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PubMed1982

Skin absorption of aniline from aqueous solutions in man.

The skin absorption of aniline, aniline with 3% water content, and 1 and 2% aqueous aniline solutions was investigated in man. The time of exposure was 30 or 60 min. The absorbed amount of aniline was calculated on the basis of rho-aminophenol excretion in 24-h urine. The rate of aniline absorption from aqueous solutions was approx. 0.20 to 1.22 mg/cm2/h. There was no significant difference between the mean rate of absorption of liquid aniline (3.0 mg/cm2/h) and that with 3% content of water (2.5 mg/cm2/h).

Adult↗
PubMedDate not supplied

In vitro skin absorption and decontamination of sulphur mustard: comparison of human and pig-ear skin.

The aim of this study was to evaluate the use of an in vitro skin diffusion cell system as a model for assessing decontaminants against the chemical warfare agent sulphur mustard (SM). The in vitro absorption rates of SM through heat-separated human (157 +/- 66 microg cm(-2) h(-1)) and pig-ear (411 +/- 175 microg cm(-2) h(-1)) epidermal membranes were in agreement with previous in vivo studies that quoted skin absorption rates of 150 and 366 microg cm(-2) h(-1), respectively. Decontaminants (fuller's earth, Ambergard and BDH spillage granules) were ranked in order of effectiveness by measuring the skin absorption rates and the percentage of applied dose of SM that penetrated human and pig-ear epidermal membranes. The effectiveness of fuller's earth measured in this in vitro study using human epidermal membranes was in agreement with a previous in vivo human volunteer study. Similarly, the effectiveness of fuller's earth and Ambergard measured in vitro with pig-ear epidermal membranes was in agreement with a previous in vivo study conducted on rats. However, there was complete disparity in the ranking of decontaminants between human and pig-ear epidermal membranes measured in vitro. Thus, although pig-ear skin may be a relatively good model for predicting the human skin absorption of SM, it is a poor model for testing decontamination systems. The results of this study further validate the use of Franz-type glass diffusion cells containing human epidermal membranes as a model for predicting in vivo human skin absorption.

Aluminum Compounds↗
PubMed2005

How does the type of vehicle influence the in vitro skin absorption and elimination kinetics of terpenes?

Terpenes are widely used in the topical dermal preparations, cosmetics and toiletries and also in the experimental dermopharmacy, as penetration enhancers. Terpenes do not need to penetrate into viable skin tissue and this event is not even desired. The aim of this study was to investigate skin absorption and elimination kinetics of two terpenes, namely linalool and terpinen-4-ol, incorporated in three different dermatological vehicles: oily solution, hydrogel and o/w emulsion. The preparations were applied onto the human skin in vitro, and after 1-4 h the content of terpenes in the stratum corneum layers and in the epidermis/dermis was determined using GC. Similarly, the amounts of terpenes in the skin were analysed during 4 h elimination process following 1 h absorption. The highest skin absorption was observed when terpenes were applied in hydrogel--their total content in the skin after 4 h was 385 and 705 microg/cm2 for linalool and terpinen-4-ol, respectively. After 1 h of the elimination process about 10-20% drop of the total content of both terpenes in the skin was noted for all formulations. The skin penetration of both terpenes from the vehicles is increasing in the following order: emulsion < oily solution < hydrogel, while the elimination phase is relatively slower for terpenes applied in hydrogel.

Acyclic Monoterpenes↗
PubMed1980

The guinea-pig: an animal model for human skin absorption of hydrocortisone, testosterone and benzoic acid?

14C ring-labelled hydrocortisone, testosterone and benzoic acid dissolved in acetone were applied to the backs of guinea-pigs (4 microgram/cm2). Percutaneous absorption was quantified by following the excretion of tracer in urine and faeces for 5 days. Absorption of hydrocortisone and benzoic acid was 2.4% (s.d. = 0.5; n = 3) and 31.4% (s.d. = 9.1; n = 3) of the applied dose respectively, similar to published human absorption data. Testosterone was absorbed to a greater extent in guinea-pigs (34.9% +/- 5.4; n = 5) than man. A thioglycollate based depilatory cream significantly increased the skin absorption of testosterone, while the absorption velocity was unaltered. Two analytical methods were compared, direct counting versus wet ashing; results were in the same range for the three compounds. Two methods of quantifying skin absorption were compared; urine recovery corrected for incomplete urinary excretion after parenteral administration versus the addition of urine and faecal recovery. For benzoic acid, excreted mainly in the urine (88.1%), the two methods gave similar results; for testosterone, excreted in the urine to a lesser extent (46.8%), the method of addition of urine and faecal recovery appeared to be more correct.

