Effect of penetration enhancers on the permeation of mannitol, hydrocortisone and progesterone through human skin

Mannitol, hydrocortisone and progesterone were selected as model penetrants to assess the mode of action of eight potential penetration enhancers in human skin. Their partition coefficients, octanol: water and stratum corneum: water were measured and correlated with their postulated routes of penetration through human skin. The results suggest that mannitol penetrated via a polar route, hydrocortisone by a mainly lipid route and progesterone via a lipid pathway but its penetration rate was probably affected by aqueous layers. From permeation studies through cadaver skin in which an in-vivo mimic method was used, it was concluded that the penetration enhancers fell into three main categories: solvents which enhanced permeation of polar and non-polar compounds e.g. 2-pyrrolidone, N-methylpyrrolidone, N-methylformamide and propylene glycol plus Azone; enhancers which preferentially affected the polar route e.g. propylene glycol plus decylmethylsulphoxide, and accelerants which mainly modified the non-polar route e.g. propylene glycol plus oleic acid, propylene glycol alone and, to a limited extent, water.     

Simultaneous transport and metabolism of nicotinic acid derivatives in hairless mouse skin

In vitro simultaneous transport and metabolism of three ester prodrugs of nicotinic acid (NA), methyl nicotinate (MN), ethyl nicotinate (EN) and butyl nicotinate (BN) were studied using excised skin from hairless mouse. Hydrolysis studies of these esters with and without skin homogenate were also done at 37 degrees C. Both the ester and NA were detected in all receiver solutions in permeation studies, and no chemical hydrolysis of the esters was found, indicating that the esters were hydrolyzed during the skin permeation process. The total (ester+NA) flux from a saturated solution of ester prodrugs was higher than that of NA and was highest for MN, followed by EN and BN, whereas the total permeability coefficient of ester prodrugs increased from MN to BN. A difference in the NA/total flux ratio was found among these prodrugs; thus, esterase activity was also dependent on the alkyl chain length of the esters. The total flux from each ester solution increased linearly with the donor concentration. NA flux from MN and EN solutions increased with an increase in the donor concentration and reached a plateau at the high concentration range, suggesting that metabolic saturation occurred. NA fluxes at the plateau were similar among ester prodrugs and corresponded to the Vmax estimated from the hydrolysis experiment. The order of donor concentration at which NA reached a plateau also corresponded to the order of Km. It was confirmed that a difference in alkyl chain length of the ester prodrugs affected not only permeability but also metabolism in the skin permeation process.     

Transdermal delivery of glibenclamide and glipizide: in vitro permeation studies through mouse skin

The purpose of this investigation was to study the feasibility of transdermal delivery of glibenclamide and glipizide. In vitro permeation of these drugs was studied through mouse skin using various penetration enhancers like Tween -20, polyethyleneglycol-400, ethanol and d-limonene by simultaneous application of drug and enhancer solution or by pretreatment of the skin with neat enhancer. The partition coefficient values indicated that both drugs partition well into the skin. Glipizide did not show any skin metabolism, while glibenclamide showed a minimal metabolism during in vitro skin metabolism studies. The flux values (microgram/cm2/h) of both drugs significantly (p < 0.05) increased in the presence of penetration enhancers. The glibenclamide flux values ranged from 1.39 +/- 0.13 without enhancer, to 19.01 +/- 2.14 in a combination of 50% ethanol and 5% d-limonene. Glipizide flux values ranged from 3.01 +/- 0.74 without enhancer, to 62.97 +/- 7.10 in a combination of 50% ethanol and 5% d-limonene. Skin retention and solubility of both drugs increased with all penetration enhancers compared to control. The target permeation rates for glibenclamide and glipizide were calculated to be 193.8 and 184.8 micrograms/h respectively. The present study showed that the target permeation rates for both drugs could be achieved with the aid of enhancers by increasing the area of application in an appreciable range.     

