Percutaneous Absorption Enhancement of an Ionic Molecule by Ethanol–Water Systems in Human Skin

Ethanol–water systems enhance permeation of ionic solutes through human stratum corneum. Optimum enhancement of salicylate ion permeation has been observed with ethanol volume fractions near 0.63. The mechanism of action of ethanol–water systems enhancing skin permeation was investigated by in vitro skin permeation studies combined with Fourier transform infrared spectroscopy experiments. The increased skin permeation of the ionic permeant by the ethanol–water systems may be associated with alterations involving the polar pathway. Polar pathway alterations may occur in either or both the lipid polar head and proteinaceous regions of the stratum corneum. Ion-pair formation may also contribute to increased permeation. However, the decreased permeation of salicylate ion observed at higher volume fractions of ethanol may be attributed to decreased uptake of permeant into the stratum corneum.     

曲安奈德经皮渗透特性研究

目的评价曲安奈德经皮渗透的特性。方法采用Franz扩散池法,考察药物经完整皮肤和去角质层皮肤的体外透皮能力,并采用了胶带剥离、皮肤萃取法分别获取了皮肤角质层、去角质层皮肤样本,用HPLC法测定了样本中的药物含量,考察曲安奈德在皮肤不同层的分布情况。结果曲安奈德的24 h透过量去角质层皮肤约为完整皮肤的1.6倍;8 h透皮实验,高、中、低3个浓度角质层中药物含量基本相同,真皮层则存在浓度依赖现象。结论角质层是曲安奈德的透皮吸收重要屏障,但角质层对药物的储留有饱和现象,临床上应用时需特别关注。     

渗透促进剂对盐酸普萘洛尔经皮渗透的影响

目的:研究常用渗透促进剂对盐酸普萘洛尔经皮渗透的影响。方法:采用改良Franz扩散池,以0.9%氯化钠溶液作为接收液,以增渗倍数(ER)为考察指标,考察1%、3%、5%水溶性氮酮溶液,1%、3%、5%油溶性氮酮溶液,1%水溶性氮酮丙二醇溶液,5%、10%油酸溶液,丙二醇等10种渗透促进剂对盐酸普萘洛尔透过离体大鼠腹部皮肤的影响。结果:渗透促进效果分别为3%油溶性氮酮溶液>10%油酸溶液>1%水溶性氮酮丙二醇溶液>5%油溶性氮酮溶液>1%水溶性氮酮溶液>3%水溶性氮酮溶液>1%油溶性氮酮溶液>5%水溶性氮酮溶液>5%油酸溶液>丙二醇。结论:油溶性渗透促进剂对盐酸普萘洛尔的经皮渗透促进作用有强于水溶性渗透促进剂的趋势。     

In Vitro Percutaneous Absorption of Arildone,a Highly Lipophilic Drug,and the Apparent No-Effect of the Penetration Enhancer Azone in Excised Human Skin

Purpose. Arildone, a novel lipophilic antiviral drug when evaluated in Clinical Trials showed limited skin absorption and antiviral efficacy. These studies were conducted to explain the apparent poor absorption characteristics and attempt to promote skin absorption by using Azone, a penetration enhancer. Methods. Standard in vitro skin permeation methods using excised human skin were employed to characterise the absorption of Arildone. ¹⁴C-Arildone was used to estimate the distribution in skin layers by scintigraphic and autoradiographic procedures. Results. The aqueous solubility and distribution constant values for Arildone were 2 µg ml^–1 and 5 × 10⁵ (isopropyl myristate/water), respectively. Absorption through full thickness skin or stratum corneum-viable epidermal membranes (diffusional resistant dermis removed), from a propylene glycol vehicle, was slow and the addition of Azone had no effect on the permeation rate. Distribution studies showed accumulation of Arildone in the stratum corneum. The concentration of Arildone in the viable epidermis was estimated from sectioning the skin and was found to be in sufficient amounts (400 µg cm^–3) to have potential antiviral activity. Conclusions. The apparent accumulation of Arildone in the stratum corneum suggested that the hydrophilic skin region presented the main barrier to permeation. Azone which affected the permeability of the stratum corneum was therefore not effective at enhancing Arildone absorption. Vehicles which readily permeate and enhance the transfer of lipophilic drugs from the stratum corneum into the viable epidermis were recommended.     

