Effects of vehicles and enhancers on transdermal delivery of melatonin

For a more effective transdermal delivery of melatonin (MT), the effects of vehicles and enhancers on its skin permeation and lag time were evaluated. Skin permeation study was conducted in Franz diffusion cells using excised hairless mouse skins. MT was analyzed by HPLC. As vehicles, ethanol (EtOH), polyethylene glycol 400 (PEG), or propylene glycol (PG) was used alone or mixed with a phosphate buffer. Binary vehicles (EtOH/buffer, PEG/buffer, PG/buffer) showed different effects on the skin permeation of MT and its lag time. Compared with the buffer alone, the PEG/buffer shortened the lag time of MT but reduced its skin permeation. EtOH/buffer significantly increased the flux of MT but prolonged the lag time with the content of EtOH. PG/buffer did not affect the lag time but slightly increased the skin permeation of MT at the higher content of PG (> or =80%). These results indicate that the composition of vehicles exerts significant influence but it per se might have limitation in modulating the transdermal delivery of MT. Next, one tested whether fatty acids could more effectively enhance the skin permeation of MT and shorten its lag time. Given the influence of vehicles on both permeation and lag time, PG was used as a vehicle for fatty acids. The permeation-enhancing effects of saturated fatty acids increased in the following order: C10>C12>C14>C16>C18. The saturated fatty acid, however, did not significantly shorten the lag time regardless of the carbon chain length. Meanwhile, similar to saturated lauric acid (C12), unsaturated oleic acid (C18) dramatically enhanced the skin permeability coefficient of MT more than 950-fold over the effect of PG alone. Moreover, oleic acid showed the shortest lag time (2.1 h). The results suggest that oleic acid in a suitable vehicle could more effectively enhance the skin permeation of MT and shorten its lag time than did the vehicles of various compositions.     

渗透促进剂对醋氯芬酸经皮渗透性的影响

目的研究醋氯芬酸溶液经离体鼠皮的透过特性,寻找能有效增加醋氯芬酸渗透的促渗剂,用以开发醋氯芬酸经皮给药传递系统。方法测定醋氯芬酸在pH 2.5、3.6、5.0、6.8、7.4 PBS缓冲液中的饱和溶解度;采用水平扩散装置进行醋氯芬酸在pH 2.5、3.6、5.0、6.8、7.4条件下及在乙醇、丙二醇、卡必醇、桉叶油醇、松节油、油酸、氮酮等促渗剂作用下的经皮渗透实验;用HPLC法分析样品。结果随着pH值的增加,醋氯芬酸的溶解度增加,经皮渗透量也呈上升趋势;氮酮、油酸和松节油均可显著增加醋氯芬酸的经皮渗透,促渗顺序为氮酮>油酸>松节油,且主要通过增加表皮基质间的分配系数实现促渗效果。结论醋氯芬酸具有一定的经皮透过性,宜制成经皮给药剂型;油酸、油溶性氮酮可作为其有效的渗透促进剂。     

Enhancement of the transdermal delivery of zidovudine by pretreating the skin with two physical enhancers: microneedles and sonophoresis

BackgroundZidovudine (AZT) has been the most widely used drug for antiretroviral therapy. In order to improve the therapy with this drug, different alternatives have been proposed, such as the transdermal administration. The use of permeation enhancers is necessary to favor the passage of this drug through the skin, due to its physicochemical properties and to the natural permeation barrier imposed by the skin. ObjectivesTo evaluate the effect of two permeation enhancers, sonophoresis and microneedles, on the permeability of AZT through the skin.MethodsPermeation studies with an AZT solution were performed using pigskin clamped in Franz-type cells. Sonophoresis was applied under different conditions (i.e., amplitude, duty cycle and application time), selected according to an experimental design, where the response variables were the increase in temperature of the skin surface and the increase in transepidermal water loss. ATR-FTIR was also used to demonstrate the effect of enhancers on membrane components. ResultsThe permeability of AZT through intact skin was very poor, with a very long lag time. Pretreatment of the skin with sonophoresis increased AZT transport significantly, reducing the lag time. The maximum flux (27.52 µgcm⁻² h⁻¹) and the highest total amount permeated (about 624 µg/cm²) were obtained when applying sonophoresis in continuous mode, with an amplitude of 20%, and an application time of 2 min. Sonophoresis appears to have an impact on stratum corneum proteins. The use of microneedles further increased the flux (30.41 µgcm⁻² h⁻¹) and the total amount permeated (about 916 µg/cm²), relative to sonophoresis. ConclusionThe results are encouraging in terms of promoting AZT transport through the skin using sonophoresis or microneedles as permeation enhancers.Graphical abstract Supplementary InformationThe online version contains supplementary material available at 10.1007/s40199-021-00402-y.     