Dodecyl N,N-Dimethylamino Acetate and Azone Enhance Drug Penetration Across Human,Snake, and Rabbit Skin

The effectiveness of the penetration enhancers, dodecyl N, N-dimethylamino acetate (DDAA) and Azone, on pretreated human epidermis for the permeation of model drugs, indomethacin, 5-fluorouracil, and propranolol-HCl, was studied in in vitro diffusion cells. Snakeskin (Elaphe obsoleta) and rabbit pinna skin were compared as possible models for human skin. The drug concentrations were analyzed by HPLC. With all skins and all model drugs, DDAA increased drug permeability at least as well as Azone, and in most cases it was a more effective permeation enhancer. The relative permeation improvements in human skin, snakeskin, and rabbit skin were 10- to 20-, 5- to 50-, and 20- to 120-fold, respectively. Tritiated water served as an indicator of skin condition. Its penetration in the skin samples was independent of the drugs used, and both penetration enhancers significantly increased the flux of tritiated water through all skins. Thus, DDAA and Azone significantly increased the permeation of lipophilic and hydrophilic model compounds. Rabbit pinna skin was a poor model for human skin in vitro, while snakeskin was much closer to human skin in terms of transdermal permeability. In most cases drug permeability decreased in the order rabbit human > or < snake.     

不同透皮促进剂对双氯芬酸钾凝胶体外透皮效果的影响研究

目的:考察氮酮(Azone)、丙二醇(PG)、油酸(OA)3种透皮促进剂一元、二元、三元联合对双氯芬酸钾凝胶的体外促透作用。方法:配制以下13种含不同透皮促进剂的双氯芬酸钾凝胶处方:空白,3%Azone,5%OA,12%PG,6%PG+2.5%OA,12%PG+5%OA,1.5%Azone+2.5%OA,1.5%Azone+6%PG+5%OA,1.5%Azone+12%PG,3%Azone+5%OA,3%Azone+6%PG,3%Azone+6%PG+5%OA,3%Azone+12%PG,以透皮速率J等为指标,采用改良的Franz扩散池,以离体人皮肤为透皮屏障,测定并计算双氯芬酸钾凝胶加入上述不同透皮促进剂处理后药物的透皮性能。结果:与空白组比较,其它各组J值均升高,其中以3%Azone+12%PG组的J值最高,达10.253 0μg.cm-2.h-1。结论:3种透皮促进剂对双氯芬酸钾凝胶均有不同程度促透效果,但以Azone和PG二元联用效果最佳。     

Structure-activity relationship of 1-alkyl- or 1-alkenylazacycloalkanone derivatives as percutaneous penetration enhancers

Nine azacycloalkanone (5-, 6-, or 7-member ring) derivatives with an alkyl or alkenyl (terpene) chain (10, 15, or 20 carbons) were compared with 1-dodecylazacycloheptan-2-one (azone, 1) for their effects on the percutaneous penetration of 6-mercaptopurine (6-MP) through excised guinea pig skin. Pretreatment of skin with an enhancer markedly increased penetration and skin accumulation of 6-MP. Superior enhancing effects were observed for enhancers having a terpene chain of 10 carbons and an azacyclo ring with one carbonyl group. Enhancers with a C20 tail chain were less effective. Enhancer ring size had little effect on enhancing activity, whereas the increase in the number of carbonyl groups in the ring caused a decrease. Computer fitting of a penetration profile to Fick's diffusion equation gave two parameters corresponding to diffusion and partitioning of 6-MP. The diffusion parameter was little affected by pretreatment with an enhancer, whereas the partition parameter was markedly increased. This suggests that enhancement is determined by the ability to increase the drug partitioning into the skin and to enlarge the drug concentration gradient in the skin barrier. The primary skin irritation was examined with rabbit dorsal skin in vivo. The enhancers with an alkyl chain induced severer primary irritation (erythema and edema) than those with an alkenyl chain. From the balance between enhancing and irritating activities, it is concluded that 1-geranylazacycloheptan-2-one, 1-farnesylazacycloheptan-2-one and 1-farnesylazacyclopentan-2-one are favorable enhancers.     

