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[Solubility in water and skin absorptive toxicity of pesticides].

One parameter equation connected skin-resorptive toxicity of pesticides and its solubility in water was maintained. For defoliants, insecticides, acaricides, nematocides and zoocides a good correlation between calculated and experimental values of skin-resorptive toxicity for rats was shown.

Administration, Cutaneous

[Saturnism caused by skin absorption of a drug].

A case of chronic lead poisoning is described in a woman presenting with abdominal pain due to cutaneous absorption of a lead soap. We have found no other case of intoxication by this route in the literature.

Administration, Topical

Skin absorption enhancers.

When we try to maximize drug flux through the skin, we usually meet major difficulties because of the impervious nature of the stratum corneum. A popular solution incorporates penetration enhancers into transdermal products. Such materials ideally possess the sole property of reversibly reducing the barrier resistance of the horny layer, allowing the drug to reach the living tissues at a greater rate. This article considers examples of accelerant action that support a general concept explaining enhancer activity in human skin. The core of the proposal is that enhancers usually work by one or more of three main mechanisms: alteration of the lipid or protein domains of the stratum corneum or increase in tissue partitioning of a drug, a coenhancer, water, or any combination of these three chemicals. We may usefully refer to the overall hypothesis as the lipid-protein-partitioning (LPP) concept.

Administration, Cutaneous

Skin absorption and cutaneous first pass metabolism of topical steroids: in vitro studies with mouse skin in organ culture.

Using mouse skin maintained in a permeability chamber-organ culture system, we have examined the percutaneous penetration and cutaneous fate of some selected steroids. At 16 hr after in vitro topical application (10 micrograms/2 cm2), the extent of permeation of the selected steroids was testosterone (65.13%) much greater than cortisol (18.1%) = estradiol (18.0%) greater than estrone (10.58%) much greater than estriol (2.45%). Permeation was accompanied by cutaneous first pass metabolism. In addition to water-soluble metabolites, other metabolites found in the perfusion medium from topical testosterone included 5 alpha-dihydrotestosterone, 5 alpha-androstanedione and androstenedione. Cortisone was identified as one of the metabolites of topical cortisol. For the estrogens, estradiol and estriol were metabolites of topical estrone, whereas estrone and estriol were metabolites of topical estradiol. The extent of cutaneous first pass metabolism of these selected steroids varies considerably. Estrone was metabolized extensively, but only limited metabolism of estradiol and cortisol was observed during their translocation through the skin. With testosterone, it was evident that an increase in the topically applied dose was accompanied by a decrease in the relative extent of both permeation and cutaneous first pass metabolism. However, cutaneous first pass metabolism of estriol was essentially negligible. These observations demonstrated that both diffusional and metabolic processes are important in the percutaneous fate of topical steroids. They also suggest that in future studies concerned with the absorption and bioavailability of topically applied chemicals, an assessment of the drug-metabolizing capabilities of the skin needs to be considered.

Administration, Cutaneous

Enhancement of propranolol hydrochloride and diazepam skin absorption in vitro: effect of enhancer lipophilicity.

The enhancement of model hydrophilic (propranolol hydrochloride) and lipophilic (diazepam) drug penetration across rat and hairless mouse skin in vitro has been studied. Preliminary experiments established that most n-alkanes having chain lengths of between 7 and 16 promote the flux of both drugs. For propranolol, enhancement varied parabolically with carbon number; for diazepam, heptane was ineffective and all others were essentially equipotent. Enhancement by n-nonane was then compared with that by n-nonanol. Propranolol flux was increased by both enhancers, whereas diazepam penetration was not affected by the less lipophilic alcohol. The enhancement of propranolol by n-nonane and n-nonanol was examined as a function of adjuvant concentration in the applied formulation. Maximum increases in maximum penetration rates of 6.5-fold (n-nonane) and 8.2-fold (n-nonanol) were determined. As expected, the enhancement was saturable, indicative of a maximally perturbed stratum corneum. Finally, the penetration enhancing abilities of six monoterpenes were assessed. The purely hydrocarbon analogues promoted both propranolol and diazepam transport to an extent similar to that of n-nonane. The terpenes with hydrogen-bonding ability, however, only enhanced propranolol flux (at a level comparable to n-nonanol). While the data reported do not directly reveal mechanistic information on percutaneous penetration enhancement, they do provide a starting point for the rational investigation of interrelationships between drug, enhancer, and skin. Such information is clearly essential for the optimization and exploitation of transdermal drug delivery.

Alkanes