Influence of electronic and formulation variables on transdermal iontophoresis of tacrine hydrochloride

Beyond Skin Deep: Phospholipid-Based Nanovesicles as Game-Changers in Transdermal Drug Delivery

Transdermal administration techniques have gained popularity due to their advantages over oral and parenteral methods. Noninvasive, self-administered delivery devices improve patient compliance and control drug release. Transdermal delivery devices struggle with the skin's barrier function. Molecules over 500 Dalton (Da) and ionized compounds don't permeate through the skin. Drug encapsulation in phospholipid-based vesicular systems is the most effective skin delivery technique. Vesicular carriers include bi-layered liposomes, ultra-deformable liposomes, ethanolic liposomes, transethosomes, and invasomes. These technologies enhance skin drug permeation by increasing formula solubilization, partitioning into the skin, and fluidizing the lipid barrier. Phospholipid-based delivery systems are safe and efficient, making them a promising pharmaceutical and cosmeceutical drug delivery technique. Still, making delivery systems requires knowledge about the physicochemical properties of the drug and carrier, manufacturing and process variables, skin delivery mechanisms, technological advances, constraints, and regulatory requirements. Consequently, this review covers recent research achievements addressing the mentioned concerns.

Current Advances in Lipid Nanosystems Intended for Topical and Transdermal Drug Delivery Applications

Skin delivery is an exciting and challenging field. It is a promising approach for effective drug delivery due to its ease of administration, ease of handling, high flexibility, controlled release, prolonged therapeutic effect, adaptability, and many other advantages. The main associated challenge, however, is low skin permeability. The skin is a healthy barrier that serves as the body's primary defence mechanism against foreign particles. New advances in skin delivery (both topical and transdermal) depend on overcoming the challenges associated with drug molecule permeation and skin irritation. These limitations can be overcome by employing new approaches such as lipid nanosystems. Due to their advantages (such as easy scaling, low cost, and remarkable stability) these systems have attracted interest from the scientific community. However, for a successful formulation, several factors including particle size, surface charge, components, etc. have to be understood and controlled. This review provided a brief overview of the structure of the skin as well as the different pathways of nanoparticle penetration. In addition, the main factors influencing the penetration of nanoparticles have been highlighted. Applications of lipid nanosystems for dermal and transdermal delivery, as well as regulatory aspects, were critically discussed.

Effect of Pulsed Direct Current on Iontophoretic Delivery of Pramipexole across Human Epidermal Membrane In Vitro

PURPOSE

Pulsed direct current (PDC) iontophoresis, by allowing skin depolarization, was suggested to provide more efficient ion transport, but the extent of its enhancement effect was unclear. PDC could also offer electric-customized drug delivery. This study examined the effect of PDC iontophoresis on transdermal delivery of pramipexole dihydrochloride (PXCl).

METHODS

Iontophoretic delivery of PXCl across human epidermal membrane from pH 7.0 solution was conducted in vitro using continuous direct current (DC) and 6- and 12-cycle PDC iontophoresis (0.5 mA/cm² and total applied duration of 6 h). Different parameters of PDC iontophoresis were studied, including current density (0.1, 0.2 and 0.5 mA/cm²) and on-off current dosing pattern (1 h/3 h, 0.5 h/3.5 h, and 0.2 h/3.8 h).

RESULTS

Both 6- and 12-cycle PDC iontophoresis protocols provided modulation of the permeation profile but delivered smaller amounts of PXCl (396 and 400 μg/cm², respectively) as compared with continuous DC iontophoresis (482 μg/cm²) at 24 h after 0.5 mA/cm² and 180 mA/cm² × min current dose application. Increasing applied current density from 0.1 to 0.5 mA/cm² increased the PDC iontophoretic flux of PXCl linearly from 5.3 to 14.6 μg/cm²·h (R² = 0.887). Varying the current level and duration but at the same applied current dose (36 mA/cm² × min), the total amount of PXCl delivered by PDC iontophoresis at 24 h was independent of the on-off dosing pattern studied (114-128 μg/cm²).

CONCLUSIONS

The results indicate that PDC iontophoresis can benefit transdermal delivery of PXCl in terms of controlling its permeation but does not enhance iontophoretic transport compared to continuous DC iontophoresis under the conditions studied.

Development and cathodic iontophoretic permeation evaluation of liquid crystalline systems provided of retinoic acid microparticles

BACKGROUND

The intracellular form of action of retinoids requires these agents to reach deeper layers of the skin with viable cells to ensure therapeutic efficiency. However, studies on swine skin models show that some retinoids have low skin permeability. Thus, the association of innovative formulations with technological strategies involving physical permeation promoters can be employed to increase the permeability of this active, ensuring a targeting effect of the active.

