Penetration enhancement water

W. S. Halliday and D. K. Clapper. Purified paraffins as lubricants, rate of penetration enhancers, and spotting fluid additives for water-based drilling fluids. Patent US 5837655, 1998. 

Since the discovery of synthetic dye by Perkin and the establishment of the synthetic organic chemistry industry, a wide variety of synthetic dyes provided a set of choices for staining microbes so that they could be readily examined under the microscope. It is reasonable to suppose that if a dye binds selectively to a microbe much more than to mammalian tissues, then it may be possible to find a dye that selectively harms the microbe and spares the mammal. Paul Ehrlich (figure 1.6) was a medical student who did research in the distribuhon of foreign substances in the body, and he was particularly interested in the influence of chemical structures of different types of molecule in live animals. He observed that acidic dyes with the sulfonic acid function, used by dye manufacturers to enhance water solubility, were unable to penetrate into the brain or fat tissues. 

Urea is a hydrating agent (a hydrotrope) used to treat scaling conditions such as psoriasis, ichthyosis, and other hyperkeratotic skin conditions. Applied in a water-in-oil vehicle, urea alone or in combination with ammonium lactate hydrated stratum corneum and improved barrier function when compared to the vehicle alone in human volunteers in vivo [45], Urea also has keratolytic properties, usually when combined with salicylic acid for keratolysis. The somewhat modest penetration-enhancing activity of urea probably arises from a combination of increasing stratum corneum water content (water is a valuable penetration enhancer) and through the keratolytic activity. 

Southwell, D., and B.W. Barry. 1983. Penetration enhancers for human skin Mode of action of 2-pyrrolidone and dimethylformamide on partition and diffusion of model compounds water, -alcohols and caffeine. J Invest Dermatol 80 507. 

Morimoto, EL, et al. 2002. In vitro skin permeation of morphine hydrochloride during the finite application of penetration-enhancing system containing water, ethanol and 1-menthol. Biol Pharm Bull 25 134. 

J. Engblom, S. Engstrom, and K. Fontell, The effect of the skin penetration enhancer Azone on fatty acid-sodium soap-water mixtures, J. Control. Rel. 33 299— 305 (1995). 

It is of course not only the concentration of water that may be deduced by this methodology in fact, any penetrant possessing a characteristic IR signature, distinct from the SC components, can be similarly monitored. Consequently, one of the noteworthy uses of reflectance spectroscopy has been the in vivo evaluation of penetration enhancement, both in the assessment of enhancer efficacy and in the investigation of their mode of action. The basis of this research, however, lies in the extensive in vitro investigations, by IR and DSC, of penetration enhancer activity and it is therefore pertinent to first review the principal literature. 

Observations of this nature are not unique to water, and a diverse range of penetration enhancers has been found to modify the phase transitions of human SC components, albeit selectively and to varying degrees. What is the significance of these findings, and how might they be interpreted in relation... 

Particle size and particle size distribution studies are important for drugs that have low water solubility. Particle size reduction by milling to a micronized form increased the absorption of low aqueous solubility drugs such as griseofulvin, nitrofurantoin, and many steroids. Smaller particle size results in an increase in the total surface area of the particles, enhances water penetration into the particles, and increases the dissolution rates. With poorly soluble drugs, a disintegrant may be added to the formulation to ensure rapid disintegration of the tablet and release of the particles. 

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