几种增渗剂对吡喹酮经离体鼠皮渗透性的影响

本文利用水平式Ｖａｌｉａ－Ｃｈｉｅｎ扩散池考察了过饱和生理盐水溶液中药物经离体鼠皮的渗透性及不同增渗剂的促渗作用，同时考察了吡喹酮体外经活性表皮的渗透性，结果表明吡喹酮经离体鼠皮及其活性表皮的渗透系数分别为４．７３×１０~（－６）ｃｍ／ｓ和２．９２５×１０~（－５）ｃｍ／ｓ，稳态流量分别为１．３１３×１０~（－３）μｇ／ｃｍ~２．ｓ和８．１１１×１０~（－３）μｇ／ｃｍ~２·ｓ，滞后时间分别为１．５２５ｈ和０．８６４ｈ，对皮肤经增渗剂处理前后，吡喹酮体外经皮的渗透实验结果表明月桂氮酮、泊洛沙姆１８８和油酸对其经皮渗透均有一定的促进作用，其中３％月桂氮酮的促渗作用最为显著，而Ｎ－乙基－２－吡咯烷酮则无明显增渗作用。此外，测定了吡喹酮在正辛醇／水、全皮／水和角质层／水的分配系数，结果表明药物的亲脂性极强。     

Enhanced penetration of mitomycin C through hairless mouse and rat skin by enhancers with terpene moieties

The effects of four new percutaneous absorption enhancers containing an azacyclo ring and terpene chain (1-geranylazacycloheptan-2-one (GAH), 1-farnesylazacycloheptan-2-one (FAH), 1-geranylazacyclopentan-2,5-dione (GAPD), and 1-farnesylazacyclopentan-2-one (FAP] and 1-dodecylazacycloheptan-2-one (Azone) on the percutaneous penetration of mitomycin C (MMC) through hairless mouse and rat skin in-vitro has been investigated. GAH, FAH, FAP and Azone enhanced MMC penetration by 20 to 60 times that of the control (ethanol). During the early part of the experiments, when the sink condition was maintained, FAH was the most effective for hairless mouse skin, whereas Azone showed the highest effect in the rat skin. The enhancing effect of GAPD was only about half that of the other enhancers, suggesting the importance of the polar group of the ring moiety in these compounds. The penetration of MMC through rat skin was also increased by pretreatment with these compounds, suggesting that the enhancers had a direct effect on the skin.     

Novel approach to improve permeation of ondansetron across shed snake skin as a model membrane.

The purpose of this study was to investigate the feasibility of transdermal drug delivery of ondansetron, an antagonist of the 5-HT3 receptor, used for the treatment of chemotherapy-induced emesis. The permeability of ondansetron from an aqueous suspension through shed snake skin as a model membrane was very low and in order to improve it, several enhancers were tested. Ethanol increased the flux at a concentration of 40% or more. The solubility of ondansetron also increased as the ethanol concentration increased. The permeability coefficient increased after pretreatment of the shed snake skin with Azone, oleic acid or lauryl alcohol. Further improvement of the permeability was observed when ethanol was combined with other enhancers and was maximum for the combination of ethanol and oleic acid. Oleic acid dramatically increased the partition of ondansetron to n-hexane and shed snake skin. Oleic acid may enhance the permeation of ondansetron in two ways: by a direct effect on the stratum corneum or via counterion formation of an ion-pair. The maximum flux obtained from the combination of ethanol and other enhancers seems to be high enough to obtain a therapeutic effect.     

透皮促进剂对白花前胡甲素体外经皮渗透的影响

目的:考察透皮促进剂对白花前胡甲素(dl-praeruptorin A,Pd-Ia)体外经皮渗透的影响。方法:采用改进的Franz扩散池,以大鼠离体皮肤为渗透屏障,用高效液相色谱法对Pd-Ia进行含量测定,考察月桂氮酮(Azone)及1%Azone与不同浓度丙二醇(PG)混合物对Pd-Ia透皮吸收的影响。结果:使用Azone对Pd-Ia有促透作用,1%Azone效果较好,平均渗透速率达到4.064μg.cm-2.h-1;1%Azone与15%PG合用促透效果最好,平均渗透速率达到4.889μg.cm-2.h-1,且与单用1%Azone有显著性差异(P<0.05)。结论:1%Azone与15%PG合用时,含0.5%Pd-Ia溶液体外渗透具有最大促透效果,体现出协同作用。     

