Info Xny
Melia CD, Cutts LS, Adler J, Davies MC, Hibberd S, Rajabi-Siahboomi AR, Bowtell R. Visualising and measuring dynamic events inside controlled release matrix systems. Proc Int Symp Controlled Release Bioact Mater 22 32-33, 1995. Cutts LS, Roberts PA, Adler J, Davies MC, and Melia CD. The measurement of diffusion coefficients in gels using the confocal laser scanning microscope. In Hadgraft J, Kellaway IW, Parr GD, eds. Proceedings of the 3rd UKaps Conference, p 54, 1994. Hadgraft J, Ridout G....
References Afh
1. Federal Register. Requests for proposals for enforceable consent agreements dermal absorption rate testing of eighty OHSA chemicals solicitation of interested parties text of protocol. April 3, 61 65 1996. 2. Walker JD, Whittaker C, McDougal JN. Role of the TSCA interagency testing committee in meeting the U.S. government data needs designating chemicals for percutaneous absorption rate testing. In Marzulli FN, Maibach HI, eds. Dermatotoxicology, 5th ed. Washington, DC Taylor amp Francis, pp...
Info Cci
Alonso A, Meirelles NC, Tabak M. Effect of hydration upon the fluidity of intercellular membranes of stratum corneum an EPR study. Biochim Biophys Acta 1237 6-15, 1995. Alonso A, Meirelles NC, Yushmanov VE, Tabak M. Water increases the fluidity of intercellular membranes of stratum corneum correlation with water permeability, elastic, and electrical resistance properties. J Invest Dermatol 106 1058-63, 1996. Wiedmann TS. Influence of hydration on epidermal tissue. J Pharm Sci 77 1037-1041,...
References Vxk
1. Halkier-Sorensen L. Occupational skin disease. In Roberts MS, Walters KA, eds. Dermal Absorption and Toxicity Assessment. New York Marcel Dekker, pp 127-154, 1998. 2. Cross SE. Topical therapeutic agents used in wound care. In Roberts MS, Walters KA, eds. Dermal Absorption and Toxicity Assessment. New York Marcel Dekker, pp 415442, 1998. 3. Roberts MS, Walters KA. The relationship between function and barrier function of the skin. In Roberts MS, Walters KA, eds. Dermal Absorption and...
Info Amw
Cp kgFdose r____r 75 Hence, the logarithm of the plasma concentration should be linearly related to the time after application over very long times. The urinary excretion rate is an alternative pharmacokinetic representation amount of drug in the body with time. Beckett et al. 176 showed that time to peak urinary excretion rate was longer and the actual peak height lower for transdermal applications than for the oral route. A comparison of the loglinear profiles for the oral and transdermal...
Preface
The past two decades have witnessed brilliant discoveries regarding the structure andfunc-tions of the stratum corneum. An immense amount of research has been carried out over the past two decades on the micromorphology of the skin, in particular of the stratum corneum, and the important role that this organ plays in the maintenance of human life. It has also been nearly two decades since the publication of Brian Barry's book Dermatological Formulations Percutaneous Absorption. This book...
S 1
Solubility, in this chapter, unless otherwise specified, is defined by a phase being saturated with solute such that the chemical potential of the dissolved solute M satm-ated Mpure. As a number of studies have applied various approaches used to determine solubility in the prediction of percutaneous penetration flux, we now consider the prediction of solubility using these approaches in further detail. 1. Conventions Used for Prediction of Solubility, Partition Coefficient, and Flux It should...
Info Rhw
aBased on it having a solubility parameter of 14.0 cal cm3 1'2 and a molar volume of 110 cm3 mol, the stratum corneum having a solubility parameter of 10 cal cm3 1'2 Source Ref. 62. aBased on it having a solubility parameter of 14.0 cal cm3 1'2 and a molar volume of 110 cm3 mol, the stratum corneum having a solubility parameter of 10 cal cm3 1'2 Source Ref. 62. cept to describe the permeation of solutes through the skin. Ruelle et al. 69 have suggested that both the usual solubility parameter...
Artificial Cultured Skin
The technology behind the construction of human skin equivalents artificial skin is derived predominantly from research into the treatment of burns. A classification and evaluation of the numerous different types of human skin equivalents concluded that the technique is limited to the reconstitution of the epidermis with a SC 171 . Such models have been used to investigate both cutaneous metabolic events 131,132,172 and dermal irritation 173 , with varying degrees of success. The use of...