Animals↗
PubMed1982

Fatal paraquat poisonings after skin absorption.

This paper reports five cases of fatal paraquat poisoning after skin absorption in adult Papua New Guinea men. Three incidents followed occupational accidents, one victim used paraquat concentrate to treat a scabies infestation, and one used it to treat head lice. All had marked blistering and excoriation, and all died from respiratory failure. In developing countries, reporting on poisoning incidents is very limited, and treatment of paraquat poisoning is, for practical purposes, nonexistent. As paraquat is not essential for tropical agriculture, its continued use should be critically reviewed.

Accidents, Occupational↗
PubMed2004

A comparison between in vitro rat and human and in vivo rat skin absorption studies.

In vitro skin penetration rates in rat and man were compared to those obtained in vivo in rats. Saturation of absorption was frequently observed at higher exposure levels in in vitro and in vivo. Lipophilic compounds showed the highest penetration rates through rat skin in vitro. In all cases in vitro dermal penetration through rat skin was higher than in vivo. Thus, the in vitro study may serve as a first tier test. The in vivo data suggest an inverse relationship between molecular weight and the rate of dermal absorption for lipophilic as well as hydrophilic compounds. Rat skin was more permeable to all tested substances than human skin (mean difference 10.9-fold). Thus, the systemic exposure of humans may be significantly overestimated if risk assessment is based only on the results of an in vivo rat study, because human skin is less permeable than rat skin. It would appear, therefore, that an estimate of actual dermal penetration through human skin should be based on the combined use of in vivo and in vitro data, using the following equation: % Human dermal penetration = (% rat in vivo dermal penetration) x (in vitro rate dermal penetration human / in vitro rate dermal penetration rat).

Animals↗
PubMed1988

Paraquat poisoning by skin absorption: a review.

All reported cases of paraquat poisoning by absorption through the skin are briefly reviewed. It is concluded that, while paraquat cannot be absorbed significantly through intact human skin, damage to the skin, either by paraquat itself or by other means, will permit greater systemic absorption and possibly poisoning. The lowest known concentration of paraquat to result in fatal poisoning through the skin is 5 g/l. Animal experiments with paraquat are also reviewed. The fact that the reported lethal dermal dose of paraquat in rats is slightly less than the oral dose is probably due to the lack of head restraint on the rats in the dermal dosing experiments. In vivo and in vitro tests on human skin at concentrations of 9 g/l and 5 g/l did not result in significant absorption of paraquat through the skin but in these experiments the skin was intact.

Animals↗
PubMed1994

Paraquat poisoning by skin absorption: report of two cases.

Two cases of paraquat poisoning resulting from skin absorption are reported. One patient died from respiratory failure 26 d after deliberate application of the herbicide onto his whole body as a treatment for scabies. The other patient developed extensive dermatitis (probably a complication of pre-existing psoriasis). Only a moderate and transitory impairment of this latter patient's renal and respiratory functions were observed after repeated exposure of his damaged skin to a dilute paraquat spray.

Adult↗
PubMed1980

Skin absorption and protective gloves in dynamite work.

Serious health hazards have been reported from dynamite manufacturing during the last hundred years but many problems are still unsolved concerning biological monitoring and protective clothing. In this study, experiments are reported where ethylene glycol dinitrate (EGDN) has been measured in blood from subjects whose hands were exposed to dynamite vapors only or to the combination of vapors and the solid phase, with an without gloves. Strong indications were found that skin absorption is a major route of entry for EGDN into the body. Rubber gloves were found to absorb considerable amounts of EGDN and also to let it pass thorugh to the skin and the blood. However, rubber gloves with inner cotton gloves seem to constitute some protection if they are changed as frequently as once or twice an hour compared with only using cotton gloves or working bare-handed. Blood samples from cubital veins primarily were found to reflect the local skin absorption of EGDN and not the total uptake. Exhaled air was analyzed at moments of high skin exposure but no EGDN could be detected. Further studies of biological monitoring and protective materials are suggested.

