Combination of ion-pair strategy and chemical enhancers for design of dexmedetomidine long-acting patches: Dual action mechanism induced longer controlled release and better delivery efficiency

Transdermal patch based on pressure-sensitive adhesive: the importance of adhesion for efficient drug delivery

INTRODUCTION

Transdermal patches offer a unique advantage by providing extended therapeutic benefits while maintaining stable plasma drug concentration. The efficacy and safety of patches depend significantly on their ability to adhere to the skin, a feature influenced by various external and internal factors.

AREAS COVERED

The review primarily focuses on the fundamental aspects of adhesion in transdermal patches, including basic information about the skin, the underlying principles of adhesion, drug delivery, and adhesion characteristics of pressure sensitive adhesives (PSAs), adhesion issues, impact factors, strategies to improve patch adhesion, and relevant molecular mechanisms.

EXPERT OPINION

The development of transdermal patches with sufficient adhesion for consistent and extended drug delivery remains a challenging task. Challenges in adhesion stem from the complex interplay among PSAs, permeation enhancers, active pharmaceutical ingredients (APIs), and other excipients in current patch compositions, further complicated by variations arising from dermatological factors. These intricacies significantly impede the consistent effectiveness of patches. Progress in the exploration of new PSA polymers, in conjunction with innovative patch compositions, is crucial for establishing an optimal equilibrium between drug utilization rate, drug-loading, drug release, and adhesion, thus effectively addressing the challenges related to adhesion.

Application of high-polarity hydroxyl polyacrylate pressure sensitive adhesive in rizatriptan transdermal drug delivery patch

This study aimed to design a rizatriptan (RIZ) transdermal patch by combining of high-polarity hydroxyl pressure sensitive adhesive (PSA) AAOH-45 with an ion-pair strategy and investigate the molecular mechanism of high content hydroxyl PSA to enhance drug-PSA miscibility. RIZ free base, ion-pair complexes and PSAs containing hydroxyl group were prepared and characterized. Formulation factors including counter-ions, PSAs, drug-loading and others were optimized through single-factor studies and evaluated through pharmacokinetic studies and skin irritation tests. The properties of high polarity PSA and molecular mechanism of drug-PSA miscibility were investigated through molecular simulation, FTIR spectra, 13C NMR spectra, DSC, and rheology study. The optimized formulation contained 20 % (w/w) RIZ-OA (Rizatriptan-Oleic acid), 80 % AAOH-45 (w/w) as the matrix, and had a thickness of 90 μm. Compared with the oral group (MRT0-t = 5.96 ± 0.97 h) and the control patch group (MRT0-t = 11.30 ± 1.78 h), the pharmacokinetic behavior of the optimization group demonstrated sustained drug delivery behavior (MRT0-t = 20.21 ± 0.61 h) with no irritation phenomenon. The miscibility of RIZ with PSAs was positively correlated with the mass percentage of 2-HEA. Higher polar similarity, lower flowability, and stronger intermolecular interaction were responsible for the higher compatibility of high hydroxyl PSA with the drug. This study provided a reference for increasing the drug-loading in PSA and developing RIZ patch.

Combining ion-pair strategy and percutaneous permeation enhancers to develop sustained-release paliperidone patch

In this study, a sustained-release paliperidone (PAL) patch was developed using a combination of ion-pair strategy and percutaneous permeation enhancers (PPEs). The ion-pair strategy was used to improve drug-adhesive miscibility and control drug release. PPEs were used to break SC barrier function to facilitate drug skin permeation. The in vitro skin permeation experiments using single-factor experiments and Box-Behnken design gave the optimized formulation, a 55 μm adhesive thickness patch with 7 % (w/w) PAL-LA (Lauric acid), 9.7 % (w/w) Plurol® Oleique CC 497 (POCC). Moreover, the pharmacokinetic study confirmed its potential in sustained-release transdermal patch with longer MRT0-t (18.35 ± 3.11 h) and higher BA (63.14 %) than the gavage group (Cmax = 6.64 ± 2.61 μg/mL, MRT0-t = 2.88 ± 1.06 h, BA = 45.70 %) without significant increasing Cmax. The mechanism study revealed that forming ion-pairs effectively modulated drug's physicochemical properties and doubly ionic H-bond strength to improve drug miscibility in patches. To summarize, a sustained-release patch of PAL was successfully developed, which provided a strategy for sustained-release patches with good drug-polymer miscibility, drug controlled-release, and feasible drug utilization features.