Synthesis and Enhancing Effect of Dodecyl 2-(N,N-Dimethylamino)propionate on the Transepidermal Delivery of Indomethacin,Clonidine, and Hydrocortisone

The biodegradable transdermal penetration enhancer, dodecyl 2-(N,N-dimethylamino)propionate (II; DDAIP), was prepared by reacting dodecyl 2-bromopropionate (I), obtained by reaction of n-dodecanol with 2-bromopropionyl halogenide, with dimethylamine. The penetration enhancing effects of DDAIP on the transport of indomethacin, clonidine, and hydrocortisone across shed snake skin (Elaphe obsoleta) were evaluated. Azone and lauryl alcohol, a possible decomposition product of DDAIP, were used as standard enhancers for comparison. In terms of flux, DDAIP showed 4.7 and 7.5 times the promoting effect for indomethacin compared to azone and lauryl alcohol, respectively. With clonidine this effect was 1.7 and 3.1 times, whereas with hydrocortisone it was 2.4 and 2.8 times higher, respectively. In vitro biodegradability of DDAIP was demonstrated in the presence of porcine esterase. The results indicate that DDAIP increases markedly the transepidermal delivery of several types of drug substances.     

Evaluation of in vitro percutaneous absorption of lorazepam and clonazepam from hydro-alcoholic gel formulations

Clonazepam and lorazepam are two anxiolytics, antidepressant agents, having suitable features for transdermal delivery. The objectives of this study were to evaluate the in vitro percutaneous absorption of these drugs through excised human skin (stratum corneum and epidermis, SCE) and to determine their in vitro permeation behavior from a series of hydro-alcoholic gel formulations containing various enhancing agents. The best permeation profile was obtained for both drugs applying them together with Azone in combination with propylene glycol (PG): these enhancers were able to increase the clonazepam and lorazepam percutaneous fluxes at steady-state about threefold, compared to the free enhancer formulations (Control). To explain the mechanism of the used promoters, the benzodiazepine diffusion and partitioning coefficients from the gel containing the enhancers were calculated. The results indicated that the Azone in combination with PG could act by increasing the benzodiazepine diffusion coefficients, Transcutol increased only the SC/vehicle partition coefficients, limonene in combination with PG appeared to increase both partition and diffusion coefficients moderately, while PG did not increase both the parameters. Furthermore, to evaluate the potential application of tested benzodiazepine formulations containing Azone in combination with PG using the flux values from the in vitro experiments, the corresponding steady-state plasma concentrations (C(SS)) were calculated. The obtained calculated C(SS) values are within the lorazepam therapeutic range and suggest that transdermal delivery of this drug could be regarded as feasible.     

促渗剂Azone对几种药物透皮速率的影响

Azone(氮酮)是目前国内外所应用的最好的药物透皮吸收促渗剂之一。本文用~3H-Azone作示踪剂,以离体皮肤体外流通扩散室法,研究了国产Azone对α-细辛醚、硝烟酯和硝酸甘油贴剂中药物渗透速率的影响。实验结果表明,Azone能显著增加上述三种药物的渗透速率,在Azone含量为4.8％时,硝烟酯、硝酸甘油和α-细辛醚的渗透速率分别增加133.7％、82.1％和34.5％,而且增渗作用持久。     

Transdermal delivery of indomethacin and levonorgestrel using clofibric acid amides as penetration enhancers

The enhancing properties of clofibric acid amides on the transdermal delivery of indomethacin and levonorgestrel were studied in vitro using full-thickness hairless mouse skin. The enhancers possessed alkyl side chains varying from 2 (1) to 16 (7) carbons. Indomethacin was applied in propylene glycol and levonorgestrel in 1-butanol, and all enhancers were applied at 0.4 M in propylene glycol 1 h prior to drug treatment. 1-Butanol was chosen as the vehicle for levonorgestrel since it was found to deliver more drug transdermally than propylene glycol. Since this was a volatile solvent, all experiments with levonorgestrel were performed under occlusion. The greatest increases in permeability coefficients and skin retention of model drugs were observed with compounds 4, 5, and 6. The permeability coefficient enhancement ratio (ER) for indomethacin and 4 was 3.1, for 5 was 10.9, and for 6 was 14.6. Skin content ER values were 4.6, 5.3, and 1.8, respectively. Levonorgestrel permeability coefficient ER values were lower, 1.6 for 4, 2.6 for 5, and 1.9 for 6. Skin content ER values for this model drug were 1.7, 4.3, and 2.3, respectively. Azone, however, was less effective than 5 and 6 for both model drugs with respect to permeability coefficients and 24-h receptor concentrations. For skin contents and indomethacin, 2-7 were more effective than Azone, and for levonorgestrel, 5, 6, and 7. Indomethacin enhancement was dependent on concentration of enhancer 6 (0.1, 0.2, 0.4, 0.6, 0.8 M), the maximum being observed for 0.4, 0.6, and 0.8 M. Permeation enhancement of both drugs was dependent on the length of the alkyl side chain of the enhancer. It is proposed that these compounds may be useful for transdermal drug delivery, although further testing needs to be performed.     