Preparation and evaluation of aceclofenac microemulsion for transdermal delivery system

To develop novel transdermal formulation for aceclofenac, microemulsion was prepared for increasing its skin permeability. Based on solubility and phase studies, oil and surfactant was selected and composition was determined. Microemulsion was spontaneously prepared by mixing ingredients and the physicochemical properties such was investigated. The mean diameters of microemulsion were approximately 90 nm and the system was physically stable at room temperature at least for 3 months. In addition, the in vitro and in vivo performance of microemulsion formulation was evaluated. Aceclofenac was released from microemulsion in acidic aqueous medium, and dissolved amounts of aceclofenac was approximately 30% after 240 min. Skin permeation of aceclofenac from microemulsion formulation was higher than that of cream. Following transdermal application of aceclofenac preparation to delayed onset muscle soreness, serum creatine phosphokinase and lactate dehydrogenase activity was significantly reduced by aceclofenac. Aceclofenac in microemulsion was more potent than cream in the alleviation of muscle pain. Therefore, the microemulsion formulation of aceclofenac appear to be a reasonable transdermal delivery system of the drug with enhanced skin permeability and efficacy for the treatment of muscle damage.     

A combined approach of chemical enhancers and sonophoresis for the transdermal delivery of tizanidine hydrochloride

The effects of chemical enhancers and sonophoresis on the transdermal permeation of tizanidine hydrochloride (TIZ) across mouse skin were investigated. Parameters including drug solubility, apparent partition coefficient (APC), drug permeation, and degradation in skin were determined. Low frequency ultrasound was also applied in the presence and absence of chemical enhancers to assess whether drug permeation improved. APC values indicated that TIZ preferentially partitions into intercellular spaces and does not form a reservoir, with the drug also exhibiting good enzymatic stability in skin. Most of the enhancers studied significantly increased the permeation rate of TIZ through full thickness mouse skin in comparison with TIZ formulated in phosphate buffer. Maximum enhancement was observed for TIZ formulated as a suspension in 50% v/v aqueous ethanol containing 5% v/v citral. Sonophoresis significantly (p < 0.05) increased the cumulative amount of TIZ permeating through the skin at 15 and 30 min in comparison to passive diffusion. A synergistic effect was noted when sonophoresis was applied in the presence of chemical enhancers. The results suggest that the formulation of TIZ with an appropriate penetration enhancer may be useful in the development of a therapeutic system to deliver TIZ across the skin for a prolonged period, i.e. 24 hr. The application of ultrasound in association with chemical enhancers, such as the combination of 5% v/v citral in 50% v/v aqueous ethanol, could further serve as a non-oral and non-invasive drug delivery modality for the immediate therapeutic effect of muscle relaxants such as TIZ.     

Cremophor RH40-PEG 400 microemulsions as transdermal drug delivery carrier for ketoprofen

The aim of this study was to prepare novel microemulsion for transdermal drug delivery of ketoprofen (KP). The microemulsion composed of ketoprofen as model drug, isopropyl myristate (IPM) as oil phase, surfactant mixture consisting of polyoxyl 40 hydrogenated castor oil (Cremophor RH40) as surfactant and polyethylene glycol 400 (PEG400) as co-surfactant at the ratio 1:1, and water were prepared. The viscosity, droplet size, pH, conductivity of microemulsions, and skin permeation of KP through shed snake skin were evaluated. The particle size, pH, viscosity and conductivity of microemulsions were in the range of 114-210 nm, 6.3-6.8, 124-799 cPs and 1-45 μS/cm, respectively. The ratio of IPM, and surfactant mixture played the important role in the skin permeation of KP microemulsions. As the amount of surfactant mixture and IPM increased, the skin permeation of KP decreased. The formulation composed of 30% IPM, 45% surfactant mixture and 25% water showed the highest skin permeation flux. The incorporation of terpenes in the 2.5% KP microemulsions resulted in significant enhancement in skin permeation of KP. The rank order of enhancement ratio for skin permeation enhancement of terpenes was α-pinene > limonene > menthone. The results suggested that the novel microemulsion system containing IPM, water, Cremophor RH40:PEG400 and terpenes can be applied for using as a transdermal drug delivery carrier.     