A finasteride patch for the treatment of androgenetic alopecia: A study of promoting permeability strategy using synthetic novel O-acylmenthols combined with ion-pair

Currently, finasteride (FIN) is approved to treat androgenetic alopecia only orally, and the application of FIN in transdermal drug delivery system (TDDS) has introduced a new approach for treating the disease. This study was aimed to develop a FIN transdermal patch for the treatment of androgenetic alopecia（AGA） by combing ion-pair and O-acylmenthols (AM) as chemical permeation enhancers (CPEs). The formulation of patch was optimized though single-factor investigation and Box-Behnken design. The pharmacokinetics and androgenetic alopecia pharmacodynamics of the patch were evaluated. Additionally, the permeability enhancement mechanisms of ion-pair and AMs were explored at both the patch and skin levels. The effects of ion-pair and AMs on the patch were characterized by rheology study, FTIR, and molecular docking, and the effects on the skin were assessed through ATR-FTIR, Raman study, DSC, CLSM and molecular dynamics. The finalized formulation of FIN patches was consisted of 5 % (w/w) synthetic FIN-CA (Citric Acid), 6 % MT-C6 as CPEs, 25-AAOH as a pressure-sensitive adhesive (PSA), with a patch thickness of 80 ± 5 μm. The final Q24 h is 78.22 ± 5.18 μg/cm2. Based on the high FIN permeability, the pharmacokinetic analysis revealed that the FIN patch group exhibited a slower absorption rate (tmax = 7.3 ± 2.7 h), lower peak plasma concentration and slower metabolic rate (t1/2 = 6.2 ± 0.8 h, MRT0-t = 26.0 ± 7.8 h) compared to the oral group. Moreover, the FIN patch also demonstrated the same effect as the oral group in promoting hair growth in AGA mice. The results indicated that both FIN-CA and AMs could enhance the fluidity of the PSA and weaken the interaction between FIN-CA and PSA, thereby promoting the release of the FIN from the patch. The interaction sites on the skin for ion-pair and the four AMs were found in the stratum corneum (SC) of the skin, disrupting the tight arrangement of stratum corneum lipids. This study serves as a reference for the multi-pathway administration of FIN and the combination of ion-pair with AMs to enhance drug permeation.

Innovative Long-Acting Bisoprolol Patch: Synergistic Ion-Pair Skin Adsorption for Drug Delivery Control Coupled with Dynamic Modulation of Penetration Enhancers

This study aims to develop a sustained release patch for bisoprolol (BSP) to address the issue of blood pressure fluctuations caused by traditional dosing methods, ensuring continuous drug release and efficient utilization. Long-chain saturated fatty acids (C6-C12) were chosen as counterions to precisely control BSP's permeation rate in the patch formulation, and the ion-pairing strategy's mechanism in drug delivery was thoroughly investigated. Molecular docking results revealed significant differences in the adsorption capacities of different ion pairs in the stratum corneum (SC) and epidermis, directly influencing their residence times and thereby regulating BSP's passive diffusion rate. Particularly, the BSP-C10 ion pair successfully reduced BSP's permeation rate to one-third of its baseline. To enhance drug delivery efficiency and reduce costs, chemical permeation enhancers (CPEs) are typically added to sustained release patches. In contrast to traditional static analyses based on cumulative permeation, this study utilized ATR-FTIR dynamic detection of isopropyl myristate (IPM) as a preferred enhancer, studying its disruptive effects on the skin barrier during drug delivery. The study observed that during drug delivery, the interaction between IPM and skin lipids follows a U-shaped trend: initially increasing, then decreasing, with the peak occurring at 10 h. Similarly, the drug delivery rate displays a comparable pattern. The addition of IPM as CPE increased the patch utilization rate from 39.8 ± 4.31 to 79.8 ± 7.27%. This strategy aims to rapidly reduce blood pressure in the initial phase with subsequent weakening of IPM disruption, allowing the ion-pairing strategy to dominate drug delivery control and maintain stable long-term therapeutic effects. Pharmacokinetic studies demonstrated that the newly developed BSP sustained release patch maintains stable blood drug concentrations, reduces burst release effects, increases bioavailability to 84.679%, doubles MRT0-t, halves Cmax, and significantly reduces the occurrence of blood pressure fluctuations.