Percutaneous Absorption of Sunscreens Through Micro-Yucatan Pig Skin In Vitro

Purpose. The objectives of this study were to develop an in vitro model for studying sunscreen permeation in skin, and evaluate the influence of formulation differences. Methods. The sunscreens studied were two of the most widely used agents, octyl methoxycinnamate (OMC) and benzophenone-3. Preparations containing radiolabeled actives were applied to micro-Yucatan pig skin dermatomed to a thickness of 250–300 m as a finite dose in a flow-through diffusion system. At the end of each experiment the amounts removed by washing, retained inside stratum corneum (SC) and penetrated into receptor and viable skin were determined. Results. The two sunscreens reached a peak level in SC within an hour. Benzophenone-3 penetrated skin to a greater extent than OMC. The opposite was true when comparisons of SC retention were made. The ratio of retained to penetrated amount of sunscreens from a hydroalcoholic formulation at the end of 10 hours was higher when the sunscreens were present together than alone. Conclusions. Despite the highly lipophilic nature of sunscreens, particularly OMC, SC is the rate limiting skin layer for penetration. Penetration and SC retention were formulation dependent. The ratio of SC content to the amount penetrated is a useful tool for evaluating sunscreen permeation.     

Percutaneous Penetration of Acyclovir Through Excised Hairless Mouse and Rat Skin: Effect of Vehicle and Percutaneous Penetration Enhancer

The effects of vehicle and percutaneous penetration enhancer on the penetration of acyclovir through excised hairless mouse and rat skin were investigated. Four solvents, propylene glycol (PG), ethanol (ET), isopropanol (IPA), and isopropyl myristate (IPM), were employed as vehicles, in combination with four enhancers, l-farnesylazacycloheptan-2-one (7FU), l-geranylazacycloheptan-2-one (7GU), l-geranylazacyclopentan-2-one (5GU), and l-dodecylazacycloheptan-2-one (Azone). Acyclovir was suspended in vehicles to avoid the effect of the thermodynamic activity of acyclovir in the vehicle. The penetration of acyclovir through hairless mouse skin from IPA was enhanced by 7GU, whereas that from IPM was not affected. All combinations of vehicle and penetration enhancer were examined using rat skin. No effect of the enhancers was observed in the IPM vehicle. The estimated solubility parameters of vehicles and enhancers indicated that the polarities of IPM and the enhancers are similar, which prevents effective penetration of the enhancers from IPM. However, the penetration of acyclovir from the other vehicles was increased by the enhancers. The combination of hydrophilic vehicle and hydrophobic enhancer resulted in a large enhancing effect. The disappearance of the enhancers from the vehicle correlated with their enhancing activity, but other factors also seemed to affect the penetration enhancement of acyclovir.     

A Novel in Vitro Percutaneous Penetration Model: Evaluation of Barrier Properties with P-Aminobenzoic Acid and Two of Its Derivatives

Purpose The objective of this study was to evaluate the utility of a stratum corneum substitute (SCS) as a novel in vitro percutaneous penetration model. The SCS consists of synthetic stratum corneum (SC) lipids (cholesterol, free fatty acids, and specific ceramides) applied onto a porous substrate. The composition, organization, and orientation of lipids in the SCS bear high resemblance to that of the intercellular barrier lipids in SC. Methods The barrier integrity of the SCS was evaluated by means of passive diffusion studies, using three model compounds with different lipophilicities. The effects of lipid layer thickness, permeant lipophilicity, and altered lipid composition on the barrier properties were investigated, using isolated human SC as a control sample. Results For all three model compounds, the permeability characteristics of the SCS with a 12-μm-thick lipid layer closely resemble those of human SC. Modification of the lipid composition, generating an SCS that lacks the characteristic long periodicity phase as present in SC, was accompanied by a 2-fold increased permeability. Conclusions The SCS offers an attractive tool to predict solute permeation through human skin. Moreover, as its lipid composition can be modified, they may also serve as a suitable screening model for diseased skin.     

