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Results for “IONTOPHORESIS”

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PubMed1985

Modulation of neostriatal activity by iontophoresis of ascorbic acid.

Iontophoresis (20-80 nA) of ascorbic acid (AA) accelerated the firing rate of approximately one-third of the neurons tested in the anteromedial neostriatum of anesthetized rats. When administered to neostriatal neurons that were activated by the simultaneous ejection of glutamic acid (GLU), AA excited more than two-thirds of the cells examined, including many that were not excited by AA alone. At ejection currents above 80 nA, AA further increased the activity of some GLU-activated neurons, but suppressed the firing rate of others. Electrochemical quantification of AA ejection during iontophoresis indicated that the concentration of AA at the tip of the recording electrode was within reasonable physiological limits. It is concluded that endogenous AA may modulate neuronal activity in the neostriatum.

Animals↗

PubMed1987

A sputtered gold microelectrode in combination with a multibarrelled micropipette: a low impedance extracellular recording electrode with the facility of iontophoresis.

The manufacture of a metal film electrode on a multibarrelled micropipette is described. Gold film is sputtered onto the external surface of a multibarrelled micropipette and subsequently insulated. Gold film exposed at the tip operates as an extracellular recording microelectrode and the micropipettes may be used for iontophoresis of drugs or marker dyes. This method may be used to produce electrodes with increased numbers of iontophoresis channels at the tip without altering the low impedance and good recording characteristics of the metal film (recording) electrode.

Animals↗

PubMed1986

Iontophoresis of vincristine versus saline in post-herpetic neuralgia. A controlled trial.

Twenty patients with post-herpetic neuralgia (median duration 28.5 months) were randomly allocated to receive transdermal iontophoresis of either vincristine or saline. Although significant improvement in pain by word score and visual analogue scale (P = 0.05) was reported by 6 out of 10 of the vincristine group, none of the patients considered themselves 'cured.' There was no significant change in the saline group. No adverse haematological or neurological side effects were seen, but skin irritation and painless electrical burns were common in both groups. The dramatic relief of pain in patients with post-herpetic neuralgia of 3 months or less reported elsewhere was not seen in our group who had pain of a longer duration. This present trial does not confirm the value of vincristine iontophoresis in the treatment of post-herpetic neuralgia of over 6 months duration.

Aged↗

PubMed2005

Transdermal iontophoresis: combination strategies to improve transdermal iontophoretic drug delivery.

For several decades, there has been interest in using the skin as a port of entry into the body for the systemic delivery of therapeutic agents. However, the upper layer of the skin, the stratum corneum, poses a barrier to the entry of many therapeutic entities. Given a compound, passive delivery rate is often dependent on two major physicochemical properties: the partition coefficient and solubility. The use of chemical enhancers and modifications of the thermodynamic activity of the applied drug are two frequently employed strategies to improve transdermal permeation. Chemical enhancers are known to enhance drug permeation by several mechanisms which include disrupting the organized intercellular lipid structure of the stratum corneum , 'fluidizing' the stratum corneum lipids , altering cellular proteins, and in some cases, extracting intercellular lipids . However, the resulting increase in drug permeation using these techniques is rather modest especially for hydrophilic drugs. A number of other physical approaches such as iontophoresis, sonophoresis, ultrasound and the use of microneedles are now being studied to improve permeation of hydrophilic as well as lipophilic drugs. This article presents an overview of the use of iontophoresis alone and in conjunction with other approaches such as chemical enhancement, electroporation, sonophoresis, and use of microneedles and ion-exchange materials.

Animals↗

PubMed2006

Structure-permeation relationships for the non-invasive transdermal delivery of cationic peptides by iontophoresis.

Transdermal iontophoresis enables the controlled, non-invasive administration of peptide therapeutics. The aims of this study were (i) to evaluate the effect of amino acid sequence and the spatial distribution of peptide physicochemical properties on electrotransport, and (ii) to develop a quantitative model to predict peptide transport rates. Experimental results showed that the distribution of molecular properties over the peptide surface significantly affected iontophoretic delivery: different arrangements of the same residues resulted in different transport behavior. Computational studies generated three-dimensional quantitative structure-permeation relationships (3D-QSPR) based on 3D descriptors. The model predicted that iontophoresis was favored by peptide hydrophilicity but hindered by voluminous, localized hydrophobicity. Molecular characteristics that favor electrotransport are the converse of those required for passive diffusion across biological membranes. The data represent the first analysis of peptide electrotransport in terms of the spatial distribution of molecular properties and provide insight into the ab initio prediction of transdermal iontophoretic peptide delivery.