Effects of cinnamene enhancers on transdermal delivery of ligustrazine hydrochloride.

Cinnamene compounds, cinnamic acid, cinnamaldehyde and cinnamic alcohol, were employed as enhancers. The effects and mechanisms of penetration promoters on the in vitro percutaneous absorption of ligustrazine hydrochloride across hairless porcine dorsal skin were investigated. Transdermal fluxes of ligustrazine hydrochloride through porcine skin were determined in vitro by Franz-type diffusion cells. The results indicated that the penetration flux of ligustrazine hydrochloride by cinnamic acid was the greatest. Significant statistical differences (P<0.05) were found between cinnamic acid and other promoters. Fourier transform-infrared (FT-IR) were carried out to analyze the effects of enhancers on the biophysical properties of the stratum corneum and the permeation enhancement mechanisms. FT-IR results revealed that the changes of peak shift and peak area due to C-H stretching vibrations in the stratum corneum lipids were associated with the selected enhancers. All of them could perturb and extract the stratum corneum lipids to different extent. Morphological changes of the skin treated with enhancers were monitored by a scanning electron microscope. It was demonstrated that the extraction of the stratum corneum lipids by the enhancers led to the disruption of stratum corneum and the desquamation of stratum corneum flake. Apparent density was newly proposed to estimate the desquamated extent of stratum corneum flake. Correlation analysis revealed that there was a linear relationship between apparent density and decrease in peak area. The results showed that the permeation enhancement mechanisms of cinnamene were pleiotropic ones, including disordering the lipids, extracting the lipids and competitive hydrogen bonding between cinnamene enhancers and amides of ceramide head groups in stratum corneum.     

Effects of dimethylformamide and L-menthol permeation enhancers on transdermal delivery of quercetin

In this work a feasibility study of transdermal delivery system for quercertin (Q) in carbopol gel through abdominal hairless pig skin in vitro was performed. Dimethylformamide (DMF) and L-menthol (M) were selected as enhancers. Permeation experiences were carried out by using Franz-type diffusion cells. Phosphate saline buffer (pH 7.4) was used in the receptor compartments. All the system was maintained at 32 +/- 0.5 degrees C with a circulating water jacket and magnetic stirring (180 rpm). Samples were analysed by UV-VIS spectrophotometer at 255 nm. Flux (Jm) values, permeation (P) and diffusion (D) coefficients were obtained. Results of Q in CG permeation experiences with different percentages of DMF and M showed that 16.7% DMF and 1.95% L-menthol enhancers were the best quantities for the system tested. Enhancer effect can be attributed to direct action on membrane structure by promoting its distension. Therefore, enhancer substitutes for water in pores, improving active principal permeation through pig skin. M significantly increases Q permeation about 17 times higher than control. The results of permeation experiments with M and DMF using the same enhancer concentration (1.42%) conclude that M action is 9 times higher than DMF, approximately, indicating that M is an effective enhancer for a transdermal therapeutic system of Q in CG as vehicle.     

Effects of enantiomer and isomer permeation enhancers on transdermal delivery of ligustrazine hydrochloride

Enantiomers and isomers, such as D-limonene, L-limonene, and alpha-terpinene, were selected as enhancers. The effects and mechanisms of penetration enhancers on in vitro transdermal delivery of ligustrazine hydrochloride (LH) across hairless porcine dorsal skin were investigated. Transdermal fluxes of LH through porcine skin were determined in vitro by Franz-type diffusion cells. D-limonene, L-limonene, and alpha-terpinene could significantly promote the transdermal fluxes of LH, but no statistical difference (p > 0.05) between them was found. The lag time of L-limonene and alpha-terpinene were 2.55 and 2.20 times compared with that of D-limonene. Fourier transform-infrared (FTIR) was carried out to analyze the effects of enhancers on the biophysical natures of the stratum corneum (SC) and the permeation enhancement mechanism. FTIR spectra revealed that the changes of peak shift and peak area due to C-H stretching vibrations in the SC lipids were associated with the selected enhancers. All of them could perturb and extract the SC lipids to different extent and L-limonene showed obvious changes. Morphological changes of the skin treated with enhancers were monitored by a scanning electron microscope (SEM). The extraction of the SC lipids by the enhancers led to the disruption of SC and the desquamated SC flake. Apparent density (AD) was newly proposed to estimate the desquamated extent of SC flake. The results showed that the enantiomers and isomers enhanced the permeation of LH by pleiotropic mechanisms.     

