Effect of Different Pressure-Sensitive Adhesives on Performance Parameters of Matrix-Type Transdermal Delivery Systems

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.

Water-compatible cross-linked pyrrolidone acrylate pressure-sensitive adhesives with persistent adhesion for transdermal delivery: Synergistic effect of hydrogen bonding and electrostatic force

Poor skin adhesion and mechanical properties are common problems of pressure-sensitive adhesive (PSA) in transdermal drug delivery system (TDDS). Its poor water compatibility also causes the patch to fall off after sweating or soaking in the application site. To solve this problem, poly (2-Ethylhexyl acrylate-co-N-Vinyl-2-pyrrolidone-co-N-(2-Hydroxyethyl)acrylamide) (PENH), a cross-linked pyrrolidone polyacrylate PSA, was designed to improve the adhesion and water resistance of PSA through electrostatic force and hydrogen bonding system. The structure of PENH was characterized by 1H NMR, FTIR, DSC, and other methods. The mechanism was studied by FTIR, rheological test, and molecular simulation. The results showed that the PENH patch could adhere to human skin for more than 10 days without cold flow, and it could still adhere after sweating or water contact. In contrast, the commercial PSA Duro-Tak® 87-4098 and Duro-Tak® 87-2852 fell off completely on the 3rd and 6th day, respectively, and Duro-Tak® 87-2510 showed a significant dark ring on the second day. Mechanism studies have shown that the hydrogen bond formed by 2-ethylhexyl acrylate (2-EHA), N-vinyl-2-pyrrolidinone (NVP), and N-(2-Hydroxyethyl)acrylamide (HEAA) enhances cohesion, the interaction with skin improves skin adhesion, and the electrostatic interaction with water or drug molecules enhances the ability of water absorption and drug loading. Due to the synergistic effect of hydrogen bonds and electrostatic force, PENH can maintain high cohesion after drug loading or water absorption. PENH provides a choice for the development of water-compatible patches with long-lasting adhesion. STATEMENT OF SIGNIFICANCE: Based on the synergistic effect of hydrogen bonding and electrostatic force, a hydrogen-bonded, cross-linked pyrrolidone acrylate pressure-sensitive adhesive for transdermal drug delivery was designed and synthesized, which has high adhesion and cohesive strength and is non-irritating to the skin. The patch can be applied on the skin surface continuously for more than 10 days without the phenomenon of "dark ring", and the patch can remain adherent after the patient sweats or bathes. This provides a good strategy for choosing a matrix for patches that require prolonged administration.

Permeation-Enhancing Strategies for Transdermal Delivery of Cannabinoids

Introduction: This review aims to provide an overview of the advancements and status of clinical studies and potential permeation-enhancing strategies in the transdermal delivery of cannabinoids. Methods: A systematic and comprehensive literature search across academic databases, search engines, and online sources to identify relevant literature on the transdermal administration of cannabinoids. Results: Cannabinoids have proven beneficial in the treatment of wide-ranging physical and psychological disorders. A shift toward legalized cannabinoid products has increased both interests in cannabinoid research and the development of novel medicinal exploitations of cannabinoids in recent years. Oral and pulmonary delivery of cannabinoids has several limitations, including poor bioavailability, low solubility, and potential side effects. This has diverted scientific attention toward the transdermal route, successfully overcoming these hurdles by providing higher bioavailability, safety, and patient compliance. Yet, due to the barrier properties of the skin and the lipophilic nature of cannabinoids, there is a need to increase the permeation of the drugs to the underneath layers of skin to reach desired therapeutic plasma levels. Literature describing detailed clinical trials on cannabinoid transdermal delivery, either with or without permeation-enhancing strategies, is limited. Conclusion: The limited number of reports indicates that increased attention is needed on developing and examining efficient transdermal delivery systems for cannabinoids, including patch design and composition, drug-patch interaction, clinical effectiveness and safety in vivo, and permeation-enhancing strategies.

