Investigate the control release effect of ion-pair in the development of escitalopram transdermal patch using FT-IR spectroscopy, molecular modeling and thermal analysis

Long-acting transdermal drug delivery formulations: Current developments and innovative pharmaceutical approaches

Transdermal administration remains an active research and development area as an alternative route for long-acting drug delivery. It avoids major drawbacks of conventional oral (gastrointestinal side effects, low drug bioavailability, and need for multiple dosing) or parenteral routes (invasiveness, pain, and psychological stress and bio-hazardous waste generated from needles), thereby increasing patient appeal and compliance. This review focuses on the current state of long-acting transdermal drug delivery, including adhesive patches, microneedles, and molecularly imprinted polymeric systems. Each subsection describes an approach including key considerations in formulation development, design, and process parameters with schematics. An overview of commercially available conventional (adhesive) patches for long-acting drug delivery (longer than 24 h), the reservoir- and matrix-type systems under preclinical evaluation, as well as the advanced transdermal formulations, such as the core-shell, nanoformulations-incorporated and stimuli-responsive microneedles, and 3D-printed and molecularly imprinted polymers that are in development, is also provided. Finally, we elaborated on translational aspects, challenges in patch formulation development, and future directions for the clinical advancement of new long-acting transdermal products.

Mechanistic insights into the effect of drug content on adhesive properties of transdermal patch containing lidocaine

This study aims to shed light on the relationship between drug content and adhesive properties in drug-in-adhesive transdermal patch, and to elucidate molecular mechanisms from the perspective of polymer chain mobility. Lidocaine was selected as model drug. Two acrylate pressure sensitive adhesives (PSAs) with different polymer chain mobility were synthesized. Tack adhesion, shear adhesion and peel adhesion of PSAs with 0, 5%, 10%, 15% and 20% w/w lidocaine contents were tested. Polymer chain mobility was determined by rheology and modulated differential scanning calorimetry experiments. Drug-PSA interaction was analyzed by FT-IR. The effect of drug content on free volume of PSA were determined by positron annihilation lifetime spectroscopy and molecular dynamics simulation. It was found that the polymer chain mobility of PSA was increased with increasing drug content. Due to the variation of polymer chain mobility, tack adhesion increased, and shear adhesion decreased. It was proved that interactions between polymer chains were destroyed by drug-PSA interactions, free volume between polymer chains was expanded, resulting in the increase of polymer chain mobility. We can conclude that the effect of drug content on polymer chain mobility should be considered, when designing a transdermal drug delivery system with controlled and satisfactory adhesion.

A Review of Clinical Studies Assessing the Therapeutic Efficacy of Escitalopram: A Step Towards Development

BACKGROUND

Major depression is a debilitating, sometimes fatal disorder, deteriorating the quality of life and well-being. Escitalopram showed highly selective and dose-dependent inhibitory activity on human serotonin transport. Selective serotonin reuptake inhibitors (SSRIs) are the first-line drugs to manage major depressive disorder (MDD).

OBJECTIVE

The objective of this study is to explore the therapeutic potential of escitalopram, a clinically approved drug to manage MDD and panic disorders.

METHODS

It emphasizes comparative and clinical trial studies with several pharmacological targets reviewed from the data available on PubMed, Science Direct, Clinicaltrails.gov, and from many reputed foundations.

RESULTS

To highlight the clinical efficacy, safety, recent development, and stable formulation of escitalopram with an increased bioavailability profile. Evidence-based on the available clinical and pharmacoeconomic data, escitalopram represents an effective first-line treatment option for MDD patients.

CONCLUSION

The present review highlights the placebo-controlled clinical studies and the recent development that can be helpful for further research perspectives.