T T 1
Hence, the solute solubility Xt is enhanced either by the solute's lower-melting point first term in right hand side of Eq. 11 becomes zero when the solute is a liquid i.e., Tm lt T or by choosing a solvent with a solubility parameter close to that of the solute so that 8, 81 is minimized. We now use the foregoing concepts to derive the SC-vehicle partition coefficient Ksc-v . Substituting Eq. 11 into Eq. 7 yields for the SC and for a vehicle 62 ln K,c-v ln jv- ln j 8 - 8 2 - 8 - 8 2 13 If low...
Vi Transappendageal Transport
The role of appendages in skin transport has been controversial and remains so. The earliest evidence to support the existence of the transfollicular route of transdermal Figure 32 A Correlation between in vivo and in vitro transdermal drug flux each datapoint represents a different drug, dashed line indicates perfect correlation between in vivo and in vitro transdermal drug flux B fraction of total concentration of topically applied methylsalicylate determined in microdialysate or in vitro...
Iii Principles Of Skin Transport
The process of percutaneous absorption involves several individual transport processes, some of which occur in series and others in parallel see Fig. 3 . The two key determinants for a solute crossing a membrane are solubility and diffusivity. The relative solubility of a solute in two phases determines its partition coefficient and, therefore, the likelihood of the solute being taken up into the SC from a vehicle. Also, solubility will determine whether a solute is likely to be desorbed from...
Viii Solar Keratoses
Solar actinic keratoses present as scaling hyperkeratotic plaques or papules on skin exposed to light. They are most commonly seen on elderly subjects with fair skin who have had high levels of ultraviolet exposure over many years. They may be associated with other signs of photodamage such as yellowing, coarsening, and wrinkling of the skin. Individuals with large numbers of solar keratoses are at increased risk of developing nonmelanoma skin cancer. Histologically, the lesions show epidermal...
I Introduction
The skin is the largest organ of the body, accounting for more than 10 of body mass, and the one that enables the body to interact most intimately with its environment. Figure 1 shows a diagrammatic illustration of the skin. In essence, the skin consists of four layers the stratum corneum nonviable epidermis , the remaining layers of the epidermis viable epidermis , dermis, and subcutaneous tissues. There are also several associated appendages hair follicles, sweat ducts, apocrine glands, and...
A The Epidermis
The epidermis performs a number of functions, as shown in Figure 3, one of the most important being the generation of the stratum corneum, as described later. The stratum corneum is the heterogeneous outermost layer of the epidermis and is approximately 10-20 m thick. It is nonviable epidermis and consists, in a given cross-section, of 15-25 flattened, stacked, hexagonal, and cornified cells embedded in a mortar of intercellular lipid. Each cell is approximately 40 m in diameter and 0.5 m...
Treatment of Scalp Psoriasis
Scalp psoriasis, similar to psoriasis elsewhere, will respond to a similar range of topical therapy although the presence of hair makes treatment more difficult. Application is messy. For thick plaques on the scalp topical therapies include oil of cade, ung. cocois,'' and combinations of coal tar and salicylic acid such as 6 coal tar and 3 salicylic acid , all of which are effective at removing scale and settling inflammation. These preparations may be applied to the scalp and left on overnight...
B Atopic Eczema Dermatitis
The etiology of atopic eczema is unknown. Patients have increased levels of serum IgE and some have precipitating antibodies to environmental allergens, including foods and inhaled materials. Many patients will have a positive response to intracutaneous challenge with pollen, house dust mite, cat fur, and fish antigens. However, the significance of these positive reactions is unclear. Patients with atopic eczema have reduced numbers of circulating T-suppressor cells which are responsible for...
C Biochemical Abnormalities
There are a large number of diseases that can affect epidermal barrier function, and it is beyond the scope of this chapter to consider any of these in great depth. Some of the diseases affect the formation of the corneocyte ''broken brick syndrome'' whereas other affect the intercellular lipid ''weak mortar syndrome'' . For instance, Nemes and Steinhardt 66 refer to more than ten different diseases involving genes that encode keratin intermediate filaments, including Unna-Thost disease and...
B Chemical Damage
When the stratum corneum is perturbed, several localized biochemical events occur that result in rapid reconstitution of barrier function 64,129-137 . Thus, in extreme cases of stratum corneum damage, such as acetone-induced delipidation 129-131 or tape-stripping 137 , there appears to be a biphasic pattern of recovery a rapid phase of repair, followed by a slower phase of normalization. The initial rapid phase of barrier recovery involves the expeditious secretion of preformed lamellar bodies...