Controlled iontophoretic delivery of pramipexole: electrotransport kinetics in vitro and in vivo

Iontophoresis for the cutaneous delivery of nanoentraped drugs

INTRODUCTION

The skin is an attractive route for drug delivery. However, the stratum corneum is a critical limiting barrier for drug permeation. Nanoentrapment is a way to enhance cutaneous drug delivery, by diverse mechanisms, with a notable trend of nanoparticles accumulating into the hair follicles when topically applied. Iontophoresis is yet another way of increasing drug transport by applying a mild electrical field that preferentially passes through the hair follicles, for being the pathway of lower resistance. So, iontophoresis application to nanocarriers could further increase actives accumulation into the hair follicles, impacting cutaneous drug delivery.

AREAS COVERED

In this review, the authors aimed to discuss the main factors impacting iontophoretic skin transport when combining nanocarriers with iontophoresis. We further provide an overview of the conditions in which this combination has been studied, the characteristics of nanosystems employed, and hypothesize why the association has succeeded or failed to enhance drug permeation.

EXPERT OPINION

Nanocarriers and iontophoresis association can be promising to enhance cutaneous drug delivery. For better results, the electroosmotic contribution to the iontophoretic transport, mainly of negatively charged nanocarriers, charge density, formulation pH, and skin models should be considered. Moreover, the transfollicular pathway should be considered, especially when designing the nanocarriers.

Passive and iontophoretic transport of pramipexole dihydrochloride across human skin microchannels created by microneedles in vitro

Skin microchannels (MCs) created by microneedles (MNs) provide a promising route for enhancing transdermal drug delivery. This study investigated passive and iontophoretic transport of pramipexole dihydrochloride (PXCl) across skin MCs created by polymer MN patches made of 1:2 polymethyl-vinyl-ether-co-maleic acid (PMVEMA) to polyvinyl alcohol (PVA) ratio. Permeation studies were performed in vitro using excised human skin under the conditions of (i) "poke-and-patch" and "poke-and-release" delivery approaches with varying concentration of PXCl in the formulations, (ii) drug-loaded dissolving MN (DMN) and hydrogel-forming MN (HGMN) type patches and (iii) combination of MNs and iontophoresis. The results showed that DMN patch greatly enhanced transdermal delivery of PXCl for both "poke-and-patch" and "poke-and-release" approaches as compared with the conventional delivery method. PXCl flux mainly resulted from the contribution of MC pathway created in skin and increased with increasing drug amounts in the formulations. Compared to DMN patch, HGMN patch provided more linear sustained drug delivery over 72 h. Electromigration was the main mechanism of PXCl iontophoresis through MCs and flux enhancement was found to be larger for HGMN patch than DMN patch. These results demonstrated the potential application of MN patches individually or combined with iontophoresis as an alternative method for PXCl administration.

Electrically controlled nicotine delivery through Carbon nanotube membranes via electrochemical oxidation and nanofluidically enhanced electroosmotic flow

A promising tool for nicotine addiction treatment is a programmable nicotine delivery device coupled to smart phone-assisted behavioral therapies. Key metrics for such a device are delivery of adjustable nicotine doses tailored to individual needs, compact size and power efficiency. Reported here is a detailed optimization of carbon nanotube (CNT) membrane fabrication based on electrochemical oxidation, to improve its electrically driven performance for nicotine fluxes and switching ON (-1.5 V)-OFF (0 V) flux ratio. ON- state nicotine flux of ~ 6 µmoles/cm²/h at -1.5 V applied bias was achieved allowing ~ 6-folds decrease in the size of device (4 cm²) to attain flux equivalent to high dose nicotine gum (1.1 µmoles/cm²/h). Application of + 1.5 V bias in OFF state reduced diffusional background flux, giving an ON (-1.5 V)/OFF (+ 1.5 V) flux ratio of 68 that enabled device to deliver between the highest nicotine gum (1.1 µmoles/cm²/h) and lowest nicotine patch (0.08 µmoles/cm²/h) doses, as well as taper off nicotine doses for long term addiction treatment. The nicotine transport mechanism was studied as a function of pH and applied bias, using neutral tracer molecule, showing a mechanism of both electroosmosis and electrophoresis in the atomically smooth nanofluidic pores of CNTs. Optimal power consumption/flux efficiency of 111(µW/cm²)/µmoles/cm²/h was achieved allowing watch-battery lifetimes of 7-62 days for conventional treatment dosing regimens. Bluetooth-enabled, remotely controlled CNT membrane system has potential for treatments of nicotine, opioid and alcohol addictions that needs dose adjustment with precise temporal control.

