol was performed by manipulating the donor vehicle and the current density. It was observed that by reducing simultaneously the competitive ions (NaCl) from 8 to 4 g/l and the pH from 7.4 to 4.7, the iontophoretic flux was significantly increased by a factor of 1.5 (669+/-81 microg/cm h). In order to simulate the situation in a transdermal patch, the iontophoretic delivery of Timolol was also studied after adding an artificial porous membrane placed between the Timolol formulation and the human dermatomed skin. No significant difference was observed in the steady state flux across the skin when an artificial membrane was added. Furthermore, a linear relationship was found between current density and steady state flux. These results indicate that the iontophoretic delivery of Timolol can be accurately controlled by the applied current. Assuming a one to one in vitro/in vivo correlation the Timolol transport in vitro results in therapeutic plasma concentrations in humans with very low current densities limiting possible skin irritation.

Iontophoretic transport across a multiple membrane system

The objective of the present study was to investigate the iontophoretic transport behavior across multiple membranes of different barrier properties. Spectra/Por(R) (SP) and Ionac membranes were the synthetic membranes and sclera was the biomembrane in this model study. The barrier properties of SP membranes were determined individually in passive and iontophoresis transport experiments with tetraethylammonium ion (TEA), chloride ion (Cl), and mannitol as the model permeants. Passive and iontophoretic transport experiments were then conducted with an assembly of SP membranes. The contribution of electroosmosis to iontophoresis was assessed using the mannitol data. Model analysis was performed to study the contribution of diffusion and electromigration to electrotransport across the multiple membrane system. The effects of membrane barrier thickness upon ion-exchange membrane-enhanced iontophoresis were examined with Ionac, SP, and sclera. The present study shows that iontophoretic transport of TEA across the membrane system was related to the thicknesses and permeability coefficients of the membranes and the electromobilities of the permeant across the individual membranes in the assembly. Model analysis suggests significant contribution of diffusion within the membranes across the membrane system, and this mechanism is relatively independent of the current density applied across the system in iontophoresis dominant transport.

Enhancement of iontophoretic transport of diphenhydramine hydrochloride thermosensitive gel by optimization of pH, polymer concentration, electrode design, and pulse rate

The purpose of the present study was to explore the passive and electrically assisted transdermal transport of diphenhydramine hydrochloride (DPH) by iontophoresis. For better bioavailability, better patient compliance, and enhanced delivery of DPH, an iontophoretic drug delivery system of a thermosensitive DPH gel was formulated using Lutrol F-127. The study was conducted using silver-silver chloride electrodes across hairless pig skin. The effects of pH, polymer concentration, electrode design, and pulse rate on the DPH permeation were investigated. The relationship between temperature, viscosity, and conductance of DPH was correlated using conductometry. Iontophoretic transport of DPH was found to increase with a decrease in the pH of the medium and an increase in the surface area of the electrode. Viscosity measurements and flux calculations indicated the suitability of the Lutrol gel for transdermal iontophoretic delivery of DPH. Anodal pulsed iontophoresis with disc electrode significantly increased the DPH skin permeation as compared with the passive controls.

Effect of Pressure on Molecular and Ionic Motions in Ultraviscous Acetaminophen–Aspirin Mixture

Effect of pressure and temperature on molecular motions and dc conductivity in ultraviscous, 50 wt% acetaminophen-aspirin melt has been studied by dielectric relaxation spectroscopy. The spectra obtained over the pressure range, 5-300 MPa and temperature range, 295-320 K show a distribution of relaxation times greater than found in pure acetaminophen. The equilibrium dielectric permittivity and relaxation time, tau, of the melt increase with increase in pressure and decrease in temperature and the dc conductivity, sigma(dc), decreases. The pressure and temperature variation of the limiting high frequency permittivity shows significant contribution from infrared polarization. The volumes of activation for sigma(dc) and tau vary with both the pressure and temperature, indicating that there is also a structural effect that determine sigma(dc). This effect would add a non-linear term to the Debye-Stokes-Einstein equation for variation of sigma(dc) with tau. The ultraviscous liquid remains stable with time, and with change in temperature and pressure, suggesting that a more stable glassy state of a pharmaceutical may be obtained by mixing a second component.

Enhanced Transscleral Iontophoretic Transport with Ion-Exchange Membrane

PURPOSE

Transscleral iontophoresis has been recently re-examined for drug delivery to the back of the eye. In conventional iontophoresis, due to the relatively high electromobility of the endogenous competing ions (counterions) relative to that of the drug ion in the tissue barrier, the efficiency of iontophoretic drug delivery is generally low. The objective of the present study was to examine ion-exchange membrane-enhanced transscleral iontophoretic transport in which the ion-exchange membrane in series with the sclera can hinder the transport of the competing counterions and selectively allow the transport of the permeant across the sclera.