Improved Topical Drug Delivery: Role of Permeation Enhancers and Advanced Approaches

The delivery of drugs via transdermal routes is an attractive approach due to ease of administration, bypassing of the first-pass metabolism, and the large skin surface area. However, a major drawback is an inability to surmount the skin's stratum corneum (SC) layer. Therefore, techniques reversibly modifying the stratum corneum have been a classical approach. Surmounting the significant barrier properties of the skin in a well-organised, momentary, and harmless approach is still challenging. Chemical permeation enhancers (CPEs) with higher activity are associated with certain side effects restricting their advancement in transdermal drug delivery. Furthermore, complexity in the interaction of CPEs with the skin has led to difficulty in elucidating the mechanism of action. Nevertheless, CPEs-aided transdermal drug delivery will accomplish its full potential due to advancements in analytical techniques, synthetic chemistry, and combinatorial studies. This review focused on techniques such as drug-vehicle interaction, vesicles and their analogues, and novel CPEs such as lipid synthesis inhibitors (LSIs), cell-penetrating peptides (CPPs), and ionic liquids (ILs). In addition, different types of microneedles, including 3D-printed microneedles, have been focused on in this review.

Metformin-loaded ethosomes with promoted anti-proliferative activity in melanoma cell line B16, and wound healing aptitude: Development, characterization and in vivo evaluation

The present work deals with the development of metformin-loaded ethosomes for localized treatment of melanoma and wound healing. Different ethosomal formulations were prepared using different concentrations of ethanol adopting injection technique. The developed formulations were investigated for entrapment efficiency, ex-vivo skin permeation, vesicle size, morphology and permeation kinetics. The optimized formulation was loaded in 5 % carbomer gel that was evaluated for skin permeation, cytotoxic effect against melanoma mice B16 cell line and for wound healing action. Ethosomes having 30 % v/v ethanol displayed superior entrapment for metformin % (55.3±0.07) ; and a highly efficient permeation via mice skin (85.8±3.7). The related carbomer ethosomal gel exhibited higher skin permeation compared to the untreated metformin gel (P < 0.001). The metformin ethosomes had a substantial antiproliferative activity against melanoma B16 cells compared to corresponding metformin solution as shown by the lower IC50 values (56.45±1.47 and 887.3±23.2, respectively, P<0.05) and tumour cell viability (P<0.05). The ethosomal system had a significant wound healing action in mice (80.5±1.9%) that was superior to that of the marketed product Mebo® ointment (56±1 %), P<0.05. This ethosomal system demonstrated outstanding induction of the mRNA levels of growth factors (IGF-1, FGF-1, PDGF-B and TGF-β) that are essential in the healing process. Those findings were supported by histopathologic examination of wound sections of different treated groups. Thus, the study proved that metformin ethosomes as a promising drug delivery system and a conceivable therapeutic approach for treatment of melanoma and wound healing.

Investigating how amine structure influences drug-amine ion-pair formation and uptake via the polyamine transporter in A549 lung cells

Transiently associating amines with therapeutic agents through the formation of ion-pairs has been established both in vitro and in vivo as an effective means to systemically direct drug delivery to the lung via the polyamine transport system (PTS). However, there remains a need to better understand the structural traits required for effective PTS uptake of drug ion-pairs. This study aimed to use a structurally related series of amine counterions to investigate how they influenced the stability of theophylline ion-pairs and their active uptake in A549 cells. Using ethylamine (mono-amine), ethylenediamine (di-amine), spermidine (tri-amine) and spermine (tetra-amine) as counterions the ion-pair affinity was shown to increase as the number of protonated amine groups in the counterion structure increased. The mono and diamines generated a single hydrogen bond and the weakest ion-pair affinities (pK_FTIR: 1.32 ± 0.04 and 1.43 ± 0.02) whereas the polyamines produced two hydrogen bonds and thus the strongest ion-pair affinities (pK_FTIR: 1.93 ± 0.05 and 1.96 ± 0.04). In A549 cells depleted of endogenous polyamines using α-difluoromethylornithine (DFMO), the spermine-theophylline uptake was significantly increased (p < 0.05) compared to non-amine depleted cells and this evidenced the active PTS sequestering of the ion-pair. The mono-amine and di-amine failed to enhance theophylline uptake in these A549 cells, but the tri-amine and tetra-amine both almost doubled the theophylline uptake into the cells when compared to the uptake of free drug. As the data indicated that polyamines with at least 3 amines were required to form ion-pairs that could enhance A549 cell uptake, it suggested that at least two amines were required to physically stabilise the ion-pair and one to interact with the PTS.