透皮促进剂对萘普生的促透效果研究

目的研究透皮促进剂月桂氮酮、油酸、月桂醇与1,2-丙二醇单独使用或混合使用对萘普生经皮渗透的促透效果。方法采用Valia-Chien双室渗透池,以10%聚乙二醇400生理盐水为接收介质,经大鼠腹部离体皮肤渗透,高效液相色谱法测定接受液中药物含量,计算药物累积透皮量和稳态透皮速率。结果 5%月桂氮酮+20%1,2-丙二醇达最大促透效果。结论脂溶性促进剂月桂氮酮、油酸,联合1,2-丙二醇使用对萘普生促透效果显著。     

不同透皮促进剂对丹参贴膏离体透皮吸收的影响

本文报道了4种透皮促进剂3％月桂氮卓酮（Azone）＋5％丙二醇，3％Azone，5％丙二醇和5％二甲基亚砜（DMSO）对丹参贴膏中两种主要有效成分丹参素和原几条醛透皮吸收的影响。采用离体鼠皮为皮肤模型，实验装置应用自行设计的单室透皮扩散池，检测方法为高效液相色谱法。结果表明，4种透皮促进剂均可不同程度地促进丹参贴膏的透皮吸收效果，其中3％Azone＋5％丙二醇组成的二元透皮促进剂作用最显著。     

不同促渗剂对蛇床子软膏透皮吸收特性的影响

目的考察不同促渗剂对蛇床子软膏透皮吸收的影响。方法采用改良Franz扩散池,以离体裸鼠皮肤为屏障,考察氮酮、油酸和高良姜油等不同种类的促渗剂对蛇床子软膏的累积渗透量、渗透吸收速率、增渗倍数等参数的影响。结果几种促渗剂对蛇床子软膏的透皮吸收均有较好的促进作用,其中以3%高良姜油效果最佳。结论高良姜油对蛇床子素经皮吸收具有显著的促进作用,为蛇床子经皮给药制剂处方设计和新药开发提供了依据。     

Physicochemical Aspects of Percutaneous Penetration and Its Enhancement

The classic diffusion model-based interpretation of percutaneous absorption is compared to a simple kinetic analysis. The physicochemical significance and the major deductions of the two approaches are shown to be in general agreement. In particular, the effect of penetrant oil/water partition coefficient on transdermal flux is consistently predicted by the two models. Diffusional and kinetic assessments of skin penetration enhancement are then shown to reveal similar dependencies upon penetrant physical chemistry. It is demonstrated that the requirements for successful promotion of a lipophilic drug's transdermal flux are quite different from those necessary for a hydrophilic penetrant. Finally, in light of published transport data and our increased comprehension of the stratum corneum barrier function, the evidence for (and significance of) different absorption paths across the stratum corneum is considered. In addition, the impact of penetrant size on transport is addressed. It is argued that currently held beliefs concerning (i) a putative polar route through the stratum corneum and (ii) the dependence of flux on molecular weight warrant considerable further attention before their unequivocal acceptance is appropriate.     

氢醌经不同皮肤层的吸收差异

目的 :评价皮肤角质层和真皮层对药物经皮吸收的差异。方法 :选择氢醌 (HQ)为模型药物 ,采用Franz吸收池法 ,考察药物经完整皮肤和剥离角质层皮肤的体外透皮能力Kp ,并比较吸收促进剂肉豆蔻酸异丙酯(IPM)共存时的促透能力大小。结果 :HQ经剥离角质层皮肤的Kp 是经完整皮肤的3 29倍 ,加入IPM后HQ的Kp 分别提高到原来的4 95倍 (经完整皮肤 )和7 49倍 (经剥离角质层皮肤 )。结论 :本实验为皮肤病态条件 ,如皮肤受伤或溃疡等时的药物经皮吸收规律研究提供了一种新的方法。     

Chitosans as Absorption Enhancers for Poorly Absorbable Drugs 2: Mechanism of Absorption Enhancement

