In vitro percutaneous absorption of metal compounds

It is well known that contact with metals can be responsible for allergic contact dermatitis; also, there is experimental evidence that nickel ions are readily available on the surface of used coins containing nickel and copper. The aim of this study was to prove that metal powders of nickel (Ni), cobalt (Co) and chromium (Cr) dispersed in synthetic sweat are oxidised into respective ions that can permeate the skin. Suspensions of 5 g of metal powder (Ni, Co and Cr) in 100 mL of synthetic sweat at pH 6.5 were prepared and shaken with a stirring plate at room temperature for 30 min. Human skin membranes were set up in Franz-diffusion cells and 2 mL of the freshly made suspension were applied to the outer surface of the skin for 24h. The appearance of metal ions in the aqueous receptor phase (NaCl 0.9%) was quantified by Electro Thermal Atomic Absorption Spectroscopy (ETAAS). Also, metals ions were analysed using Differential Pulse Polarography (DDP), Differential Pulse Voltammetry (DPV) and Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) techniques both in the receiving phase and in the donor solution to evaluate the presence of different ionic metallic species. DPP and DPV measurements of cobalt and nickel suspensions confirmed the presence of Co2+ and Ni2+ ions in concentration, respectively of 33.3+/-3.2 and 27.1+/-3.2 mg L(-1). Chromium ions concentration below 0.1 mg L(-1) were found in chromium suspensions bearing evidence of synthetic sweat inefficacy of oxidising chromium metal powder. Cobalt and nickel skin permeation was demonstrated in in vitro experiments using the Franz cell system giving a permeation flux of 0.0123+/-0.0054 microg cm(-2) h(-1) for cobalt and of 0.0165+/-0.00036 microg cm(-2) h(-1) for nickel and a lag time of 1.55+/-0.71 h for cobalt and of 14.56+/-0.56 for nickel. Chromium below 0.1 microg L(-1) was found in the receiving solutions. Our experiments demonstrated that metallic nickel and cobalt can be oxidised when suspended in synthetic sweat, while chromium would probably need stronger oxidising conditions. Metallic ions can permeate the skin and the Franz cell system showed that it is possible to measure a flux of ions through the skin for cobalt and nickel but not for chromium.     

盐酸布替萘芬乳膏的离体透皮吸收研究

目的:研究盐酸布替萘芬乳膏对离体豚鼠皮的透皮吸收情况,并对自制乳膏与国内外已上市产品的离体透皮渗透量进行比较。方法:采用透皮吸收仪,皮片涂药后不同时间采样,用高效液相色谱法测定样品中盐酸布替萘芬的浓度。结果:在50%乙醇生理盐水释放液中,国外产品、国内产品和自制产品36 h透皮渗透量分别只有0.061 89,4.661,和0.289 7μg.cm-2,盐酸布替萘芬乳膏透皮渗透量很低,三者无显著性差异。结论:自制盐酸布替萘芬乳膏的豚鼠离体透皮吸收程度与国外同类品种相当。盐酸布替萘芬乳膏主成分大部分滞留在皮肤,只有极少数透过皮肤屏障,有利于其发挥局部治疗作用。     

In vitro percutaneous absorption of captopril through excised rabbit skin

The permeation characteristics of captopril through excised rabbit skin at various pH values of McIlvaine buffer solutions were investigated. These results indicated that the pH dependency in skin permeability of zwitterionic drug may reflect the permselective property of the skin dependent on the lipophilicity and/or diffusivity of the ionic species. The surfactants were used as penetration enhancers to increase the percutaneous absorption of captopril. These surfactants all showed significant increase (ANOVA, P < 0.05) in the enhancing effect compared with that of the control group. Among the surfactants, sodium lauryl sulfate showed the greastest effect on the penetration which increased the flux approximately 58.8-fold and the enhancement increased following the increase of surfactant concentration.     

In vitro and in vivo percutaneous absorption of catechol.