Administration, Cutaneous↗

PubMed2004

Iontophoresis of lecithin vesicles of cyclosporin A.

Site-specific immunosuppression with topical cyclosporin A (CsA) has broad clinical implications in the treatment of skin disorders like psoriasis, pyoderma gangrenosum, lichen planus, cutaneous graft-versus-host disease and contact hypersensitivity and the temporary treatment of skin allografts on burn wounds. However, like any other peptide drug, its skin delivery is hindered by the barrier property of stratum corneum and the physicochemical properties of CsA. We have attempted to deliver CsA across human cadaver epidermis in vitro using colloidal systems like microemulsion and lecithin vesicles and iontophoresis. Although, passive diffusion did not result in permeation of quantifiable amounts of CsA, anodal iontophoresis of the negatively charged colloidal systems facilitated the permeation. Electroosmosis and compromised epidermis might have contributed to the higher skin flux. Lecithin vesicles were better than microemulsion for the iontophoretic delivery of CsA and appear to have potential in site-specific immunosuppression.

Cyclosporine↗

PubMed2004

Transdermal iontophoresis of rotigotine: influence of concentration, temperature and current density in human skin in vitro.

Iontophoretic transport of rotigotine across human stratum corneum (HSC) was studied in vitro in side by side diffusion cells according to the following protocol: 6 h of passive diffusion, 9 h of iontophoresis followed by 5 h of passive diffusion. A current density of 0.5 mA cm(-2) was applied. The parameters studied were the influence of the rotigotine concentration in donor phase and the influence of the molecular weight of the co-ions. To this end, Na(+) was replaced by tetra ethyl ammonium (TEA(+)) or tetra butyl ammonium (TBA(+)) (both at pH 5 and 6). In addition, the influence of the acceptor phase temperature (32 degrees C versus room temperature), the replacement of HSC by dermatomed human skin (DHS), and the relation between drug transport and current density were examined. The estimated steady-state flux (Flux(ss)) gradually increased with the drug concentration in the donor phase in a linear manner. The flux was also linearly correlated with the applied current density providing a convenient approach to individual dose titration. The use of TEA(+) as co-ion increased the rotigotine iontophoretic flux significantly, while TBA(+) did not. Replacing HSC by DHS reduced the iontophoretic rotigotine transport, while an increase in temperature to 32 degrees C increased the rotigotine flux. The maximum Flux(ss) achieved was around 80 nmol cm(-2) h(-1) indicating that by means of iontophoresis, a therapeutic level of rotigotine might be achieved with a reasonable patch size.

Administration, Cutaneous↗

PubMed2005

Iontophoresis: a non-invasive ocular drug delivery.

Iontophoresis as a non-invasive technique for ocular drug delivery has been investigated for many years. This paper provides an overview of the approaches currently used in the development of the ocular iontophoretic device, the essential features of this procedure and the reported toxicity. This review focuses on the experimental results after transcorneal and transscleral iontophoresis of different drugs, emphasizing the current density applied and the treatment duration used by the investigators.

Administration, Topical↗

PubMed1998

Lidocaine iontophoresis for topical anesthesia before intravenous line placement in children.

In a double-blind randomized trial including 42 children aged 7 to 18 years, less pain occurred with intravenous placement after iontophoresis of 2% lidocaine with epinephrine, as reported by patients (p = 0.005), parents (p = 0.001), intravenous personnel (p = 0.009), and investigators (p = 0.0002) compared with placebo therapy. Lidocaine iontophoresis provides rapid and effective topical anesthesia for intravenous access in children.

Adolescent↗

PubMed1993

Iontophoresis and chloride-containing compounds: parameters required for killing.

Fungi, and gram-positive and gram-negative organisms were susceptible to iontophoretic killing in simple media. Iontophoresis did not depend on electrode type but did require chloride-containing compounds in the medium. All organisms could be killed efficiently if chloride-containing compounds (for example sodium chloride and calcium chloride) were present in physiological concentrations. Effectiveness of iontophoretic killing could be reduced by nonphysiologically elevated concentrations of other substances (for example creatinine and albumin). The data suggest that iontophoresis should function well in urine, since chloride-containing compounds are present in adequate concentrations even if some naturally occurring compounds, such as creatinine or albumin, are elevated.

Calcium Chloride↗

PubMed2003

Local anesthesia reduces the maximal skin vasodilation during iontophoresis of sodium nitroprusside and heating.