Influences of alkyl group chain length and polar head group on chemical skin permeation enhancement

Previous investigations in our laboratory on the influence of the n-alkanols and the 1-alkyl-2-pyrrolidones as skin permeation enhancers for steroid molecules as permeants demonstrated that the enhancer potencies (based on aqueous concentration values) of these two homologous series were the same when compared at the same alkyl chain length; that is, the contribution of the hydroxyl group and that of the pyrrolidone group to enhancer potency were the same. The purpose of the present study was to further investigate what was believed to be a somewhat surprising finding, and two additional homologous series, the 1,2-alkanediols and N,N-dimethylalkanamides, were selected for study as enhancers. Corticosterone (CS) flux enhancement along the lipoidal pathway of hairless mouse skin stratum corneum was determined with 1,2-hexane-, 1,2-octane-, and 1,2-decanediol and with N,N-dimethylhexanamide, N,N- dimethylheptanamide, N,N-dimethyloctanamide, and N,N-dimethylnonanamide as enhancers. The enhancement factor (E) for the lipoidal pathway was calculated from the CS permeability coefficient and the CS solubility data over a 4 to 100 range of E values. Comparisons of the enhancer potencies of all four homologous series revealed that the enhancer potencies of all were very nearly the same when compared at equal alkyl group chain length. Moreover, the contribution of each of the polar head groups toward the enhancer potency was essentially constant, independent of the alkyl group chain length. It was reasoned that this outcome was either the result of the random selection of four polar head groups making the same contribution to enhancer potency or the result of these particular polar head groups not contributing to enhancer potency. To test the hypothesis that the former was more likely than the latter and that a suitable semipolar organic phase may mimic the microenvironment of the polar head group at the site of enhancer action, n-octanol-phosphate buffered saline (PBS) and n-hexane-PBS partition coefficients were determined for all the enhancers. The n-octanol-PBS partition coefficients for the enhancers, but not the n-hexane-PBS partition coefficients, were very nearly the same when compared at equal alkyl group chain lengths; this result supports the hypothesis that each of the four polar head groups likely contributes the same toward the enhancer potency and locates in the semipolar region of the hairless mouse skin stratum corneum lipid bilayers, which is well-approximated by water-saturated n-octanol.     

The effects of several penetration-enhancers on the simultaneous transport and metabolism of ethyl nicotinate in hairless rat skin

The effects of enhancers such as Azone, L-menthol, ethanol and the l-menthol-ethanol-water (MEW) system on the simultaneous transport and metabolism of ethyl nicotinate (EN) through excised hairless rat skin were measured. The sum of the skin permeability coefficients of EN and its metabolite, nicotinic acid (NA), was utilized to assess their penetration-enhancement abilities, and the flux ratio of NA against the total (EN + NA) flux was used as a metabolic index to evaluate the effect of the enhancers on the skin metabolism of EN. The addition of 1% l-menthol increased the total skin permeability coefficient to about 2.5 times that of the control (without l-menthol), whereas 40% ethanol decreased this coefficient. This was probably due to the lowered thermodynamic activity of EN in the vehicle caused by the addition of ethanol. The simultaneous use of l-menthol and ethanol (MEW system) showed a similar permeability coefficient to that of the control. This may be explained by the decreased activity of EN caused by ethanol and by the increased diffusivity of the skin caused by l-menthol. All of the enhancers decreased the metabolic index in hairless rat skin, compared to the control. The reversibility of this index was then evaluated with a pretreatment experiment of the enhancers. The metabolic activity from EN to NA in skin was immediately recovered after the removal of ethanol, l-menthol or MEW system. The penetration-enhancing effect resulting from 1% l-menthol pretreatment was lower than that resulting from MEW pretreatment or 3% Azone pretreatment. With respect to the metabolic index recovery rate in skin, l-menthol may be much safer than Azone. l-Menthol, ethanol and the MEW system are therefore safe and effective ways to enhance or control skin permeation and to decrease the skin metabolism of prodrugs and peptides which are easily bioconverted in skin.     