经皮给药系统促渗方法研究的新进展

促渗方法的发展对于经皮给药的研究意义重大。笔者从化学促渗技术，包括化学促渗剂、前体药物、传递体、含醇脂质体、非离子表面活性剂脂质体和微乳；以及物理促渗技术，包括离子导入、电致孔、超声波促渗、微针、照相波、热致孔和磁场导入等诸多方面综述了近年来经皮给药促渗方法研究的新进展。     

透皮吸收促进剂在经皮给药系统中的质控和评价方法

透皮吸收制剂是国际上第三代药物制剂的研究重点领域。透皮吸收促进剂在处方中的合理应用和质量控制及其评价方法日益重要。通过对透皮促进机理、协同作用等的探讨,介绍透皮吸收促进剂的选用原则,并对透皮给药制剂和局部用药局部起效的皮肤外用制剂处方中使用的要求加以讨论,介绍了现有的评价方法和基本的技术要求。     

Novel transdermal delivery of Timolol maleate using sugar esters: Preclinical and clinical studies

The feasibility of matrix controlled transdermal patch based on sugar fatty acid ester (SE) as penetration and absorption enhancer containing Timolol maleate (TM) was investigated. The influence of fatty acid type, chain length and hydrophile-lipophile balance (HLB) on the in vitro drug release as well as its permeation across hairless rat skin were studied and compared aiming to select a patch formula for clinical performance. Skin irritation induced by SE patch was evaluated by visual scoring, color reflectance measurements and non-invasive transepidermal water loss (TEWL) technique. The results indicated that among different SEs tried, laurate SE with shorter fatty acid chain length and higher HLB value significantly increased the amount of TM liberated from the patch (99 ± 2.1%) and its permeation across rat skin (86 ± 4.3%). The total drug permeation and flux values were approximately 5-fold greater compared to SE free patch. The extent of absorption of TM-SE patch expressed by AUC was 64% larger as compared to the oral solution with steady plasma concentration over 18 h and relative bioavailability (F_rel) of 163%. The developed patch was well tolerated by all the subjects with only moderate skin irritation, which was recovered in 24 h after patch removal. The results are very encouraging and offer an alternative approach to maintain higher, prolonged and controlled blood level profile of the drug over 18-24 h.     

Microneedle/nanoencapsulation-mediated transdermal delivery: Mechanistic insights

A systematic study was undertaken to gain more insight into the mechanism of transdermal delivery of nanoencapsulated model dyes across microneedle (MN)-treated skin, a complex process not yet explored. Rhodamine B (Rh B) and fluorescein isothiocyanate (FITC) as model hydrophilic and hydrophobic small/medium-size molecules, respectively, were encapsulated in poly lactic-co-glycolic acid (PLGA) nanoparticles (NPs) and delivered through full thickness porcine skin pretreated with MN array. Permeation through MN-treated skin was affected by physicochemical characteristics of NPs and the encapsulated dyes. Dye flux was enhanced by smaller particle size, hydrophilicity, and negative zeta potential of NPs. Regarding encapsulated dyes, solubility at physiological pH and potential interaction with skin proteins proved to outweigh molecular weight as determinants of skin permeation. Data were verified using confocal laser scanning microscopy imaging. Findings coupled with the literature data are supportive of a mechanism involving influx of NPs, particularly of smaller size, deep into MN-created channels, generating depot dye-rich reservoirs. Molecular diffusion of the released dye across viable skin layers proceeds at a rate determined by its molecular characteristics. Data obtained provide mechanistic information of importance to the development of formulation strategies for more effective intradermal and transdermal MN-mediated delivery of nanoencapsulated therapeutic agents.     