The Cosmetic Ingredient Review Expert Panel found insufficient data to conclude that catechol could be used safely in permanent hair dye products. Information was lacking on the extent of oxidation and skin absorption of remaining catechol. In vitro percutaneous absorption studies were conducted in human and rat skin using a consumer permanent hair dye spiked with 0.6% catechol. A 30-min application demonstrated 0.4% of the applied dose was absorbed through human skin and 0.2% through rat skin. The minimal absorption observed was due to the short exposure time and to partial oxidation of catechol by the dye developer. The fate of catechol remaining in rat skin after exposure in vitro and in vivo was investigated with additional absorption studies using catechol in ethanol. At 72 h, 24-h application of 4% catechol resulted in skin absorption of 81% of the applied dose in vitro and 53% in vivo. Skin levels measured at 24 h remained unchanged after 72 h. Therefore the skin reservoir did not contribute to the estimated systemic absorption. A deconvolution technique employed to predict skin absorption using plasma levels from intravenous and dermal administration overestimated in vivo skin absorption due to volatility of catechol in an ethanolic vehicle.     

In vitro hydrolysis of steroid acid ester derivatives of prednisolone in plasma of different species

The in vitro hydrolysis of two new classes of steroid acid esters synthesized from prednisolone as local anti-inflammatory steroids was investigated in rat, rabbit, and human plasma. One class was synthesized by incorporating methoxycarbonyl groups at the 16 position of prednisolone to produce 16 alpha-methoxycarbonyl prednisolone (P16CM) and its 17-deoxy analogue (DP16CM). The other class was synthesized by modifying the ketol side chain of prednisolone to produce methyl 20 alpha- and methyl beta-dihydroprednisolonate (P4 alpha and P4 beta). The P16CM and P4 beta were rapidly and completely hydrolyzed within 1 h of incubation in rat and rabbit plasma and within 4 h in human plasma. There was a marked species difference in the hydrolysis of DP16CM which occurred in the following order: rat greater than human greater than rabbit. The in vitro hydrolysis of P4 alpha was much slower than that of P4 beta; the process continued over 24 h in rat plasma. As expected, no change in the initial concentration of prednisolone was found over 120 h of incubation in rat plasma. This marked species difference in the hydrolysis of these steroid acid esters is probably related to the differences in the amounts, types, and activities of the hydrolyzing enzymes (e.g., esterases) in the plasma of the three species. From this study it can be concluded that the existence of an hydroxyl group at C-17 and the orientation of hydroxyl groups at C-20 play an important role in the systemic hydrolysis rate of the carboxy ester group on the steroid nucleus.     

In vitro percutaneous absorption in mouse skin: influence of skin appendages

Skin appendages are often envisaged as channels that bypass the stratum corneum barrier and are generally thought to facilitate the dermal absorption of topical agents. However, the significance of this transappendageal pathway in percutaneous absorption remains to be assessed experimentally. With the use of a skin organ culture penetration chamber system, the influence of skin appendages on the in vitro permeation of topically applied benzo[a]pyrene and testosterone (5 micrograms/2 cm2) was examined in skin preparations from both haired and hairless mice. Haired mice examined included the C57BL6, C3H, DBA2, Balbc, and Sencar strains and the hairless mice were the HRS and SKH. In all mouse strains examined, the overall permeation of testosterone (greater than 65% of applied dose) 16 hr following in vitro topical application was greater than that of benzo[a]pyrene (less than 10%). No strain differences were observed with respect to the percutaneous permeation of testosterone; however, percutaneous permeation of benzo[a]pyrene in the haired mice (7-10% of applied dose) was higher than that in the hairless mice (2%). In an in-house derived mouse strain which showed three phenotypic variants due to hair densities, the permeability to both compounds was highest in the skin of the haired phenotype (testosterone 67%, benzo[a]pyrene 7%), lowest in the hairless phenotype (35 and 1%, respectively) and intermediate in the fuzzy-haired animal (57 and 3%, respectively). Examination by fluorescence microscopy of cryosections of skin, prepared 1 hr after topical benzo[a]pyrene, showed areas of intense fluorescence deep within the nonfluorescing dermis of skin from the haired phenotype. These fluorescent areas were correlated with follicular ducts and sebaceous glands. In contrast, skin from the hairless phenotype showed no evidence of fluorescence in the dermis and intermediate was the fluorescence observed in the skin from the fuzzy-haired animal. These observations showed that transappendageal penetration could contribute significantly to the overall skin absorption of topical agents. They also suggest that regional distribution of skin appendages could influence the percutaneous fate of topically applied chemicals.     