Synergistic effects of ethosomes and chemical enhancers on enhancement of naloxone permeation through human skin

The purpose of this study was to investigate the effects of ethosomes, chemical enhancers and their binary combination on the in vitro permeability enhancement of naloxone through human skin. Franz diffusion cells were used for the percutaneous absorption studies. Propylene glycol (PG), N,N-dimethyl formamide (N,N-DMF), N,N-dimethyl acetamide (N,N-DMA), dimethyl sulfoxide (DMSO), Azone and polyethylene glycol 400 (PEG400), were chosen as the chemical enhancers. Naloxone ethosomes showed 11.68 times increase in steady-state flux compared to phosphate buffered solution (PBS). Ethosomes in combination with chemical enhancers synergistically increased (p < 0.05) in vitro flux of naloxone. Azone 3% + PG7% pretreated in ethosomal form dramatically enhanced the skin permeation of naloxone in vitro compared with ethosomes (steady-state flux: 96.75 +/- 5.70 microg x cm(-2) x h(-1) vs 20.56 +/- 1.67 microg x cm(-2) x h(-1)). Ethosomal carrier and enhancers accumulated in the skin after 24 h were greater than that of PBS.     

Factors influencing hydrocortisone permeation into human hair follicles: use of the skin sandwich system

The aim of the present study was to use the in vitro human skin sandwich system in order to quantify the influence of formulation variables on intrafollicular hydrocortisone permeation. The investigated variables were the pH and the viscosity of the topical formulation as well as the presence of chemical enhancers (carvone, menthone, oleic acid and sodium lauryl sulphate). Furthermore, skin sandwich hydration was also varied in order to determine if the method itself can be run using only partially hydrated skin tissues. It was determined that the follicular contribution to hydrocortisone flux decreased marginally with increasing alkalinity in the pH range 3-8.8. Intrafollicular penetration was markedly reduced when HPMC gels were used instead of an aqueous solution. Pretreating the skin with chemical enhancers also reduced the follicular contribution to flux, probably due to permeabilisation of the continuous stratum corneum. Furthermore, it was not possible to satisfactorily modify the skin sandwich method so that it could be deployed using less hydrated skin.     

Use of an 8(1)3(2) asymmetrical factorial design for the in vitro evaluation of ondansetron permeation through human epidermis

The in vitro permeation of ondansetron through human cadaver epidermis, as a preliminary step toward the development of a transdermal therapeutic system, was investigated. In vitro release studies were carried out using modified Franz diffusion cells and human epidermis, taken from cadaver skin by heat separation technique. To estimate the effect of the type and concentration of the penetration enhancers and the skin from different donors, an 8(1)3(2) asymmetrical factorial design was used. Formulations containing lauric acid and oleic acid as penetration enhancers, showed the largest Q values [amounts of ondansetron permeated per unit area of epidermal membrane (microg/cm2)] at 24, 48, and 72 hr, as well as steady-state flux values, among all formulations tested. The other enhancers increased the flux in the following order: lauryl alcohol>glycerol monooleate>Azone >cineole>oleyl alcohol>1-methyl-2-pyrrolidinone. Moreover, the concentration of the penetration enhancer and the type of the skin were proved to significantly affect the permeation rate of ondansetron through human epidermis. From the results obtained, it was shown that the formulations containing lauric acid or oleic acid at 5% or 10% could increase sufficiently the permeation of ondansetron. Therefore, the transdermal administration of ondansetron seems feasible.