促渗剂对奥沙普秦经皮渗透的促进作用

目的：考察几种促渗剂对奥沙普秦透皮作用的影响。方法：采取改良Franz直立式释放池,以离体小鼠皮肤为透皮屏障,计算含不同浓度和组合促透剂的奥沙普秦的累积渗透量Q及渗透速率K,结果;含不同促渗剂奥沙普秦的透皮速率有明显差别,其促进强度依次为油酸＞月桂氮Chuo酮＞薄荷脑;混合促渗剂的促渗效果均比单用时有不同程度的提高;丙二醇有明显的抑制作用,并且抑制油酸,月桂氮Chuo酮及薄荷脑的促渗作用。结论：奥沙普秦透皮吸收符合非极性通道释放的零级动力学方程,其中以10％油酸加1％月桂氮Chuo酮组成的混合促进剂作用最显著。     

In vitro permeation study of hinokitiol: effects of vehicles and enhancers

In vitro permeation of hinokitiol (HKL) through hairless mouse skin was investigated using a diffusion cell. Either propylene glycol (PG) or ethanol (EtOH) was used as a vehicle for HKL. After applying the HKL solutions of 0.5%. 1%, 2%, and 5% onto the skin, the amount of HKL transferred through the skin into the receptor solution, phosphate-buffered saline (PBS, pH7.4), was determined at a predetermined time intervals for 18 hr using a high performance chromatography (HPLC). EtOH was more effective than PG in terms of in vitro permeation of HKL. This is possibly because EtOH acts as a permeation enhancer. Another reason would be related to the higher thermodynamic activity of HKL in ethanol. To investigate the effect of an enhancer on the in vitro permeation, oleyl alcohol, 1-dodecyl-2-pyrrolidone (DP), and lauric acid were used as enhancers. Each was added to the HKL solution (1%) so that the concentration of the enhancer was 1%. Among the enhancers, DP was the most effective and it enhanced the permeation of HKL approximately 5-10 times.     

不同促渗剂对盐酸氨酮戊酸原位凝胶体外透皮吸收的影响

目的：研究不同透皮促渗剂对盐酸氨酮戊酸原位凝胶体外透皮吸收的影响,为筛选最佳透皮促渗剂提供实验依据。方法：采用Franz扩散池法,以离体大鼠皮肤为模型,选择3种常用透皮促渗剂月桂氮芯卓酮（azone,AZ）、丙二醇（propylene glycol,PG）、二甲亚砜（dimethyl sulfoxide,DMSO）,分别考察单一促渗剂及二元促渗剂对盐酸氨酮戊酸原位凝胶体外透皮吸收的影响。结果：含促渗剂盐酸氨酮戊酸原位凝胶体外透皮吸收显著高于未添加促渗剂盐酸氨酮戊酸原位凝胶及市售制剂;采用单一促渗剂时,1% PG促渗效果最好;采用二元促渗剂时,3% AZ+1% PG促渗效果最好;3% AZ+1% PG促渗效果优于1% PG,含促渗剂3% AZ+1% PG的盐酸氨酮戊酸原位凝胶透皮性优于市售制剂艾拉。结论：添加促渗剂的方法能够显著改善盐酸氨酮戊酸的体外透皮吸收性,3% AZ+1% PG构成的二元促渗剂用于盐酸氨酮戊酸原位凝胶促渗效果最佳;本研究为设计优良的盐酸氨酮戊酸经皮给药系统药物奠定了重要基础。     