Innovative Topical Patches for Non-Melanoma Skin Cancer: Current Challenges and Key Formulation Considerations

Non-melanoma skin cancer (NMSC) is the most prevalent malignancy worldwide, with approximately 6.3 million new cases worldwide in 2019. One of the key management strategies for NMSC is a topical treatment usually utilised for localised and early-stage disease owing to its non-invasive nature. However, the efficacy of topical agents is often hindered by poor drug penetration and patient adherence. Therefore, various research groups have employed advanced drug delivery systems, including topical patches to overcome the problem of conventional topical treatments. This review begins with an overview of NMSC as well as the current landscape of topical treatments for NMSC, specifically focusing on the emerging technology of topical patches. A detailed discussion of their potential to overcome the limitations of existing therapies will then follow. Most importantly, to the best of our knowledge, this work unprecedentedly combines and discusses all the current advancements in innovative topical patches for the treatment of NMSC. In addition to this, the authors present our insights into the key considerations and emerging trends in the construction of these advanced topical patches. This review is meant for researchers and clinicians to consider utilising advanced topical patch systems in research and clinical trials toward localised interventions of NMSC.

Design, Development, and Evaluation of Treprostinil Embedded Adhesive Transdermal Patch

Clinical application of treprostinil in pulmonary arterial hypertension is hampered by adverse effects caused by its high dosing frequency. The objective of this investigation was to Formulate an adhesive-type transdermal patch of treprostinil and evaluate it both in vitro and in vivo. A 3²-factorial design was utilized to optimize the selected independent variables (X₁: drug amount, X₂: enhancer concentration) on the response variables (Y₁: drug release, Y₂: transdermal flux). The optimized patch was evaluated for various pharmaceutical properties, skin irritation, and pharmacokinetics in rats. Optimization results signify considerable influence (p < 0.0001) of X₁ on both Y₁ and Y₂, as compared to X₂. The optimized patch possesses higher drug content (>95%), suitable surface morphology, and an absence of drug crystallization. FTIR analysis revealed compatibility of the drug with excipients, whereas DSC thermograms indicate that the drug exists as amorphous in the patch. The adhesive properties of the prepared patch confirm adequate adhesion and painless removal, while the skin irritation study confirms its safety. A steady drug release via Fickian diffusion and greater transdermal delivery (~23.26 µg/cm²/h) substantiate the potential of the optimized patch. Transdermal therapy resulted in higher treprostinil absorption (p < 0.0001) and relative bioavailability (237%) when compared to oral administration. Overall, the results indicate that the developed drug in the adhesive patch can effectively deliver treprostinil through the skin and could be a promising treatment option for pulmonary arterial hypertension.

Influence of Acid-Modified Clinoptilolite on the Self-Adhesive Properties of Silicone Pressure-Sensitive Adhesives

The preparation of a new "eternally alive adhesive" based on silicone pressure-sensitive adhesives with clinoptilolite is presented. Neat and acid-modified (i.e., treated with sulfuric acid (VI)) clinoptilolite was used. The effect of clinoptilolite acid treatment on the adhesive properties of pressure-sensitive adhesive tapes was tested. The obtained tapes exhibited increased thermal resistance when compared to the reference tapes. Despite introducing the filler, the pressure-sensitive adhesive tapes maintained good functional properties. The new self-adhesive materials show promising implementation potential where increased thermal resistance is required.

Fabrication of Polymeric Microneedles using Novel Vacuum Compression Molding Technique for Transdermal Drug Delivery

PURPOSE

To demonstrate the feasibility of vacuum compression molding as a novel technique for fabricating polymeric poly (D, L-lactic-co-glycolic acid) microneedles.

METHODS

First, polydimethylsiloxane molds were prepared using metal microneedle templates and fixed in the MeltPrep® Vacuum Compression Molding tool. Poly (D, L-lactic-co-glycolic acid) (EXPANSORB® DLG 50-5A) was added, enclosed, and heated at 130°C for 15 min under a vacuum of -15 psi, cooled with compressed air for 15 min, followed by freezing at -20°C for 30 min, and stored in a desiccator. The microneedles and microchannels were characterized by a variety of imaging techniques. In vitro permeation of model drug lidocaine as base and hydrochloride salt was demonstrated across intact and microporated dermatomed human skin.