METHODS

The physical properties of the Ionac ion-exchange membrane and excised rabbit sclera were determined in equilibrium uptake experiments and in passive and iontophoretic transport experiments with salicylate, tetraethylammonium, urea, and mannitol. Transscleral experiments with the ion-exchange membrane were conducted with salicylate and excised rabbit sclera in vitro. The contribution of electroosmosis to electrotransport during transscleral iontophoresis was assessed with urea and mannitol.

RESULTS

The ion-exchange membrane is highly positively charged and has a small effective pore size. The sclera is relatively porous with a large effective pore size and low pore tortuosity. The sclera is also net negatively charged but this does not significantly affect the transport of small ions. A three-fold steady-state transscleral flux enhancement of salicylate was observed in ion-exchange membrane-enhanced iontophoresis over conventional transscleral iontophoresis without the membrane. Such enhancement was relatively independent of the applied electric current density and the thickness of the studied ion-exchange membrane assembly. Although the ion-exchange membrane altered transscleral electroosmosis, the contribution of electroosmosis to electrotransport was not significant.

CONCLUSIONS

The present study has demonstrated the potential of ion-exchange membranes for enhancing iontophoretic transport and drug delivery.

Visualization studies of human skin in vitro/in vivo under the influence of an electrical field

The aim of this study was to investigate the local changes in the ultrastructure of human skin after iontophoresis, using cryo-scanning, transmission and freeze fracture electron microscopy in human skin in vitro and in vivo. Human dermatomed skin was subjected to passive diffusion for 6 hours followed by nine hours of iontophoresis at 0.5 mA/cm2. The skin was processed and examined using both cryo-scanning electron microscopy (Cryo-SEM) and transmission electron microscopy (TEM). In addition, iontophoresis patches were applied to healthy volunteers for 3.5h with 0.5h of passive delivery followed by 3h of iontophoresis at a current density of 0.25 mA/cm2. Subsequently, a series of tape stripping were performed, which were visualized by freeze fracture transmission electron microscopy (FFTEM). In vitro, the cryo-scanning electron microscopy study revealed that electric current induced changes in the water distribution in the stratum corneum. Transmission electron microscopy showed no local changes in the ultrastructure of the stratum corneum; however, layers of detached corneocytes were frequently observed especially at the anodal site. In vivo, there was no evidence of perturbation of the stratum corneum lipid organization; however, changes in the fracture were noticed deeper in the stratum corneum at the anodal side, indicating a weakening of the desmosomal structure. The in vitro/in vivo studies suggest that iontophoresis results in the formation of intercellular water pools (in vitro observation) and a weakening of the desmosomal structure (in vivo observation) only in the upper part of the stratum corneum. However, no changes in the lipid organization were observed in vitro and in vivo at the current densities of 0.5 and 0.25 mA/cm2, respectively. Therefore, even at relatively high current densities, no drastic changes in the ultrastructure of the stratum corneum are observed. As far as structural changes in stratum corneum are concerned iontophoresis is therefore a safe method at the experimental conditions we used.

Topical iontophoretic administration of acyclovir for the episodic treatment of herpes labialis: a randomized, double-blind, placebo-controlled, clinic-initiated trial

BACKGROUND

Multiple studies of the use of acyclovir for the treatment of herpes labialis have suggested that the nominal efficacy of the topical formulation is the result of inadequate penetration of the drug into the target site of infection, the basal epidermis.

METHODS

We developed a low-voltage, wireless, hand-held, computer-controlled, iontophoretic applicator to enhance the skin penetration of topical acyclovir in the treatment of herpes labialis. We performed a multicenter, placebo-controlled, clinic-initiated, pilot trial of a single, topical, iontophoretic application of 5% acyclovir cream for the episodic treatment of herpes labialis among 200 patients with an incipient cold sore outbreak at the erythema or papular/edema lesion stage.

RESULTS

The median classic lesion healing time (aborted lesions were assigned a value of 0 h) was 1.5 days shorter for the active treatment group than for the vehicle group (113 h vs. 148 h; P = .02). In the subgroup of patients who presented with lesions in the erythema stage, the median classic lesion healing time was 3 days shorter for the acyclovir group, compared with the control group (49 h vs. 120 h; P < .03), and the acyclovir group tended to have more aborted lesions than did the control group (46% vs. 24%; P = .10).

CONCLUSIONS

Single-dose topical iontophoresis of acyclovir appears to be a convenient and effective treatment for cold sores and merits further clinical investigation.