In vitro percutaneous absorption of chromium powder and the effect of skin cleanser

The present study tried to investigate, using a synthetic sweat at pH 4.5, whether metallic chromium can pass through the skin (in vitro) and the effect of rapid skin decontamination with a common detergent. A suspension of chromium powder in synthetic sweat at pH 4.5 was prepared and shaken with a stirring plate at room temperature for 30min. Human skin membranes were set up in Franz-diffusion cells and 1ml of the freshly made suspension was applied to the outer surface of the skin for 24h. The tests were performed without and with decontamination using the cleanser 30min after the start of exposure. The appearance of metal ions in the aqueous receptor phase was quantified by Electro Thermal Atomic Absorption Spectroscopy (ETAAS) and Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES). Speciation analysis and measurements of chromium skin content were also performed. Chromium skin permeation was demonstrated in in vitro experiments using the Franz cell system, giving a permeation flux of 0.84+/-0.25ngcm(-2)h(-1) and a lag time of 1.1+/-0.7h. The cleaning procedure stop Cr permeation but its concentration into the skin significantly increased (Mann-Witney U test P<0.03). The results revealed that chromium applied as powder can pass through the skin and that decontamination, done after 30min of exposure, prevent Cr skin permeation but increase Cr content into the skin.     

In vitro percutaneous absorption of piroxicam through synthetic membranes and abdominal rat skin

The in vitro release of piroxicam from carbomer gels and its penetration through isopropyl myristate impregnated membranes and abdominal rat skin were investigated. Attempts were made to relate the differences in the release rate with physicochemical properties of the drug and the vehicle. The results showed that piroxicam is released from the topical gel formulations and diffuses through skin. It is suggested that although piroxicam flux across abdominal rat skin was lower than through isopropyl myristate membranes, this kind of membranes can be used in preliminary screening among the different piroxicam formulations.     

烫伤膜体外透皮吸收的实验研究

目的:考察烫伤膜的体外透皮吸收效果.方法:采用半透膜作为渗透屏障,研究烫伤膜及烫伤油的皮肤渗透作用.结果:烫伤膜可透过半透膜,释药动力学方程:Q=-2.4895 t2 89.372t,r=0.9108.烫伤油24h未能测出大黄素含量.结论:烫伤膜中大黄素具有较好的透皮效果.     

In vitro solubility assays in drug discovery

The solubility of a compound depends on its structure and solution conditions. Structure determines the lipophilicity, hydrogen bonding, molecular volume, crystal energy and ionizability, which determine solubility. Solution conditions are affected by pH, co-solvents, additives, ionic strength, time and temperature. Many drug discovery experiments are conducted under "kinetic" solubility conditions. In drug discovery, solubility has a major impact on bioassays, formulation for in vivo dosing, and intestinal absorption. A good goal for the solubility of drug discovery compounds is >60 ug/mL. Equilibrium solubility assays can be conducted in moderate throughput, by incubating excess solid with buffer and agitating for several days, prior to filtration and HPLC quantitation. Kinetic solubility assays are performed in high throughput with shorter incubation times and high throughput analyses using plate readers. The most frequently used of these are the nephelometric assay and direct UV assay, which begin by adding a small volume of DMSO stock solution of each test compound to buffer. In nephelometry, this solution is serially diluted across a microtitre plate and undissolved particles are detected via light scattering. In direct UV, undissolved particles are separated by filtration, after which the dissolved material is quantitated using UV absorption. Equilibrium solubility is useful for preformulation. Kinetic solubility is useful for rapid compound assessment, guiding optimization via structure modification, and diagnosing bioassays. It is often useful to customize solubility experiments using conditions that answer specific research questions of drug discovery teams, such as compound selection and vehicle development for pharmacology and PK studies.     