Skin Permeation Enhancement of Diclofenac by Fatty Acids

This study systematically investigated the enhancing effect of fatty acids on the skin permeation of diclofenac. The fatty acids were evaluated in terms of their carbon-chain length, the degree of unsaturation, and their functional groups. The rat-skin permeation rates of diclofenac, saturated in propylene glycol (PG) containing 1% (w/v) fatty acid, were determined using the Keshary-Chien diffusion cells at 37°C. The effect of fatty acids on the saturated solubility of diclofenac in PG was also determined at 37°C using high-performance liquid chromatography. Among the saturated fatty acids tested, palmitic acid (C16:0) showed the most potent skin permeation-enhancing effect. A parabolic correlation was observed between the enhancement effect and the fatty acid carbon-chain length among these saturated fatty acids of C12–C20 units. For the monounsaturated fatty acid series, an increase in permeation was observed as the carbon-chain length increased, and oleic acid (C18:1) showed the highest permeation-enhancing effect. Increasing the number of double bonds in the octadecanoic acids resulted in a parabolic effect in the permeation of diclofenac, revealing oleic acid as the most effective enhancer used in this study. When the carboxylic acid moiety of oleic acid was changed to an amide (oleamide) or hydroxyl (oleyl alcohol) group, a decrease in permeation activity was observed. These results, therefore, suggest that the cis-monounsaturated configuration and the carboxylic acid moiety of an 18-carbon unit fatty acid in PG are the optimum requirements for the effective skin permeation of diclofenac.     

Investigating the potential of essential oils as penetration enhancer for transdermal losartan delivery: Effectiveness and mechanism of action

The effect of tea tree oil (TTO), cumin oil (CO), rose oil (RO) and aloe vera oil (AVO) on the skin permeation of losartan potassium (LP) was investigated. In vitro skin permeation studies were carried out using rat skin. The mechanism of skin permeation enhancement of LP by essential oils treatment was evaluated by FTIR, DSC, activation energy measurement and histopathological examination. Both concurrent ethanol/enhancer treatment and neat enhancer pretreatment of rat SC with all the oils produced significance increase in the LP flux over the control. The effectiveness of the oils as the penetration enhancers was found to be in the following descending order: AVO > RO > CO > TTO. However, only AVO was the only enhancer to provide target flux required to deliver the therapeutic transdermal dose of LP. FTIR and DSC spectra of the enhancer treated SC indicated that TTO, CO, RO and AVO increased the LP permeation by extraction of SC lipids. The results of thermodynamic studies and histopathological examination of AVO treated SC suggested additional mechanisms for AVO facilitated permeation i.e. transient reduction in barrier resistance of SC and intracellular transport by dekeratinization of corneocytes which may be attributed to the presence of triglycerides as constituents of AVO. It is feasible to deliver therapeutically effective dose of LP via transdermal route using AVO as penetration enhancer.     

Transdermal and dermal delivery of adefovir: Effects of pH and permeation enhancers

The objective of this work was to investigate feasibility of transdermal and dermal delivery of adefovir (9-(2-phosphonomethoxyethyl)adenine), a broad-spectrum antiviral from the class of acyclic nucleoside phosphonates. Transport of 2% adefovir through and into porcine skin and effects of various solvents, pH, and permeation enhancers were studied in vitro using Franz diffusion cell. From aqueous donor samples, adefovir flux through the skin was 0.2-5.4 microg/cm2/h with greatest permeation rate at pH 7.8. The corresponding adefovir skin concentrations reached values of 120-350 microg/g of tissue. Increased solvent lipophilicity resulted in higher skin concentration but had only minor effect on adefovir flux. A significant influence of counter ions on both transdermal and dermal transport of adefovir zwitterion was observed at pH 3.4. Permeation enhancer dodecanol was ineffective, 1-dodecylazepan-2-one (Azone) and dodecyl 2-(dimethylamino)propionate (DDAIP) showed moderate activity. The highest adefovir flux (11.3+/-3.6 microg/cm2/h) and skin concentration (1549+/-416 microg/g) were achieved with 1% Transkarbam 12 (5-(dodecyloxycarbonyl)pentylammonium 5-(dodecyloxycarbonyl)pentylcarbamate) at pH 4. This study suggests that, despite its hydrophilic and ionizable nature, adefovir can be successfully delivered through the skin.     

皮肤给药的经皮吸收与测量技术研究进展

经皮给药系统（TDDS）可避免首关效应、胃肠道破坏，为新型皮肤给药系统，可通过控制释放而延长治疗效果，成为药物制剂开发研究的热点之一。但是，药物的理化性质以及皮肤屏障影响药物的经皮吸收。综述了TDDS常用的促渗透技术，包括化学、物理、纳米、天然促渗透技术；介绍了促渗透能力的测定方法，包括体外、离体和体内评估皮肤渗透性的方法。通过对经皮药物递送系统和经皮吸收能力测定方法的归纳与总结，以期为TDDS的合理使用和快速发展提供参考。