AIM: To evaluate the effect of local anesthesia on the skin vasodilation induced by the iontophoresis of sodium nitroprusside and heating. METHODS: Skin vascular reactivity, in response to iontophoresis of sodium nitroprusside (SNP), was evaluated at the forearm and foot in 13 neuropathic diabetic (DN) and 11 nonneuropathic diabetic (D) patients and 9 healthy, nondiabetic subjects who served as controls (C). The direct (DI) and nerve axon reflex-related (N-V) vasodilation were measured by using two single-point laser Doppler probes. The vasodilation in response to local warming was also assessed. A topical anesthetic was applied on the contralateral forearm and foot and all the measurements were repeated. RESULTS: Dermal anesthesia resulted in a reduction of the direct vasodilation to SNP at the forearm [C: 58.1 +/- 16, D: 60.6 +/- 11%, and DN: 48.3 +/- 37% (postanesthesia percentage of reduction; mean +/- SEM), P<0.01] and at the foot in all three groups (D: 38.5 +/- 12%, P<0.01; C: 27.2 +/- 14% and DN: 11.3 +/- 17.5%, P=NS). The N-V related vasodilation was very low before and did not change after local anesthesia. The postanesthesia hyperemic response to warming was significantly reduced at low temperatures but did not change at 44 degrees C. CONCLUSION: The sodium nitroprusside-related vasodilation is reduced after local anesthesia in a similar way in healthy subjects and diabetic patients with and without neuropathy. The response to heating is also reduced at low temperatures. This indicates a stabilizing effect of local anesthesia on the smooth muscle cell.

Administration, Topical↗

PubMed1999

Iontophoresis as a new method of delivering local anesthesia to the urethra: a pilot study.

OBJECTIVES: To test the feasibility of using the iontophoretic catheter as a means of delivering local anesthetic (lidocaine hydrochloride) to the urethra for periurethral injection of collagen. METHODS: Eight women with urodynamically proven genuine stress incontinence underwent periurethral collagen injections. Local anesthesia was provided by 4% lidocaine with 1 in 100,000 epinephrine administered over 10 minutes using an iontophoretic catheter. Pain was assessed by Likert and visual analogue scales. Cystoscopic appearance of the urethra was noted. RESULTS: The periurethral bulking procedure was completed without further anesthetic in 7 women, 1 of whom had no pain. There was no evidence of urethral damage from the iontophoresis. CONCLUSIONS: Iontophoresis shows promise as a method of providing analgesia to the urethra. However, the degree of analgesia is variable, and further research is needed on catheter design to ensure transport of anesthetic agent into the periurethral tissues.

Aged↗

PubMed2003

Alternating-pulse iontophoresis for targeted cutaneous anesthesia.

In studies of sensory contributions to motor control, it may be advantageous to temporarily reduce the sensitivity of specific sensory systems. This article details a method for non-invasively inducing cutaneous anesthesia, leaving proprioceptive and motor functions intact. This method, called alternating-pulse iontophoresis, differs from conventional direct-current (DC) iontophoretic drug delivery in that adjacent drug delivery electrodes are stimulated out-of-phase. The total current delivered at any instant is then less than that produced during a comparable DC application, while the uniformity of drug delivery is expected to improve. Effective delivery of local anesthetics to the cutaneous foot soles by alternating-pulse iontophoresis was demonstrated using cutaneous pressure sensory threshold levels (STL's) assessed with Semmes-Weinstein monofilaments (arbitrary units of perceived force, or a.u.). Thirteen of 16 healthy subjects achieved a level of anesthesia greater than or equal to that normally associated with clinical peripheral sensory neuropathy. Average STL's measured prior to the anesthesia procedure were 4.00 a.u. ( approximately 10 mN). Immediately following the procedure, STL's were elevated to an average of 5.40 a.u. ( approximately 246 mN) and averaged 4.97 a.u. ( approximately 92 mN) after 50 min of standing. A number of research and clinical applications for this technique are suggested.

Administration, Cutaneous↗

PubMed1997

Transdermal therapy and diagnosis by iontophoresis.

Iontophoresis, the use of an electric current to drive charged molecules across the skin, has the potential to expand the feasible range of drugs for transdermal administration significantly. This method of delivery is being examined carefully with respect to higher-molecular-weight therapeutics (in particular, peptides and small proteins), which cannot be absorbed following oral administration and for which, at this time, an invasive injection remains the only option. In addition, the procedure of so-called 'reverse' iontophoresis would appear to represent a truly noninvasive approach for diagnostic monitoring of blood chemistry.