RESULTS

Fabricated PLGA microneedles were pyramid-shaped, sharp, uniform, and mechanically robust. Scanning electron microscopy, skin integrity, dye-binding, histology, and confocal laser microscopy studies confirmed the microchannel formation. The receptor delivery of lidocaine salt increased significantly in microporated (270.57 ± 3.73 μg/cm²) skin as compared to intact skin (142.19 ± 13.70 μg/cm²) at 24 h. The receptor delivery of lidocaine base from microporated skin was significantly higher (312.37 ± 10.57 μg/cm²) than intact skin (169.68 ± 24.09 μg/cm²) up to 8 h. Lag time decreased significantly for the base (2.24 ± 0.17 h to 0.64 ± 0.05 h) and salt (4.76 ± 0.31 h to 1.47 ± 0.21 h) after microporation.

CONCLUSION

Vacuum compression molding was demonstrated as a novel technique to fabricate uniform, solvent-free, strong polymer microneedles in a short time.

Formulation and Evaluation of a Drug-in-Adhesive Patch for Transdermal Delivery of Colchicine

Gout is one of the most prevalent rheumatic diseases, globally. Colchicine (COL) is the first-line drug used for the treatment of acute gout. However, the oral administration of COL is restricted, owing to serious adverse reactions. Therefore, this study aimed to develop a drug-in-adhesive (DIA) patch to achieve transdermal delivery of COL. We investigated the solubility of COL in different pressure-sensitive adhesives (PSAs) using slide crystallization studies. The COL-DIA patches were optimized based on in vitro skin penetration studies and evaluated by in vivo pharmacokinetics and pharmacodynamics. The results showed that the optimized COL-DIA patch contained 10% COL, Duro-Tak 87-2516 as PSA, 5% oleic acid (OA) and 5% propylene glycol (PG) as permeation enhancer, exhibiting the highest in vitro cumulative penetration amount of COL (235.14 ± 14.47 μg∙cm^-2 over 48 h). Pharmacokinetic studies demonstrated that the maximum plasma drug concentration (C_max) was 2.65 ± 0.26 ng/L and the mean retention time (MRT) was 37.47 ± 7.64 h of the COL-DIA patch, effectively reducing the drug side effects and prolonging drug activity. In addition, pharmacodynamic studies showed the patch significantly decreased the expression levels of inflammatory factors of gouty rats and reduced pathological damage in the ankle joint of rats, making it an attractive alternative to the administration of COL for the treatment of gout.

Development and evaluation of a drug-in-adhesive transdermal delivery system for delivery of olanzapine

OBJECTIVES

Olanzapine (OZP) is a safe and effective atypical antipsychotic drug used in treating schizophrenia and bipolar disorders. The dosage forms currently on the market for OZP are administered via oral or intramuscular routes. However, there are many problems associated with oral and intramuscular routes of drug administration. Thus, our aim was to develop a drug-in-adhesive transdermal delivery system (TDS) that can deliver OZP for 3 days.

METHODS

We determined passive permeation, effect of oleic acid as chemical enhancer, and delivery of OZP across different skin types. Based on preliminary studies and saturation solubility of OZP in different pressure-sensitive adhesives (PSAs), we formulated and characterized solution-based TDS in acrylate PSA and suspension-based TDS in silicone and PIB PSA, with oleic acid as chemical enhancer.

RESULTS

Acrylate solution-based TDS, silicone, and PIB suspension-based TDS delivered 58.97 ± 6.59 µg/sq.cm, 129.34 ± 16.59 µg/sq.cm, and 245.00 ± 2.51 µg/sq.cm, respectively, using in vitro permeation testing. PIB PSA suspension-based TDS met the 3 days desired target delivery. Skin irritation testing using In vitro EpiDerm^TM skin irritation test (EPI-200-SIT) kit found PIB TDS to be nonirritant.

CONCLUSION

The PIB PSA suspension-based TDS could serve as a potentially effective transdermal delivery system for olanzapine.

Influence of Silicone Additives on the Properties of Pressure-Sensitive Adhesives

Research was carried out on the influence of various silicone compounds on the properties of pressure-sensitive adhesives. Silicone-based pressure-sensitive adhesives have good self-adhesive properties and are used in many different industries. However, their thermal resistance is relatively low. In order to improve this property, modifications were made to these adhesives. Compositions were tested, such as viscosity or thermogravimetric analysis, as well as tests of finished products in the form of self-adhesive tapes, i.e., peel adhesion, tack, cohesion at room and elevated temperature, SAFT test (Shear Adhesive Failure Temperature), pot-live (viscosity) and shrinkage. During the tests, an increase in thermal resistance (225 °C), lower shrinkage (0.08%), and lower viscosity was achieved (16.5 Pas), which is a positive phenomenon in the technology of pressure-sensitive adhesives. Thanks to this research, the properties of silicone self-adhesive adhesives have been significantly improved.