Purpose. It has recently been shown that the absorption enhancing and toxic effects of chitosans are dependent on their chemical composition. In this study, the mechanisms underlying these effects were investigated at the cellular level. Methods. The effects on epithelial cells of chitosans with different chemical composition, absorption enhancing properties and toxicities were studied in Caco-2 monolayers. Chitosan C(l:31) has a low degree of acetylation (DA) (1%) and a low m.w. (31 kD), and displays dose-dependent absorption enhancement and cytotoxicity; chitosan C(35:170) has a higher DA (35%) and a higher m.w. (170 kD), is less dose-dependent in absorption enhancement, and is not cytotoxic. A third non-toxic chitosan C(49:22) with a high DA (49%), a low m.w. (22 kD), and no influence on epithelial permeability was used as control. Results. C(l:31) and C(35:170) bound tightly to the epithelium. Cellular uptake of the chitosans was not observed. Both chitosans increased apical but not basolateral cell membrane permeability and induced a redistribution of cytoskeletal F-actin and the tight junction protein ZO-1. This resulted in increased paracellular permeability of hydrophilic marker molecules of different molecular weights. Addition of negatively charged heparin inhibited the cellular and the absorption enhancing effects of the chitosans, indicating that these effects are mediated via their positive charges. The onset of the effects of C(35:170) on apical membrane permeability and tight junction structure was much faster than that of C(l:31). C(49:22) did not influence any of the properties of the Caco-2 cell monolayers studied. Conclusions. The binding and absorption enhancing effects of chitosans on epithelial cells are mediated through their positive charges. The interaction of chitosans with the cell membrane results in a structural reorganisation of tight junction-associated proteins which is followed by enhanced transport through the paracellular pathway.     

Comparative Analysis of Percutaneous Absorption Enhancement by d-Limonene and Oleic Acid Based on a Skin Diffusion Model

Percutaneous absorption-enhancing effects of d-limonene and oleic acid were investigated using three model drugs with different lipophilicities in in vitro diffusion experiments with guinea pig skin. Pretreatment of the skin with d-limonene resulted in a large penetration enhancement for the lipophilic butylparaben (BP) and amphiphilic 6-mercaptopurine (6-MP) but had little effect on the hydrophilic mannitol (MT). Oleic acid caused a large effect only on 6-MP penetration. The penetration profiles were analyzed with a two-layer skin diffusion model consisting of stratum corneum with polar and nonpolar routes and viable epidermis plus dermis. Through curve-fitting, six parameters corresponding to drug diffusivity and partitioning in these three regions of the skin were obtained, and the mechanisms of enhancers were assessed in comparison with those of l-geranylazacycloheptan-2-one (GACH) reported previously. Increased penetration was caused mainly by modification of the barrier property of the nonpolar route in the stratum corneum in all cases. In the nonpolar route, d-limonene increased mainly drug diffusivity, while GACH enhanced predominately drug partitioning. On the other hand, oleic acid moderately increased both parameters.     

Percutaneous Absorption and Elimination of the Penetration Enhancer Azone in Humans

The percutaneous absorption and elimination of Azone, a new penetration enhancer, were investigated in humans. The distribution and accumulation of Azone in the skin were studied by means of tape stripping. These studies reveal that pure Azone is poorly absorbed. Furthermore, what little Azone is absorbed appears to be rapidly cleared from the circulation by the kidneys. In order to explain the urinary excretion profile, the formation of at least one metabolite is suggested. No accumulation of Azone in the skin was observed.     