Current profile controlled transdermal delivery of pramipexole from an iontophoretic patch system in vitro and in vivo

The objective was to evaluate the transdermal iontophoretic delivery of pramipexole using constant and complex multi-phasic current profiles from an iontophoretic patch system in vitro and in vivo. Preliminary in vitro experiments were performed to optimize iontophoretic patch design and configuration. "Single" compartment systems containing only pramipexole dihydrochloride, and designed to maximize delivery efficiency, suffered from an insufficiency of chloride ions with anodal electrochemistry passing from an Ag/AgCl couple to an Ag dissolution electrode. Addition of NaCl to provide more chloride ions decreased pramipexole delivery efficiency due to competition between pramipexole and sodium cations. A "two-compartment" iontophoretic patch where the drug reservoir was separated from the anodal compartment, which now included NaCl, was shown to be a good compromise since it ensured Ag/AgCl electrochemistry at the anode and an acceptable delivery efficiency. In vivo studies using this iontophoretic patch demonstrated that the plasma concentration of pramipexole closely followed the variation of the applied continuous and multi-phasic current profiles and underlined the control provided by iontophoresis and its unique ability to rapidly change drug input rates. The applied current density and duration of current application were also shown to modulate pramipexole delivery to the brain and CSF.

Effect of pH on Iontophoretic Transport of Pramipexole Dihydrochloride across Human Epidermal Membrane

PURPOSE

Drugs with higher molecular charges generally show higher flux enhancement when electromigration is the main mechanism in transdermal iontophoresis. This study evaluated the effect of decreasing the formulation pH to increase the positive charges of pramipexole dihydrochloride (PXCl) on its iontophoretic transport across skin.

METHODS

In vitro transdermal iontophoresis of PXCl in buffer solution isotonized with either sodium chloride or mannitol were performed in a pH range of 3.0-7.0. Experiments of iontophoresis under symmetric condition with respect to donor and receiver pH and passive transport of the drugs after pretreatment with iontophoresis were conducted to investigate the transport mechanism involved.

RESULTS

Iontophoretic permeation of PXCl was pH-dependent in drug solution isotonized with mannitol. The iontophoretic flux of PXCl with valence z = +2 at pH 3.0 was half of that of PXCl with z = +1 at pH 7.0. The results suggest that the decrease in PXCl delivery at higher valence at pH 3 was mainly due to pH-dependent selectivity of PX ion permeation across the skin and not electroosmosis.

CONCLUSIONS

Skin permselectivity is a significant factor for iontophoretic transport of PXCl, and reducing formulation pH to increase the positive charges on PX ions did not enhance PXCl delivery.

Effect of continuous and multi-phasic current profiles on the iontophoretic transport of pramipexole, rasagiline and huperzine A: Depicting temporal variation and biodistribution in the skin

Transdermal iontophoresis is an interesting option for the non-invasive controlled delivery of therapeutic agents to treat neurodegenerative diseases. The current profile controls drug delivery kinetics and enables complex drug input profiles to be obtained. The aim of this study was to investigate the temporal variation in transport of pramipexole (PRA), rasagiline (RAS) and huperzine A (HUP) using continuous and multi-phasic current profiles by measuring cumulative permeation, transdermal flux and drug retention in the skin upon modulation of the applied current profile during a single experiment in vitro. Initial experiments with continuous current were conducted to establish a correlation between total delivery of PRA, RAS and HUP (i.e. sum of the cumulative permeation and skin deposition) and the amount of charge transferred. Subsequent experiments with multi-phasic current profiles, confirmed that the relationship between amounts of charge transferred and total delivery was able to predict the total delivery of each drug. Experimental values were within ± 15% of the predicted values. Current density and duration of current application were also shown to have a significant impact on the skin biodistribution of PRA. These results also provide insight into the rate of formation of iontophoretic drug reservoirs in the skin.

Non-invasive targeted iontophoretic delivery of cetuximab to skin

Background: Cetuximab (CTX) is a glycosylated anti-EGFR monoclonal antibody of great interest in the treatment of non-melanoma skin cancers. Its intravenous administration is associated with severe side effects. This is the first report on the noninvasive iontophoretic-targeted topical delivery of CTX to skin.Methods: Iontophoretic transport of CTX (0.5 mA/cm²) was studied as a function of formulation pH (4, 5.5 and 7) and duration of current application (2, 4 and 8 h). CTX cutaneous biodistribution was determined; electrotransport mechanisms and penetration pathways were investigated.Results: Electrophoretic mobility measurements of CTX isoforms and co-iontophoresis of acetaminophen at each pH demonstrated that CTX electrotransport was due to electroosmosis: despite an ~8-fold reduction in charge, CTX skin deposition was greater at pH 7 than pH 4 (8.974 ± 1.952 and 0.482 ± 0.165 μg/mm³) - consistent with the increased electroosmotic flow at pH 7. Iontophoresis of an Alex488-CTX conjugate showed that skin penetration occurred by the intercellular and follicular routes. Therapeutic concentrations of CTX in the viable epidermis, upper dermis and lower dermis were achieved following iontophoresis for 2, 4 and 8 h, respectively.Conclusion: The results demonstrate the topical delivery of a 152 kDa monoclonal antibody into skin in a targeted, controlled and entirely noninvasive manner.