Microscopic and Spectroscopic Imaging and Thermal Analysis of Acrylates, Silicones and Active Pharmaceutical Ingredients in Adhesive Transdermal Patches

Dermal or transdermal patches are increasingly becoming a noteworthy alternative as carriers for active pharmaceutical ingredients (APIs), which makes their detailed physicochemical evaluation essential for pharmaceutical development. This paper demonstrates mid-infrared (FTIR) and Raman spectroscopy with complementary microscopic methods (SEM, optical and confocal Raman microscopy) and differential scanning calorimetry (DSC) as tools for the identification of the state of model API (testosterone TST, cytisine CYT or indomethacin IND) in selected adhesive matrices. Among the employed spectroscopic techniques, FTIR and Raman may be used not only as standard methods for API identification in the matrix, but also as a means of distinguishing commercially available polymeric materials of a similar chemical structures. A novel approach for the preparation of adhesive polymers for the FTIR analysis was introduced. In silicone matrices, all three APIs were suspended, whereas in the case of the acrylic PSA, Raman microscopy confirmed that only IND was dissolved in all three acrylic matrices, and the dissolved fraction of the CYT differed depending on the matrix type. Moreover, the recrystallization of TST was observed in one of the acrylates. Interestingly, a DSC analysis of the acrylic patches did not confirm the presence of the API even if the microscopic images showed suspended particles.

Microneedle and iontophoresis mediated delivery of methotrexate into and across healthy and psoriatic skin

Psoriasis is a condition of the skin which involves scales, dry patches, and inflammation. Methotrexate (logP: -1.8, MW:454.44 g/mol) is administered orally or intravenously to treat psoriasis. The first-pass metabolism and systemic toxicity can be avoided by administration via skin. Topical and transdermal delivery of methotrexate using iontophoresis and microneedles, alone and in combination was investigated using full-thickness healthy human skin. It is also equally relevant to evaluate the delivery into and across damaged/diseased skin. Hence, this study investigated the delivery of methotrexate using ex vivo healthy and psoriatic human skin to understand the effect of skin disease condition on delivery of methotrexate via skin. A lower resistance and a higher TEWL for psoriatic skin indicated damaged barrier function, while histology studies indicated epithelial hyperproliferation and elongated rete ridges. Using the optimized iontophoretic parameters, there was no significant difference in receptor delivery for psoriatic skin (39.51 ± 4.45 µg/sq.cm) as compared to healthy skin (43.15 ± 0.83 µg/sq.cm). However, methotrexate delivery into psoriatic skin (126.23 ± 24.65 µg/sq.cm) was significantly higher as compared to healthy skin (12.02 ± 4.89 µg/sq.cm). Thus, significantly higher total delivery was observed from psoriatic skin than healthy skin.

Formulation, Preparation, Characterization, and Evaluation of Dicarboxylic Ionic Liquid Donepezil Transdermal Patches

Donepezil (DPZ) is generally administered orally to treat Alzheimer’s disease (AD). However, oral administration can cause gastrointestinal side effects. Therefore, to enhance compliance, a new way to deliver DPZ from transdermal patch was developed. Ionic bonds were created by dissolving dicarboxylic acid and DPZ in ethanol, resulting in a stable ionic liquid (IL) state. The synthesized ILs were characterized by differential scanning calorimetry, optical microscope, Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. The DPZ ILs were then transformed to a suitable drug-in-adhesive patch for transdermal delivery of DPZ. The novel DPZ ILs patch inhibits crystallization of the IL, indicating coherent design. Moreover, DPZ ILs and DPZ IL patch formulations performed excellent skin permeability compared to that of the DPZ free-base patch in both in vitro and ex vivo skin permeability studies.