Transdermal Route: A Viable Option for Systemic Delivery of Antidepressants

The high rise in the population suffering from depression depicts the need for improved and highly effective treatment options for this condition. Efforts to develop existing drugs into user-friendly dosage forms with a number of advantages in major depressive states, including but not limited to: sustained drug release, reduced drug dosing frequency, improved tolerance and adherence, suitability for use in diverse populations and different treatment scenarios, as well as less central nervous system side effects are required. One such non-invasive drug delivery route that could provide the aforementioned benefits in the treatment of depression is the transdermal route. A number of conventional and emerging transdermal delivery strategies have been investigated for some potent antidepressants and results depict the potential of this route as a viable means for systemic delivery of therapeutically relevant doses of the tested agents, with Emsam®, the commercially available patch of selegiline, being an evidence for the same. The investigated approaches include the formulation of transdermal patches, use of vesicular drug carriers, pro-drug approach, microemulsification, chemical as well as physical enhancement technologies. This review provides a comprehensive account of the rationale, developments made till date, scope and future prospects of delivering antidepressants via the transdermal1 route of administration.

Development of long-acting rivastigmine drug-in-adhesive patch utilizing ion-pair strategy and characterization of controlled release mechanism

The purpose of present study was to develop a long-acting drug-in-adhesive patch of rivastigmine (RVS) to achieve controlled release under high drug loading. Formulation factors including ion-pair, pressure sensitive adhesive (PSA), drug-loading and permeation enhancers were investigated through in vitro skin permeation experiments. Optimized patch was evaluated by pharmacokinetic study. The mechanism of controlled release was studied by FTIR, Raman, DSC, rheology study and molecular modeling. The optimized patch composed of RVS-SA (equal to 30% RVS), 15% POCC as permeation enhancer and AAOH as PSA matrix. The RVS in optimized patch was basically permeated at a uniform rate, and the ratio of the skin permeation amount (2803.38 ± 153.85 μg/cm²) in 72 hours to that of the control group (1000.89 ± 62.45 μg/cm²) was 2.8. The plasma concentration of RVS was stable for 72 hours in vivo (AUC_optimized = 5721.30 ± 1994.87 h ng/mL, MRT_0-t = 29.55 ± 2.49 h), and C_max was significantly controlled. The results of the study on the controlled release mechanism showed that the addition of counter ion formed hydrogen bonds with RVS and PSA respectively, which reduced the fluidity and molecular mobility of PSA, and enhanced the interaction between RVS and PSA, thus achieving the purpose of long-acting effect. In conclusion, long-acting drug-in-adhesive patch of RVS was developed, and provided a new idea for the long term drug delivery of Alzheimer's disease.

Chiral 4-O-acylterpineol as transdermal permeation enhancers: insights of the enhancement mechanisms of a transdermal enantioselective delivery system for flurbiprofen