Effect of Vehicles and Penetration Enhancers on the In Vitro and In Vivo Percutaneous Absorption of Methotrexate and Edatrexate Through Hairless Mouse Skin

Purpose. Low-dose methotrexate (MTX) is approved for the treatment of recalcitrant rheumatoid arthritis (RA). The objective of this study was to determine the effect of vehicles and penetration enhancers on the percutaneous absorption of MTX and its analog edatrexate (EDAM), and develop transdermal (TD) delivery systems of the drugs for the treatment of RA. Methods. From previously published pharmacokinetic parameters with low-dose MTX therapy, and considering a 50 cm² diffusional area, the target steady state in vitroTD flux for MTX was calculated to be 35 g/cm²/hr. Modified Franz diffusion chambers and hairless mouse skin were used for in vitro skin permeation studies. Hairless mice were used for in vivo studies. Delivered amounts of MTX and EDAM were determined by assaying the receiver phase fluid (or blood) with validated reversed phase HPLC methods. Results. Intrinsic partition coefficient of MTX was low (log P = –1.2). Target MTX fluxes of 35 g/cm²/hr were achievable only with 1–15% (v/v) Azone^® in propylene glycol (PG). Flux of EDAM (85 g/cm²/hr) was higher than MTX from an isopropyl alcohol (IPA)—5% (v/v) Azone^® system. Clinically significant steady state in vivo blood concentration of MTX and EDAM was achieved using delivery systems containing 2.5% Azone^® in PG. Area under the drug concentration-time curves (AUC_0–24hr) for MTX were 2379 and 3534 ng*hr/ml from PG—2.5% Azone^® and PG—7.5% Azone^® systems respectively. AUC_0-24hr of EDAM was 6893 ng*hr/ml using a PG—2.5% Azone^® system. Conclusions. Results of this study show the feasibility of using a transdermal delivery system of MTX and EDAM for the treatment of rheumatoid arthritis.     

促渗剂对司来吉兰贴片透皮性能的影响

目的:考察不同质量分数的氮酮、油酸和肉豆蔻酸异丙酯3种促渗剂对司来吉兰贴片经离体豚鼠皮渗透性的影响。方法:采用Franz扩散池进行体外经皮渗透试验,利用高效液相色谱法为浓度测定方法,以不含促渗剂的司来吉兰贴片为对照计算氮酮、油酸和肉豆蔻酸异丙酯的增渗比及表观扩散系数比较促渗剂渗透效果。结果:与对照组比较,质量分数为3%的3种促渗剂增渗倍数分别为1.53、1.37和1.26,表观扩散系数分别增至2.37、1.65、1.13倍。结论:3种促渗剂均可提高司来吉兰贴片的透皮性能,其中以3%氮酮的促渗效果较好。     

Azone对安定的体外透皮促进作用

本文研究了含乙醇及丙二醇的水溶液系统中的Azone 对安定的体外透皮促进作用。发现不同浓度的Azone 溶液均可促进安定的透皮吸收,但以其0.8%的溶液作用最强,且有统计学意义。     

促渗剂对万灵五香巴布剂中麝香酮经皮渗透的影响

研究了Transcutol P、Labrasol、Labrafil M 1944、N-甲基-2-吡咯烷酮(NMP)、月桂氮(卓)酮、1,2-丙二醇等促渗剂对复方万灵五香巴布剂中麝香酮透过小鼠离体皮肤性能的影响.结果表明,月桂氮(卓)酮、NMP、Transcutol P对麝香酮有促渗作用(P＜0.05).以月桂氮(卓)酮-1,2-丙二醇-Labrasol(3:15:6)为复合促渗剂时麝香酮的透皮吸收速率最快.     

Recent knowledge: Concepts of dermal absorption in relation to skin decontamination

Skin decontamination is an important step mitigating percutaneous absorption through the stratum corneum (SC), which is also a highly complex process. Thus, understanding diffusion mechanisms and measuring dermal absorption rates are critical to protect humans from toxic exposures. Here, highly varied literature is placed in a biological and clinical perspective in regards to decontamination. Literature from PubMed and Surge Laboratory library files were searched and reviewed for relevance. Recent data have shown multiple layers of SC structural heterogeneity, which results in unique substance partitioning characteristics across the membrane. As such, attempts to model and understand this behavior in alternative in vitro membranes prove difficult. More synthetic and natural membranes are being explored as models for in vivo behavior. In addition, commonly accepted decontamination methods are undergoing risk assessment. These recent and varied literature findings update available knowledge regarding skin decontamination and its challenges, with a focus on dermal absorption. Copyright © 2015 John Wiley & Sons, Ltd.