Current Density Imaging and Electrically Induced Skin Burns Under Surface Electrodes

The origin of electrical burns under gel-type surface electrodes is a controversial topic that is not well understood. To investigate the phenomenon, we have developed an excised porcine skin-gel model, and used low-frequency current density imaging (LFCDI) to determine the current density (CD) distribution through the skin before and after burns were induced by application of electrical current (200 Hz, 70% duty cycle, 20-35 mA monophasic square waveform applied to the electrodes for 30-135 min). The regions of increased CD correlate well with the gross morphological changes (burns) observed. The measurement is sensitive enough to show regions of high current densities in the pre-burn skin, that correlate with areas were burn welts were produced, thus predicting areas where burns are likely to occur. Statistics performed on 28 skin patches revealed a charge dependency of the burn areas and a relatively uniform distribution. The results do not support a thermal origin of the burns but rather electro-chemical mechanisms. We found a statistically significant difference between burn area coverage during anodic and cathodic experiments.

Lontophoretic administration of dexamethasone into the tarsocrural joint in horses

OBJECTIVE

To determine whether iontophoretic administration of dexamethasone to horses results in detectable concentrations in synovial fluid, plasma, and urine.

ANIMALS

6 adult mares.

PROCEDURE

Iontophoresis was used to administer dexamethasone. Treatments (4 mA for 20 minutes) were administered to a tarsocrural joint of each mare. The drug electrode contained 3 ml of dexamethasone sodium phosphate at a concentration of 4 or 10 mg/ml. Samples of synovial fluid, blood, and urine were obtained before and 0.5, 4, 8, and 24 hours after each treatment. All samples were tested for dexamethasone using an ELISA. Synovial fluid also was evaluated for dexamethasone, using high-performance liquid chromatography.

RESULTS

The lower and upper limits of detection for dexamethasone in synovial fluid with the ELISA were 0.21 and 1.5 ng/ml, respectively. Dexamethasone administered at a concentration of 10 mg/ml was detected by the ELISA in synovial fluid of 5 mares from 0.5 to 24 hours and in urine of 4 mares from 0.5 to 8 hours after each treatment, but it was not detected in plasma. Mean synovial fluid concentration of dexamethasone was 1.01 ng/ml. Dexamethasone administered at a concentration of 4 mg/ml was detected by the ELISA in urine of 2 mares at 0.5 and 4 hours after treatment, but it was not detected in synovial fluid or plasma.

CONCLUSIONS AND CLINICAL RELEVANCE

Iontophoresis cannot be considered an effective method for delivery of dexamethasone to synovial fluid of horses, because drug concentrations achieved in this study were less than therapeutic concentrations.

Iontophoretic drug delivery using the IOMED Phoresor®system

Iontophoresis, or electromotive drug administration, is a process that enhances the delivery of drugs through a biological membrane via the application of low-intensity electrical current. This technology offers several advantages over oral and injection drug delivery. Key advantages of iontophoretic drug delivery include the avoidance of pain and potential for infection associated with needle injection, the ability to control the rate of drug delivery, the ability to programme the drug-delivery profile and the minimisation of local tissue trauma. Research using iontophoresis has shown delivery of a number of drug classes. By controlling the applied electric current one can tailor a dosage regimen with a drug delivery profile specific for an indication and the needs of the patient. Advances in iontophoretic electrode design, microelectronics and methods to optimise iontophoretic drug delivery have improved the ability to safely deliver both older, off-patent drugs, as well as new chemical entities being developed to treat a variety of diseases. In addition to transdermal applications, current research indicates that iontophoresis may prove to be a viable noninvasive drug delivery method for treating conditions that affect the back of the eye.

Transdermal Iontophoresis of Insulin

The delivery of large peptides through the skin poses a significant challenge, and various strategies are under active investigation for enhancing the transdermal permeation. For large peptides, it is difficult to achieve significant permeation using iontophoresis alone. Hence a combination of fatty acids with iontophoresis was hypothesized to result in higher enhancement than achieved with either of them alone. Saturated fatty acids and cis unsaturated fatty acids were studied in combination with iontophoresis using excised rat skin. The skin was pretreated for 2 h with an ethanolic (EtOH) solution of 5% w/v or v/v fatty acids, namely lauric acid (LA), oleic acid (OA), linoleic acid (LOA) and linolenic acid (LLA), followed by either passive or iontophoretic permeation (0.5 mA/cm2 for 6 h). Fourier transform infrared spectroscopy (FT-IR) was used to investigate the biophysical changes on treatment with fatty acid/EtOH or neat fatty acid, mainly focusing on the infrared region at 2,920, 1,710 and 1,720 cm(-1). Unsaturated fatty acids showed higher enhancement than LA, and the enhancement increased with the number of double bonds. On the other hand, in the presence of iontophoresis, LA/EtOH showed the highest enhancement. Neat LOA did not show any significant difference (p > 0.05) compared to the LOA/EtOH combination. FT-IR studies revealed that fatty acids act by interacting with the skin lipids. All the fatty acids showed synergistic enhancement when combined with iontophoresis. The flux enhancement was highest with LA, which in the presence of iontophoresis showed 20 times enhancement of insulin flux in comparison to passive flux and 9 times enhancement as compared to iontophoresis alone. Flux enhancement of unsaturated fatty acids was in the following decreasing order LOA > OA > LLA.