AIMS

In this study, it was proposed the development and evaluation of the release and permeation profile of liquid crystalline systems with retinoic acid polymeric microparticles under passive or iontophoretic diffusional conditions.

METHODS

For this study, release, permeation, and diffusional characterization assays were employed using the Franz diffusion cell model, associating or not the cathodic iontophoresis.

RESULTS

Retinoic acid was considered stable in front of the electric current of 0.5mA/cm² , because it did not show significant degradation (with maintenance from 96.03% to 98.57%), indicating the viability of such agents to be applied with iontophoresis. Controlled release profile was evidenced for microencapsulated systems. Comparatively, formulations F1, F3, and F5 presented a significantly higher RA release profile when compared to formulations with retinoic acid microencapsulated. A significant increase was observed in the absolute amount of RA retained in the skin with cathodic iontophoresis in all proposed formulations (P < .01). The increase was up to two times in relation to the passive condition.

CONCLUSIONS

The combination of iontophoresis technique with application of retinoic acid and microencapsulated retinoic acid allows the penetration of the active ingredient to deeper layers of the skin.

Current advances in transdermal delivery of drugs for Alzheimer's disease

Alzheimer's disease (AD) is a common, progressive, fatal neurodegenerative disorder, which will play an increasingly important role both socially and financially in the aging populations. Treatments for AD show modest improvements in cognition and global functioning among patients. Furthermore, the oral administration of treating AD has had some drawbacks that decrease the medication adherence and efficacy of the therapy. Transdermal drugs are proposed as an alternative remedy to overcome the disadvantages of current pharmaceutical dosage options for this chronic disorder. They could have different strengths, such as offering a stable diffusion of active substance, avoiding the first pass metabolism, and reducing system adverse reactions. This article reviews the technical principles, novel techniques of transdermal delivery drug, and prospects for future development for the management of cognitive and behavioral dysfunctions in AD patients.

Recent Advances in Lipid-Based Vesicles and Particulate Carriers for Topical and Transdermal Application

In the recent decade, skin delivery (topical and transdermal) has gained an unprecedented popularity, especially due to increased incidences of chronic skin diseases, demand for targeted and patient compliant delivery, and interest in life cycle management strategies among pharmaceutical companies. Literature review of recent publications indicates that among various skin delivery systems, lipid-based delivery systems (vesicular carriers and lipid particulate systems) have been the most successful. Vesicular carriers consist of liposomes, ultradeformable liposomes, and ethosomes, while lipid particulate systems consist of lipospheres, solid lipid nanoparticles, and nanostructured lipid carriers. These systems can increase the skin drug transport by improving drug solubilization in the formulation, drug partitioning into the skin, and fluidizing skin lipids. Considering that lipid-based delivery systems are regarded as safe and efficient, they are proving to be an attractive delivery strategy for the pharmaceutical as well as cosmeceutical drug substances. However, development of these delivery systems requires comprehensive understanding of physicochemical characteristics of drug and delivery carriers, formulation and process variables, mechanism of skin delivery, recent technological advancements, specific limitations, and regulatory considerations. Therefore, this review article encompasses recent research advances addressing the aforementioned issues.

Transdermal iontophoretic delivery of tacrine hydrochloride: Correlation between in vitro permeation and in vivo performance in rats

The aim of present investigation is to evaluate the feasibility of transdermal iontophoretic delivery of tacrine hydrochloride in Sprague Dawley (SD) rats using anodal iontophoretic patches and to correlate plasma tacrine concentration profiles to in vitro tacrine permeation flux. In vitro skin permeation studies were carried out across artificial membrane CELGRAD^® 2400, freshly excised SD rat abdominal skin, freshly excised hairless rat abdominal skin, and frozen pig skin to examine the role of permeation membranes. Furthermore, plasma profiles with an application of 0.1-0.3mA current strength and tacrine concentration loading of 5-20mg/ml were obtained in SD rats. The tacrine plasma profiles were fitted to one-compartmental model using WinNonlin and in vivo transdermal absorption rates were then correlated to in vitro permeation profiles using various approaches. Tacrine permeation across membranes revealed current dependent interspecies differences at lower current strength application which diminished at higher current strength application, whereas, no significant difference in tacrine permeation was observed across fresh and frozen SD rat skin under 0.2mA current application. In vivo studies confirmed current and concentration dependent tacrine plasma profiles with possible tacrine depot formation under the skin in-line with earlier in vitro results. Correlation of in vivo transdermal absorption rates to in vitro permeation profiles revealed higher in vitro permeation fluxes compare to in vivo transdermal absorption rates at varied combination of current strength and concentrations. Present in vivo studies support the earlier published in vitro findings and tacrine plasma profiles show a potential to reach therapeutic effective concentration of tacrine hydrochloride to provide a platform for pre-programmed tacrine delivery.