Air Pollutants↗
PubMed1990

In vitro skin absorption and metabolism of benzoic acid, p-aminobenzoic acid, and benzocaine in the hairless guinea pig.

The percutaneous absorption and metabolism of three structurally related compounds, benzoic acid, p-aminobenzoic acid (PABA), and ethyl aminobenzoate (benzocaine), were determined in vitro through hairless guinea pig skin. Benzocaine was also studied in human skin. Absorption of benzocaine was rapid and similar through both viable and nonviable skin. The absorption of the two acidic compounds, benzoic acid and PABA, was greater through nonviable skin. A small portion (6.9%) of absorbed benzoic acid was conjugated with glycine to form hippuric acid. Although N-acetyl-benzocaine had not been observed as a metabolite of benzocaine when studied by other routes of administration, both PABA and benzocaine were extensively N-acetylated during percutaneous absorption. Thus, the metabolism of these compounds should be considered in an accurate assessment of absorption after topical application.

4-Aminobenzoic Acid↗
PubMed1989

Exposure to paraquat through skin absorption: clinical and laboratory observations of accidental splashing on healthy skin of agricultural workers.

Data concerning 15 consecutive cases of single exposures of the skin or eyes during work to paraquat solutions are presented. Urine and serum were analysed for paraquat in all these cases at the laboratory of the Israel Poison Information Center. From these data it is apparent that a single exposure of healthy skin to paraquat solutions caused only local lesions. No systemic effect was detected in these patients.

Administration, Topical↗
PubMed2002

In vivo measurement of human skin absorption of topically applied substances by a photoacoustic technique.

A photoacoustic technique is used for studying topically applied substance absorption in human skin. The proposed method utilizes a double-chamber PA cell. The absorption determination was obtained through the measurement of the thermal effusivity of the binary system substance-skin. The theoretical model assumes that the effective thermal effusivity of the binary system corresponds to that of a two-phase system. Experimental applications of the method employed different substances of topical application in different parts of the body of a volunteer. The method is demonstrated to be an easily used non-invasive technique for dermatology research. The relative concentrations as a function of time of substances such as ketoconazol and sunscreen were determined by fitting a sigmoidal function to the data, while an exponential function corresponds to the best fit for the set of data for nitrofurazona, vaseline and vaporub. The time constants associated with the rates of absorption, were found to vary in the range between 10 and 58 min, depending on the substance and the part of the body.

Acoustics↗
PubMed2005

Effect of physicochemical properties of cyclic terpenes on their ex vivo skin absorption and elimination kinetics.

BACKGROUND: The terpenes disturb lipid arrangement in the intercellular region of the stratum corneum (SC) that leads to the increased permeability of the skin. This effect is used in technology of transdermal drug forms and depends on physicochemical properties of terpenes and their amounts penetrated to the stratum corneum; however terpenes do not need penetrate into viable skin tissue and this event is not even desired. OBJECTIVE: To correlate skin absorption and elimination kinetics of four cyclic terpenes, namely alpha-pinene, beta-pinene, eucalyptol and terpinen-4-ol, applied as neat substance with their physicochemical properties. METHODS: The terpenes were applied onto the human skin in vitro, and after 1-4 h their content in the separated by a tape-stripping method stratum corneum layers and in the epidermis/dermis was determined using GC. Similarly, the amounts of terpenes in the skin were analysed during 4 h following 1 h absorption. RESULTS: The fastest and progressive penetration into all skin layers was observed for terpinen-4-ol. All studied terpenes are absorbed in the viable epidermis/dermis, however penetration into this layers is time-dependent process, constantly increasing during 4 h. Like for stratum corneum, the largest cumulation in epidermis/dermis was observed for terpinen-4-ol. The elimination of terpenes from the stratum corneum was fast, especially in deeper layers, and much faster if the initial cumulation was small. CONCLUSION: Investigated cyclic terpenes represent different penetration and elimination characteristics and do not permeate across the skin to the acceptor medium due to large cumulation in the skin tissue. The penetration of terpenes into stratum corneum is greater if their log P-value is close to 3.

Adult↗