Deep eutectic solvent combined with permeation enhancer strategy to convert tandospirone from oral to transdermal formulations improving drug bioavailability

Tandospirone(Tan) is a commonly used drug for anxiety treatment. However, it has a significant first-pass effect and needs to be taken three times a day. To increase the bioavailability of the drug and reduce the number of administrations, this work amid to prepare a Tan patch that can be administered once a day by using the strategy of therapeutic deep eutectic solvent(THEDES) in cooperation with chemical permeation enhancer(CPE). In this study, four organic acids and five permeation enhancers were selected, and the optimized formulation was obtained by single-factor investigation and Box-Behnken design. The optimized formulation could significantly enhance drug loading by 2.5-fold and skin permeation up to 586.6 ± 17 μg/cm2 in rats. Based on pharmacokinetic results, compared to oral administration, the drug exhibited a substantially elevated bioavailability, registering a 17-fold increase(from 3.01 % to 52.17 %), alongside a 10-fold rise in the mean residence time(MRT). Meanwhile, the patch was not irritating. The results of the mechanistic study showed that levulinic acid(LeA) acted as a bridge to increase the interaction between the Tan and the matrix and inhibited the crystallization of the drug in the patch, and THEDES together with CPE improved the matrix fluidity and skin permeability. This study provides a reference for the joint application of THEDES and CPEs in patch development.

Low drug load, high retention mometasone furoate cream with polyglyceryl - 3 oleate as a chemical enhancer: Formulation development, in vivo and in vitro evaluation and molecular mechanisms

The study aimed to create a low loading, high retention, easier to apply O/W mometasone furoate (MF) cream using a chemical enhancer (CE) approach to provide more options for patients with atopic dermatitis (AD) and to investigate molecular mechanisms of its increased release and retention. A Box-Behnken design determined the optimal formulation based on stability and in vitro skin retention. Evaluations included appearance, rheological properties, irritation, in vivo tissue distribution and pharmacodynamics. Molecular mechanisms of enhanced release were studied using high-speed centrifugation, molecular dynamics and rheology. The interaction between the CE, MF and skin was studied by tape stripping, CLSM, ATR-FTIR and SAXS. The formulation was optimized to contain 0.05% MF and used 10% polyglyceryl-3 oleate (POCC) as the CE. There was no significant difference from Elocon® cream in in vivo retention and pharmacodynamics but increased in vivo retention by 3.14-fold and in vitro release by 1.77-fold compared to the basic formulation. POCC reduced oil phase cohesive energy density, enhancing drug mobility and release. It disrupted skin lipid phases, aiding drug entry and formed hydrogen bonds, prolonging retention. This study highlights POCC as a CE in the cream, offering insights for semi-solid formulation development.

Ionic Liquid Transdermal Patches of Two Active Ingredients Based on Semi-Ionic Hydrogen Bonding for Rheumatoid Arthritis Treatment

Rheumatoid arthritis (RA) is a chronic autoimmune disease that leads to deformities and disabilities in patients. Conventional treatment focuses on delaying progression; therefore, new treatments are necessary. The present study reported a novel ionic liquid transdermal platform for efficient RA treatment, and the underlying mechanism was elucidated using FTIR, 1H-NMR, Raman, XPS, and molecular simulations. The results showed that the reversibility of the semi-ionic hydrogen bonding facilitated high drug loading and enhanced drug permeability. Actarit's drug loading had an approximately 11.34-times increase. The in vitro permeability of actarit and ketoprofen was improved by 5.46 and 2.39 times, respectively. And they had the same significant effect in vivo. Furthermore, through the integration of network pharmacology, Western blotting (WB), and radiology analyses, the significant osteoprotective effects of SIHDD-PSA (semi-ionic H-bond double-drug pressure-sensitive adhesive transdermal patch) were revealed through the modulation of the JAK-STAT pathway. The SIHDD-PSA significantly reduced paw swelling and inflammation in the rat model, and stimulatory properties evaluation confirmed the safety of SIHDD-PSA. In conclusion, these findings provide a novel approach for the effective treatment of RA, and the semi-ionic hydrogen bonding strategy contributes a new theoretical basis for developing TDDS.