In order to devise more effective penetration enhancers, 4-O-acylterpineol derivatives which were expected to be hydrolyzed into nontoxic metabolites by esterase in the living epidermis, were synthesized from 4-terpineol (4-TER) enantiomers and straight chain fatty acids. Their promoting activities on the SR-flurbiprofen and its enantiomers were tested across full-thickness rabbit skin, as well as to correlate under in vitro and in vivo conditions. The permeation studies indicated that both d-4-O-acylterpineol and l-4-O-acylterpineol had significant enhancing effects, interestingly, d-4-O-aclyterpineol had higher enhancing effects than l-4-O-aclyterpineol with the exception of d-4-methyl-1-(1-methylethyl)-3-cyclohexen-1-yl octadec-9-enoate (d-4-T-dC18). The mechanism of 4-O-acylterpineol facilitating the drug penetration across the skin was confirmed by Attenuated total reflection-Fourier transformed infrared spectroscopy (ATR-FTIR) and molecular simulation. The mechanism of penetration enhancers promoting drug release was explored by the in vitro release experiment. Finally, a relative safety skin irritation of enhancers was also investigated by in vivo histological evaluation. The present research suggested that d-4-O-aclyterpineol and l-4-O-aclyterpineol could significantly promote the penetration of SR-flurbiprofen and its enantiomers both in vitro and in vivo, with the superiorities of high flux and low dermal toxicity.

Alternative therapy of rheumatoid arthritis with a novel transdermal patch containing Siegesbeckiae Herba extract

ETHNOPHARMACOLOGICAL RELEVANCE

Siegesbeckiae Herba (SiH) is a traditional anti-rheumatic herbal medicine in China. A SiH derived product, Phynova Joint and Muscle Relief Tablets™, has been granted the UK license in 2015. Although transdermal delivery provides better patient compliance and relative constant plasma drug concentration, the feasibility of transdermal delivery of SiH was not clear.

AIM OF THE STUDY

The aim of the present study was to develop a novel transdermal patch containing SiH extract for alternative therapy of rheumatoid arthritis.

MATERIALS AND METHODS

SiH extract containing 48.5% (w/w) of kirenol was prepared from Siegesbeckia pubescens Makino. Then transdermal patches containing SiH extract were prepared by the solvent evaporation technique. The formulation of the transdermal patch was optimized based on the in vitro skin permeation experiment. Finally, the anti-inflammatory and analgesic activity of the optimal patch were evaluated by chronic inflammation model induced by complete Freund's adjuvant (CFA) and writhing model induced by acetic acid, separately.

RESULTS

Oleic acid (OA) showed the maximum permeation enhancement effect with the enhancement ratio (ER) values of 3.32. Therefore, OA was used as a permeation enhancer in the transdermal patch. The optimal formulation consisted of SiH extract (10% of the matrix, w/w), OA (10% of the matrix, w/w), DURO-TAK® 87-2287 (pressure sensitive adhesive matrix) and Scotchpak™ 9701 (backing layer). The optimal transdermal patch containing SiH extract significantly reduced the degree of paw swelling and number of writhing in inflammation model and writhing model, respectively.

CONCLUSIONS

The developed transdermal patch containing Siegesbeckiae Herba extract showed good anti-inflammatory and analgesic effects, which demonstrated a great potential for alternative therapy of rheumatoid arthritis.

Enhancement strategies for transdermal drug delivery systems: current trends and applications

Transdermal drug delivery systems have become an intriguing research topic in pharmaceutical technology area and one of the most frequently developed pharmaceutical products in global market. The use of these systems can overcome associated drawbacks of other delivery routes, such as oral and parenteral. The authors will review current trends, and future applications of transdermal technologies, with specific focus on providing a comprehensive understanding of transdermal drug delivery systems and enhancement strategies. This article will initially discuss each transdermal enhancement method used in the development of first-generation transdermal products. These methods include drug/vehicle interactions, vesicles and particles, stratum corneum modification, energy-driven methods and stratum corneum bypassing techniques. Through suitable design and implementation of active stratum corneum bypassing methods, notably microneedle technology, transdermal delivery systems have been shown to deliver both low and high molecular weight drugs. Microneedle technology platforms have proven themselves to be more versatile than other transdermal systems with opportunities for intradermal delivery of drugs/biotherapeutics and therapeutic drug monitoring. These have shown that microneedles have been a prospective strategy for improving transdermal delivery systems.