Controlled Iontophoretic Delivery in Vitro and in Vivo of ARN14140-A Multitarget Compound for Alzheimer's Disease

ARN14140 is a galantamine-memantine conjugate that acts upon both cholinergic and glutamatergic pathways for better management of Alzheimer's disease. Poor oral bioavailability and pharmacokinetics meant that earlier preclinical in vivo studies employed intracerebroventricular injection to administer ARN14140 directly to the brain. The aim of the present study was to evaluate the feasibility of using constant current transdermal iontophoresis for the noninvasive systemic delivery of ARN14140 and to quantify the amounts present in the blood and the brain. Preliminary experiments in vitro were performed using porcine skin and validated with human skin. Cumulative ARN14140 permeation across the skin increased linearly with current density and concentration. Delivery efficiency (i.e., fraction of the amount applied that is delivered) reached an exceptional 76.9%. Statistically equivalent delivery was observed after iontophoresis across human and porcine skin. In vivo studies in male Wistar rats showed that iontophoretic transport of ARN14140 could be controlled using the current density (426.7 ± 42 and 1118.3 ± 73 nmol/cm² at 0.15 and 0.5 mA/cm² for 6 h) and demonstrated that transdermal iontophoresis was able to deliver ARN14140 noninvasively to the brain. This is the first report quantifying drug levels in the blood and the brain following transdermal iontophoresis.

Drug Transport across Porcine Intestine Using an Ussing Chamber System: Regional Differences and the Effect of P-Glycoprotein and CYP3A4 Activity on Drug Absorption

Drug absorption across viable porcine intestines was investigated using an Ussing chamber system. The apparent permeability coefficients, P_app,pig, were compared to the permeability coefficients determined in humans in vivo, P_eff,human. Eleven drugs from the different Biopharmaceutical Classification System (BCS) categories absorbed by passive diffusion with published P_eff,human values were used to test the system. The initial experiments measured P_app,pig for each drug after application in a Krebs–Bicarbonate Ringer (KBR) buffer and in biorelevant media FaSSIF V2 and FeSSIF V2, mimicking fasted and fed states. Strong sigmoidal correlations were observed between P_eff,human and P_app,pig. Differences in the segmental P_app,pig of antipyrine, cimetidine and metoprolol confirmed the discrimination between drug uptake in the duodenum, jejunum and ileum (and colon); the results were in good agreement with human data in vivo. The presence of the P-gp inhibitor verapamil significantly increased P_app,pig across the ileum of the P-gp substrates cimetidine and ranitidine (p < 0.05). Clotrimazole, a potent CYP3A4 inhibitor, significantly increased P_app,pig of the CYP3A4 substrates midazolam, verapamil and tamoxifen and significantly decreased the formation of their main metabolites. In conclusion, the results showed that this is a robust technique to predict passive drug permeability under fasted and fed states, to identify regional differences in drug permeability and to demonstrate the activity of P-gp and CYP3A4.

Pramipexole nanocrystals for transdermal permeation: Characterization and its enhancement micro-mechanism

The purpose of the study was to improve transdermal delivery of pramipexole via nanocrystals and investigate the enhancement micro-mechanism. Pramipexole nanocrystals were prepared using wet media milling method and incorporated into carbomer gel. In vitro permeation studies through rabbit ear skin indicated that the cumulative permeation amount of pramipexole from nanocrystals in 24 h was 2.75 times more than that from coarse suspension. Investigations of selective follicular closing technique indicated that approximately 33.88% of the total permeation from nanocrystals was contributed to the follicular pathway, which was confirmed by scanning electron microscopy images. In vitro permeation and in vivo pharmacokinetic studies indicated that pramipexole from nanocrystal gel showed a higher permeation profile than that from coarse suspension gel. Overall, nanocrystals could improve transdermal delivery of pramipexole through transepidermal and transfollicular pathways by the nanosized particles.