Administration, Cutaneous↗

PubMed2001

A mechanism of the high frequency AC iontophoresis.

The efficiency and the voltage dependence of the AC iontophoresis were studied in vitro. Two cylindrical glass cells separated by a cellophane film were used, where the donor cell was filled with the solution of target electrolytes and the receptor cell with distilled water. The sinusoidal AC voltage with a frequency of 1 kHz was applied between the two platinum plates located at the opposite ends of two cells. The time variation of the ion concentration was evaluated by measuring the impedance of the solution in the receptor cell. The transportation velocity of the ions increased with the amplitude of the voltage applied between two platinum plate electrodes apart 20 mm up to approximately 15 V, and leveled off above approximately 15 V. A theoretical model is proposed on the AC iontophoresis, where each ion moves together with the surrounding water molecules when it is hydrated. The effective Stokes radius of an ion is assumed to be half of the whole size of the ion with hydrating water molecules. When the external alternating electric field strongly vibrates the ion, the ion-dipole interactions between the ion and water molecules are broken, resulting in the reduced effective Stokes radius, which leads to the increase of the diffusion efficiency.

Algorithms↗

PubMed2003

Investigation of properties of human epidermal membrane under constant conductance alternating current iontophoresis.

Previous studies in our laboratory have shown that enhanced, constant permeant fluxes across human skin can be achieved by applying an alternating current (AC) to maintain skin electrical conductance at a constant level. Relative to conventional direct current (DC) iontophoresis, for which current is maintained at a constant level, this newly developed constant conductance alternating current (CCAC) method achieves constant fluxes with less inter- and intra-sample variability. The present study focused upon further investigating the permeability properties of human skin during CCAC iontophoresis at a variety of target resistance/conductance values. A three-stage experimental protocol was used with flux measurements determined on 3 consecutive days. Stage I was an AC only protocol (symmetrical AC square-wave signal), stage II was an AC plus DC protocol (AC square-wave with DC offset voltage), and stage III was a repeat of stage I. During this three-stage protocol, the skin electrical resistance was maintained at a constant target value by manually adjusting the applied AC voltage. Radiolabeled mannitol and urea were model permeants in all experiments. Their fluxes were determined and used to characterize the permeability properties of human skin. The results from the present study established that: (i) the CCAC protocol made it possible to reduce HEM electrical resistance to different target levels as low as 0.8 kOmega cm(2) and maintain the specific resistance level throughout the flux experiment, (ii) permeant fluxes are proportional to skin electrical conductance, (iii) under the studied CCAC passive conditions, membrane pore size tends to increase as skin resistance decreases, and (iv) as the membrane breaks down, its pore sizes become larger.

Administration, Cutaneous↗

PubMed1998

Enhanced transdermal delivery of AZT (Zidovudine) using iontophoresis and penetration enhancer.

The effect of current, its magnitude and penetration enhancers (propylene glycol/oleic acid) on the transdermal flux of AZT (Zidovudine) across hairless mouse skin was studied and the results were compared. The in vitro iontophoretic flux from AZT solution increased to about 5-40 fold that obtained by passive diffusion, depending on the magnitude of current density. When the donor side was karaya gum matrix, instead of solution, the flux enhancement effect by iontophoresis was much smaller. Incorporation of penetration enhancers into the matrix increased the passive flux 2-50 fold, depending on the amount of penetration enhancers in the matrix. These enhancers worked synergistically with iontophoresis in the transdermal transport: a much larger flux than that expected from a simple additive effect was observed. Electrical resistance data from our previous work is utilized to further discuss this synergistic effect.

Administration, Cutaneous↗

PubMed1998

Experimental verification of the mechanistic model for transdermal transport including iontophoresis.

An experimental verification of the previously introduced model for transdermal transport (Kontturi and Murtomäki, J. Control. Release, 41 (1996) 177) is presented. The model comprises two penetration routes: an aqueous and a lipoidal pathway. Lipophilicity of the drug determines which route the drug uses. Constant potential iontophoresis can be used to evaluate the relative proportions of the two competing pathways. beta-blockers sotalol, timolol and propranolol, whose water-octanol partition coefficients span three orders of magnitude, are used as model compounds. Experiments reinforce the predictions of the model in that iontophoresis enhances the flux of the most hydrophilic drug, sotalol, the most whereas the flux of the least hydrophilic drug, propranolol, is enhanced the least. The effect of electroosmosis has now been included in the model.

Administration, Cutaneous↗