Mechanistic insights of the controlled release capacity of polar functional group in transdermal drug delivery system: the relationship of hydrogen bonding strength and controlled release capacity

Background

Hydrogen bonding interaction was considered to play a critical role in controlling drug release from transdermal patch. However, the quantitative evaluation of hydrogen bonding strength between drug and polar functional group was rarely reported, and the relationship between hydrogen bonding strength and controlled release capacity of pressure sensitive adhesive (PSA) was not well understood. The present study shed light on this relationship.

Methods

Acrylate PSAs with amide group were synthesized by a free radical-initiated solution polymerization. Six drugs, i.e., etodolac, ketoprofen, gemfibrozil, zolmitriptan, propranolol and lidocaine, were selected as model drugs. In vitro drug release and skin permeation experiments and in vivo pharmacokinetic experiment were performed. Partial correlation analysis, fourier-transform infrared spectroscopy and molecular simulation were conducted to provide molecular details of drug-PSA interactions. Mechanical test, rheology study, and modulated differential scanning calorimetry study were performed to scrutinize the free volume and molecular mobility of PSAs.

Results

Release rate of all six drugs from amide PSAs decreased with the increase of amide group concentrations; however, only zolmitriptan and propranolol showed decreased skin permeation rate. It was found that drug release was controlled by amide group through hydrogen bonding, and controlled release extent was positively correlated with hydrogen bonding strength.

Conclusion

From these results, we concluded that drugs with strong hydrogen bond forming ability and high skin permeation were suitable to use amide PSAs to regulate their release rate from patch.

Ethosomal Gel for Improving Transdermal Delivery of Thymosin β-4

Purpose

Thymosin β-4(Tβ-4) is a macromolecular protein drug with potential for drug development in wound repair but is limited by the shortcomings of macromolecular protein, such as large volumes, poor membrane permeability, and unstable physicochemical characteristics. Ethosomes could enhance cell membrane fluidity and reduce epidermal membrane density to make macromolecular drugs through the stratum corneum into the deeper layers of the skin easily. Herein, we developed and characterized a novel transdermal delivery vehicle to load macromolecular protein peptides and use Tβ-4 as a model drug wrapped into ethosomes.

Methods

We used the orthogonal method to optimize the formulation of the ethosome preparation prepared by the ethonal infusion method. Ethosomal gels were characterized by using different analytical methods. Transdermal release rate in vitro have been demonstrated in Franz diffusion cells and the efficacy of drug-loaded nanocarriers in vivo was investigated in a mouse model.

Results

Optimized Tβ-4 ethosomal gels have good physicochemical properties. The drug amounts of the cumulative release in the ethosomal gel within 5 hours were 1.67 times that of the T-β4 gel in vitro release study, and the wound healing time of ethosomal gel group was only half of the T-β4 gel group in vivo pharmacokinetic study. Compared with the free drug group, the ethosome preparation not only promotes the percutaneous absorption process of the macromolecular protein drugs but also shortened wound recovery time.

Conclusion

Hence, we provide a possible good design for ethosomal gel system that can load macromolecular protein peptide drugs to achieve transdermal drug administration, promoting the percutaneous absorption of the drug and improving the effect.

Probing the Role of Ion-Pair Strategy in Controlling Dexmedetomidine Penetrate Through Drug-in-Adhesive Patch: Mechanistic Insights Based on Release and Percutaneous Absorption Process