In vitro and in vivo percutaneous absorption of topical dosage forms: case studies

This article evaluated the influence of vehicle compositions on topical drug availability. In vitro drug release and in vivo experiments were performed in case of the hydrophilic ketamine hydrochloride and the lipophilic piroxicam. Ketamine hydrochloride is a NMDA receptor antagonist that has been useful for anesthesia and analgesia. The study of transdermal ketamine delivery is a novelty, because nobody has investigated the hypnotic effects of ketamine after this administration route. In vitro measurements gave a good basis for screening among the developed products. The physiological changes after ketamine administration showed, that there were significant differences among the parameters tested (breathing rate, duration of sleep) from the developed products (hydrogel, lyotropic liquid crystal and o/w cream) compared to the reference product (Carbopol gel). The in vivo feedback for piroxicam was the measurement of the anti-inflammatory activity by edema inhibition percentage. Significant differences were measured in case of the developed systems compared to the reference.     

Influence of modified cyclodextrins on solubility and percutaneous absorption of celecoxib through human skin

We evaluated the ability of two modified cyclodextrins, hydroxypropyl-beta-cyclodextrin (HP-beta-Cyd) and 2,6-di-O-methyl-beta-cyclodextrin (DM-beta-Cyd), to influence the percutaneous absorption through isolated human stratum corneum and epidermis (SCE) of celecoxib (CCB). Previous studies demonstrated that DM-beta-Cyd includes the drug, producing a significant increase of water solubility (0.5 mg/ml at 25 degrees C) and dissolution rate of CCB. In this work chemical-physical characterization studies were performed to evaluate the ability of HP-beta-Cyd to include CCB. We showed that only an external interaction could exist between CCB and HP-beta-Cyd that positively influences the water solubility of the drug (0.12 mg/ml at 25 degrees C for CCB-HP-beta-CyD system and 4.12 x 10(-3) mg/ml at 25 degrees C for free CCB). In vitro percutaneous experiments were performed using samples in solution and in suspension containing different Cyd concentrations. Both HP-beta-Cyd and DM-beta-Cyd enhanced drug flux through SCE by means of an increase of dissolution rate of the drug as well as a direct action on the stratum corneum (SC). Histological analysis of treated SCE showed a protective effect of the two Cyds towards an invasive action shown by CCB on SC.     

Percutaneous absorption of ketoprofen. I. In vitro release and percutaneous absorption of ketoprofen from different ointment bases

Ketoprofen (KP) is a potent non-steroidal anti-inflammatory drug which is used for the treatment of rheumatoid arthritis. The oral administration of KP can cause gastric irritation and renal adverse effects. Topical application of the drug can bypass gastrointestinal disturbances and provide relatively consistent drug levels at the site of action. Since the efficacy of an ointment depends on the type of ointment base and the concentration of the drug, four different bases (white petrolatum, cold cream, hydrophilic ointment and Carbopol 940 gel) were used at 1, 3, 5, 7 and 10% concentrations of KP to evaluate the effect of ointment base and concentration. The general rank order of the drug release was found to be: Carbopol gel > hydrophilic ointment > cold cream > white petrolatum. There was a positive correlation between the concentration of KP and release rate for all bases except Carbopol gel. The in vivo percutaneous absorption of KP from different ointment bases at 3% concentration was studied by carrageenan-induced paw edema in mice. The rank order of the percent edema inhibition was as follows: Carbopol gel ≥ hydrophilic ointment > cold cream > white petrolatum. There was a good correlation between the in vitro and in vivo results.     