Simultaneous controlled iontophoretic delivery of pramipexole and rasagiline in vitro and in vivo: Transdermal polypharmacy to treat Parkinson's disease

Effective treatment of Parkinson's disease (PD) involves administration of therapeutic agents with complementary mechanisms of action in order to replenish, sustain or substitute endogenous dopamine. The objective of this study was to investigate anodal co-iontophoresis of pramipexole (PRAM; dopamine agonist) and rasagiline (RAS; MAO-B inhibitor) in vitro and in vivo. Passive permeation of PRAM and RAS (20 mM each) across porcine skin after 6 h was 15.7 ± 1.9 and 16.0 ± 2.9 µg/cm², respectively. Co-iontophoresis at 0.15, 0.3 and 0.5 mA/cm² resulted in statistically significant increases in delivery of PRAM and RAS; at 0.5 mA/cm², cumulative permeation of PRAM and RAS was 613.5 ± 114.6 and 441.1 ± 169.2 µg/cm², respectively - corresponding to 38- and 27-fold increases over passive diffusion. Electromigration was the dominant mechanism for both molecules (>80%) and there was no effect on convective solvent flow. Statistically equivalent delivery was observed with human skin. The co-iontophoretic system showed high delivery efficiency with 29% and 35% of the applied amounts of PRAM and RAS being delivered. Preliminary pharmacokinetics studies in rats confirmed that the input rate in vivo was such that therapeutic amounts of the two drugs could be co-administered to humans by transdermal iontophoresis using reasonably sized patches and moderate current densities.

Development of a Prolonged-Release Pramipexole Transdermal Patch: In Vitro and In Vivo Evaluation

The current study aimed to develop a prolonged-release pramipexole (PPX) transdermal patch for the treatment of Parkinson's disease. Permeation parameters of PPX were investigated using human cadaver skin. Pramipexole patches were prepared using DURO-TAK^® pressure-sensitive-adhesive (PSA) and evaluated for drug stability, drug loading, in vitro drug release, and in vitro permeation through mouse skin. The results indicated that blends of DURO-TAK^® 87-2852 and DURO-TAK^® 87-2510 were suitable for creating a prolonged-release PPX patch due to their advantages in drug release, drug loading, and stability. The final formulation consisted of 87-2852/87-2510 (70:30), 10% PG, and 15% PPX and showed a cumulative permeation amount of 1497.19 ± 102.90 μg/cm² with a continuous flux over 6.0 μg/(cm²·h) across human cadaver skin for 7 days. In vivo studies in rats indicated that PPX patch produced a significantly longer (p < 0.001) half-life (t _1/2, 75.16 ± 17.37 h) and mean residence time (MRT, 135.89 ± 24.12 h) relative to oral tablets (Sifrol^®) and had a relative bioavailability of 51.64 ± 21.32%. Therefore, this study demonstrated the feasibility of developing a prolonged-release PPX patch, which proposed the potential to serve as an alternate to conventional oral tablets and may therefore improve patient compliance.

Recent trends in the transdermal delivery of therapeutic agents used for the management of neurodegenerative diseases

With the increasing proportion of the global geriatric population, it becomes obvious that neurodegenerative diseases will become more widespread. From an epidemiological standpoint, it is necessary to develop new therapeutic agents for the management of Alzheimer's disease, Parkinson's disease, multiple sclerosis and other neurodegenerative disorders. An important approach in this regard involves the use of the transdermal route. With transdermal drug delivery systems (TDDS), it is possible to modulate the pharmacokinetic profiles of these medications and improve patient compliance. Transdermal drug delivery has also been shown to be useful for drugs with short half-life and low or unpredictable bioavailability. In this review, several transdermal drug delivery enhancement technologies are being discussed in relation to the delivery of medications used for the management of neurodegenerative disorders.

Solid Microneedles for Transdermal Delivery of Amantadine Hydrochloride and Pramipexole Dihydrochloride

The aim of this project was to study the influence of microneedles on transdermal delivery of amantadine hydrochloride and pramipexole dihydrochloride across porcine ear skin in vitro. Microchannel visualization studies were carried out and characterization of the microchannel depth was performed using confocal laser scanning microscopy (CLSM) to demonstrate microchannel formation following microneedle roller application. We also report, for the first time, the use of TA.XT Plus Texture Analyzer to characterize burst force in pig skin for transdermal drug delivery experiments. This is the force required to rupture pig skin. The mean passive flux of amantadine hydrochloride, determined using a developed LC–MS/MS technique, was 22.38 ± 4.73 µg/cm²/h, while the mean flux following the use of a stainless steel microneedle roller was 49.04 ± 19.77 µg/cm²/h. The mean passive flux of pramipexole dihydrochloride was 134.83 ± 13.66 µg/cm²/h, while the flux following the use of a stainless steel microneedle roller was 134.04 ± 0.98 µg/cm²/h. For both drugs, the difference in flux values following the use of solid stainless steel microneedle roller was not statistically significantly (p > 0.05). Statistical analysis was carried out using the Mann–Whitney Rank sum test.

Transdermal iontophoretic drug delivery: advances and challenges

The stratum corneum continues to pose considerable impediment to transdermal drug delivery. One of the effective ways of circumventing this challenge is through the use of iontophoresis. Iontophoresis uses low-level current to drive charged compounds across the skin. This review discusses progress made in the field of iontophoretic transport of small and large molecules. The major obstacles are also touched upon and advances made in the last few decades described. A number of iontophoretic systems approved for clinical use by regulatory authorities is also discussed.