The purpose of present study was to develop a controlled release drug-in-adhesive patch for transdermal delivery of dexmedetomidine (Dex) using ion-pair technique. Based on the in vitro transdermal experiment, the role of ion-pair on the Dex release behavior and percutaneous absorption process was also investigated. Fourier transform infrared spectroscopy (FTIR), molecular modeling, differential scanning calorimetry (DSC), and rheological test were conducted to probe the effect of ion-pair on the Dex release from patch. Besides, the tape stripping test, attenuated total reflectance Fourier transform infrared (ATR-FTIR), and molecular simulation were carried out to elaborate the action of ion-pair on the Dex percutaneous permeation process. Results showed that the optimized patch prepared with Dex-salicylic acid (SA) showed zero-order skin permeation profile within 24 h; Dex-SA had greater hydrogen bonding formation potential with pressure sensitive adhesive (PSA) than Dex, which resulted in the decrease in the formation ability of free volume of PSA and the increase with the improvement of mechanical strength and chain stiffness of PSA and thus controlled the release rate of Dex from transdermal patch. Besides, the physicochemical properties of Dex such as molecular weight and octanol/water partition coefficient were changed after forming ion-pair with SA, which decreased the permeation ability of Dex. In conclusion, a controlled release drug-adhesive patch for Dex was developed and the mechanism study of ion-pair on the Dex release and percutaneous permeation process was proposed at molecular level.

Mechanistic Insights of the Critical Role of Hydrogen Donor in Controlling Drug Release From Acrylate Adhesive

In the present study, a pyrrolidone adhesive and an amide adhesive were synthesized, and their molecular mechanisms of controlled drug release were described. Using zolmitriptan as model drug, in vitro drug release and skin permeation experiments were performed. Adhesive properties were evaluated using modulated differential scanning calorimetry and rheology study. Free volume of polymer was directly obtained by positron annihilation lifetime spectroscopy. Intermolecular interactions between drugs and adhesives were determined by FTIR spectroscopic analysis and molecular simulation. Release percent (24 h) of zolmitriptan from pyrrolidone adhesive was about 55.8 ± 3.1% (w/w), while from amide adhesive, the release percent (24 h) was about 40.1 ± 1.6% (w/w). The free volume sizes of pyrrolidone adhesive and amide adhesive were about 2309.6 ų and 2854.5 ų, respectively, which were much larger than molecular volume of zolmitriptan (about 285.7 ų). Thus, the polymer networks might not hinder drug diffusion from the view of free volume. Comparing chemical structures of pyrrolidone group and primary amide group, the main difference was that primary amide group of amide adhesive possessed 2 hydrogen donors. It was proved that hydrogen bonding between zolmitriptan and hydrogen donor of primary amide group played a critical role in controlling drug release.

Transdermal enhancement strategy of ketoprofen and teriflunomide: The effect of enhanced drug-drug intermolecular interaction by permeation enhancer on drug release of compound transdermal patch

The aim of the present work was to develop compound transdermal patch containing teriflunomide (TEF) and ketoprofen (KTP) using permeation enhancement strategy; reveal the molecular mechanism by which Azone (AZ) promoted transdermal absorption of compound patch through the enhancement of drug-drug intermolecular interaction. The formulation was optimized using in vitro skin permeation study and confirmed with pharmacodynamics study, anti-inflammatory study and analgesics study. Enhanced drug-drug interaction by AZ was characterized using FT-IR, ¹³C NMR, molecular modeling and thermal analysis. The optimized formulation was composed of TEF (3%), KTP (2%), AZ (10%) and DURO-TAK® 87-4098 as adhesive matrix. The skin permeation amount of TEF-KTP combination was promoted by AZ about 1.9 times (594.2 ± 46.8 μg/cm²) and 1.2 times (502.92 ± 24.0 μg/cm²) compared with TEF-AZ and KTP-AZ individual patch. It was proved that the interaction between TEF and KTP via hydrogen bonding was further enhanced by AZ due to the increased molecular mobility of acrylate polymer (ΔT_g = -17.7 °C), which was proved by FTIR and ¹³C NMR spectra. The enhanced drug-drug intermolecular interaction increased drug dispersed status and decreased the quantity of drug's hydrogen bonding site, thus increasing the drug release amount significantly. In conclusion, a compound transdermal patch containing KTP and TEF was developed successfully and a novel enhancement mechanism was clarified at molecular level, which provided reference for the development of novel compound transdermal patch.