Metabolism of captopril carboxyl ester derivatives for percutaneous absorption

Objectives To determine the metabolism of captopril n‐carboxyl derivatives and how this may impact on their use as transdermal prodrugs. The pharmacological activity of the ester derivatives was also characterised in order to compare the angiotensin converting enzyme inhibitory potency of the derivatives compared with the parent drug, captopril. Methods The metabolism rates of the ester derivatives were determined in vitro (using porcine liver esterase and porcine ear skin) and in silico (using molecular modelling to investigate the potential to predict metabolism). Key findings Relatively slow pseudo first‐order metabolism of the prodrugs was observed, with the ethyl ester displaying the highest rate of metabolism. A strong relationship was established between in‐vitro methods, while in‐silico methods support the use of in‐vitro methods and highlight the potential of in‐silico techniques to predict metabolism. All the prodrugs behaved as angiotensin converting enzyme inhibitors, with the methyl ester displaying optimum inhibition. Conclusions In‐vitro porcine liver esterase metabolism rates inform in‐vitro skin rates well, and in‐silico interaction energies relate well to both. Thus, in‐silico methods may be developed that include interaction energies to predict metabolism rates.     

基于全自动二维液相色谱的地奈德乳膏体外经皮渗透研究

目的建立乳膏及经皮渗透样品中地奈德的全自动二维液相色谱(2D-LC-UV)测定法,比较新研制的地奈德乳膏与原研制剂的体外经皮渗透性。方法采用ASTON RG C30色谱柱(4.6 mm×150 mm,5μm),流动相为四氢呋喃-水-乙腈=25:35:40,流速为1.0 m L·min~(-1),检测波长245 nm。体外透皮实验采用改良Franz扩散池,以离体乳猪皮为屏障,以累积渗透量和皮肤滞留量为指标,评价新研制的地奈德乳膏与原研制剂的经皮渗透规律。结果皮肤接收液和皮肤提取液样品中地奈德浓度分别在10~1000ng·m L~(-1)、10~300 ng·m L~(-1)内线性关系良好(r~2=0.999,r~2=0.997)。与原研制剂相比,新研制的地奈德乳膏在2、7、12、24 h的单位皮肤面积累积渗透量和2、24 h皮肤滞留量差异均无统计学意义(P>0.05)。结论所建立的2D-LC-UV方法快速、准确,可用于地奈德乳膏的含量测定及体外经皮渗透规律研究。新研制的地奈德乳膏的经皮渗透特性与原研制剂相似。     

In vitro dermal absorption of carfentanil

There is growing concern regarding potential occupational exposures to the ultra-potent synthetic opioid carfentanil. However, little data are available on the toxicity of carfentanil in humans, particularly for dermal exposures. To begin to address this, permeation of carfentanil formulated in three vehicles, water, ethanol, and hand sanitizer was measured under infinite-dose conditions in an in vitro static diffusion cell system using the EpiDerm™ (EPI-606-X) RhE model. The permeation rate was fastest for carfentanil in water (3.9 × 10⁻³ cm/h), followed by hand sanitizer (1.2 × 10⁻³ cm/h), and slowest for carfentanil in ethanol (0.2 × 10⁻³ cm/h). In both ethanol and hand sanitizer, a lag-time between exposure and permeation of approximately 1.5 h was observed, while lag-time in water was approximately half an hour. Flux at steady-state was greater at 50.6 μg/ml than at 5.3 μg/ml for both water and ethanol; however, the percent of dose absorbed did not differ between doses for either vehicle. Slight differences in percutaneous permeation of carfentanil were observed between two brands of hand sanitizer, likely due to differences in relative proportion of alcohol and skin penetration enhancers. These data indicate that small skin exposures may not result in rapid, significant toxicity as previously reported.