Effect of ion pair strategy on transdermal delivery of guanfacine: Which factor dominates drug permeation?

Ion pair is an effective chemical approach to promoting drug transdermal permeation, and the traditional interpretation for its enhanced permeation effect is mainly attributed to counterions altering the physicochemical properties of the drug (lipophilicity, melting point, etc.). In this work, guanfacine (GFC), a non-stimulant for anti-attention deficit and hyperactivity disorder (ADHD), was used as a model drug, and several organic or inorganic acids were designed thereby successfully constructing ion pairs. The transdermal permeation ability of ion pairs through isolated porcine skin was observed and ranked as follows: guanfacine caprylate (GFC-CA) > GFC > guanfacine laurate (GFC-LA) > guanfacine fumarate (GFC-FA) > guanfacine hydrochloride (GFC-HA) > guanfacine palmitate (GFC-PA). The effect of key physicochemical properties (octanol-water partition coefficient, molecular volume, melting point) on the transdermal permeation rate of the model drug was analyzed in detail. In addition, GFC-CA was observed to alter the lipid structure of the skin, suggesting the traditional explanation of the action of ion pair may be inadequate and underrated, and ion pair may also enhance permeation by disrupting skin structure. The intriguing phenomenon is expected to provide a novel approach to achieving precise transdermal drug delivery.

Active pharmaceutical ingredient-ionic liquids assisted follicular co-delivery of ferulic acid and finasteride for enhancing targeted anti-alopecia

Androgenetic alopecia (AGA) is the primary hair loss with impairing patients' quality of life. Finasteride (FIN) is an SRD5A2 inhibitor for AGA treatment, but oral FIN causes systemic adverse effects. Topical FIN delivery is anticipated to overcome this problem. Ferulic acid (FA) is a natural phenolic acid with vascular remodeling and anti-inflammatory effects. Herein, an active pharmaceutical ingredient ionic liquid (API IL) based on choline and FA (CF-IL) is for the first time constructed to load FIN for fabricating FIN CF-IL. CF-IL aims to act as carriers and cargos and enhance hair follicle (HF) co-delivery of FA and FIN for synergistic anti-alopecia. Thermal and spectroscopic analysis combined with quantum chemistry calculations and molecular dynamics confirm the formation of CF-IL. The CF-IL simultaneously increases the solubility of FA (∼648-fold) and FIN (∼686-fold), enhances the permeation and retention of FIN and FA through the follicular pathway, and promotes cellular uptake. FIN CFIL regulates the abnormal mRNA expressions in dihydrotestosterone-irritated hDPCs, and promotes hair regrowth in AGA mice in a combined manner with FIN and FA. These findings suggest that FA-based API IL is a promising approach for percutaneously co-delivering FA and FIN to HF, providing an enhanced targeting treatment for AGA.

Development of mabuterol transdermal patch: Molecular mechanism study of ion-pair improving patch stability

This paper aimed to prepare a Mabuterol (MAB) patch for treating asthma by ion-pair strategy to overcome the drug's thermal instability and elucidate the molecular mechanisms of the stabilization effect. The formulation factor, including counter-ion and pressure-sensitive adhesive (PSA), was optimized by the stability and in vitro skin permeation studies. The molecular mechanism of ion-pair stability was characterized using TGA, Raman, FT-IR, NMR, XPS, and molecular modeling. The optimized patch comprised MAB-Lactic acid (MAB-LA) and hydroxyl adhesive (AAOH) as the matrix, with Q = 126.47 ± 9.75 μg/cm2 and Fabs = 75.27%. The increased TGA (213.11 °C), disproportionation energy (ΔG = 97.44 KJ), and ion-pair lifetime (Tlife = 2.21 × 103) indicated that the counter-ion improved MAB stability through strong ionic and hydrogen bonds with LA. The remaining drug content in the MAB-LA patch was 15% higher than that of the pure MAB patch after storage for 12 months at room temperature, which was visualized by Raman imaging. The interaction between MAB-LA and AAOH PSA via hydrogen bond decreased the diffusion rate and increased the drug stability further. This study successfully developed the MAB patch, which provided a reference for applying ion-pairing strategies to improve the stability of transdermal patches.