Effect of plasticizers on drug-in-adhesive patches containing 5-fluorouracil

Topical patches containing 5-fluorouracil (5-FU) are a feasible alternative to overcome the shortcomings of commercial cream for the treatment of non-melanoma skin cancer (NMSC). Plasticizers are a critical component of drug-in-adhesive (DIA) patches as they can significantly affect the mechanical, adhesive and drug release characteristics of the patches. Eudragit® E (EuE) is a methacrylate-based cationic copolymer capable of producing flexible and adhesive films for topical application. In this study, the effect of plasticizers on the mechanical, adhesive and 5-FU release characteristics of EuE-based patches was comprehensively evaluated. While the elongation at break (%) and adhesion of the films were significantly increased with increasing triacetin, dibutyl sebacate (DBS) and triethyl citrate (TEC) concentrations, the tensile strength showed an inverse relationship. EuE plasticized with 40% triacetin, 30% DBS or 40% w/w TEC produced elastic and adhesive films most suitable for topical application. In vitro release studies of the 5-FU-loaded patches demonstrated an initial burst release pattern during the first 10 min followed by a slow release over 120 min. In summary, this study provides important information on effect of plasticizers for preparation of EuE-based patches with desired mechanical, adhesive and release characteristics of 5-FU towards their potential application in the treatment of NMSC.

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.

Impact of Different Mixing Methods on the Performance of Suspension-Based Transdermal Delivery Systems

Suspension-based matrix transdermal delivery systems (TDSs) are specialized systems that maintain a continuous driving force for drug delivery over prolonged wear. The pressure-sensitive adhesive (PSA) is the most critical constituent of such systems. Our study aimed to determine the effect of different mixing methods on the performance of silicone PSA-based suspension TDSs. Lidocaine suspension TDSs were prepared using conventional slow rotary mixing, high-speed homogenization, bead-mill homogenization, vortex shaking, and by an unguator. Resultant TDSs were tested for tack, shear, and peel properties and correlated to coat weight, content uniformity, microstructure, and in vitro permeation across dermatomed human skin. Every mixing method tested caused a significant reduction in peel. However, bead-mill homogenization resulted in significant loss of all adhesive properties tested, while unguator-mixed TDSs retained most properties. Good linear correlation (R² = 1.000) between the shear properties of the TDSs with the average cumulative amount of lidocaine permeated after 24 h was observed, with no significant difference between percutaneous delivery from slow rotary-mixed systems (1334 ± 59.21 μg/cm²) and unguator-mixed systems (1147 ± 108.3 μg/cm²). However, significantly lower delivery from bead-mill homogenized systems (821.1 ± 28.00 μg/cm²) was noted. While many factors affect TDS performance, careful consideration must also be given to the processing parameters during development as they have been shown to affect the resultant system's therapeutic efficacy. Extensive mixing with bead-mill homogenization demonstrated crystallization of drug, loss in adhesive properties, coat weight, and film thickness, with reduced transdermal delivery of lidocaine from the prepared system.

Active Bio-Based Pressure-Sensitive Adhesive Based Natural Rubber for Food Antimicrobial Applications: Effect of Processing Parameters on Its Adhesion Properties

A novel active bio-based pressure-sensitive adhesive incorporating cinnamon oil (Bio-PSA/CO) obtained from the mixture of natural rubber (NR), xyloglucan (XG), and cinnamon oil (CO) for food antimicrobial applications were successfully developed by using a two-roll mill mixer. The effect of the main process factors (i.e., nip gap and mastication time) and XG content on the adhesion properties of the obtained PSA were investigated with different coated substrates including kraft paper, nylon film, polypropylene (PP) film, and aluminum foil (Al). The results suggested that the developed NR-PSA/CO could be applied well to all types of substrate materials. Peel strength and shear strength of the NR-PSA/CO with all substrate types were in the ranges of ~0.03 × 10²–5.64 × 10² N/m and ~0.24 × 10⁴–9.50 × 10⁴ N/m², respectively. The proper processed condition of the NR-PSA/CO was represented with a nip gap of 2 mm and a mastication time of 15 min. An increase in XG content up to 40–60 phr can improve the adhesion properties of the adhesive. The resulting material could be used as an active sticky patch to extend the shelf-life of food in a closed packaging system. The shelf-life of the food samples (banana cupcake) could be extended from 4 to 9 days with NR-PSA/CO patch.