Hair Casts

Kligman, Albert M.

doi:10.1001/archderm.1957.01550160035004

Cited by 50 publications

(11 citation statements)

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“…This study (1) confirmed the slow rate of urea crystallization in an LEC formulation when compared with an NS formulation and urea aqueous solution under winter-like low humidity conditions (humidity: 40-50%; temperature: 20-25°C).…”

Section: Discussionsupporting

confidence: 72%

“…The softening effect on the stratum corneum generally increases with the urea content of the cream. 1,2) Urea is more readily transferred to the stratum corneum in the dissolved (amorphous) state 3) and exhibits higher clinical efficacy when compared to crystalline urea; consequently, preparations are formulated to suppress crystallization 4) and thus maintain easy absorption. 5) External preparations that crystallize post-application exhibit drastically decreased transfer of urea to the skin 6) and may feel taut or gritty, and irritate the skin.…”

mentioning

confidence: 99%

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Deposits from Creams Containing 20% (w/w) Urea and Suppression of Crystallization (Part 1): Rate of Crystallization from Cream Containing 20% (w/w) Urea and Evaluation of the Properties of the Deposit

Goto

Morita

Terada

2016

CHEMICAL & PHARMACEUTICAL BULLETIN

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Two creams containing 20% (w/w) urea and various emulsifiers, a nonionic surfactant (NS) and lecithin (LEC), were prepared, and the rate of crystallization following application of the cream and differences in the properties of the deposits were investigated. Post-application crystallization was slower with the LEC formulation. Differences in the crystals obtained from the two formulations and from a 20% aqueous solution of urea were evaluated by powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), powder X-ray-DSC (PXRD-DSC) and Fourier transform infrared spectrophotometry (FT-IR). PXRD and PXRD-DSC measurements showed that the diffraction patterns of both formulations differed from that of urea. The NS formulation provided diffraction peaks for urea and a urea composite, whereas only the urea composite was evident in the LEC formulation. DSC scans of urea showed an endotherm at around 134°C, whereas the deposits from both formulations provided an endotherm 23-25°C below that of urea; the NS formulation also showed a peak at around 140°C. These results indicate a tendency for urea crystallization in the NS formulation. FT-IR measurements showed that both deposits have a urea-based structure. The effects of the LEC formulation components on the physical properties of urea were investigated by PXRD and showed that all diffraction peaks were evenly weakened, suggesting that urea tends to be amorphous and that the formulation impacts post-application urea crystallization. Consequently, the amorphous state of urea can be maintained post-application by optimizing the formulation, thereby increasing the clinical efficacy of the cream.

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Section: Discussionsupporting

confidence: 72%

mentioning

confidence: 99%

Deposits from Creams Containing 20% (w/w) Urea and Suppression of Crystallization (Part 1): Rate of Crystallization from Cream Containing 20% (w/w) Urea and Evaluation of the Properties of the Deposit

Goto

Morita

Terada

2016

CHEMICAL & PHARMACEUTICAL BULLETIN

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“…[78] This characteristic is of paramount importance in their diagnosis and helps in differentiating them from other scalp disorders, such as pediculosis capitis, piedra, trichomycosis, trichonodosis and trichorrhexis nodosa. [9–11] As is often the case, hair casts may initially be misdiagnosed as the nits of pediculosis capitis [Table 1].…”

Section: Discussionmentioning

confidence: 99%

Hair casts or pseudonits

et al. 2011

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“…The keratin-softening effect increases with increasing urea content in externally applied formulations and with increasing urea uptake by the stratum corneum. 7) The effects of the formulation base and form on the course of percutaneous absorption and transfer to the stratum corneum are readily apparent. It is accordingly essential to determine the amount of urea transferred to the stratum corneum during urea formulation development.…”

mentioning

confidence: 99%

Deposits from Creams Containing 20% (w/w) Urea and Suppression of Crystallization (Part 2): Novel Analytical Methods of Urea Accumulated in the Stratum Corneum by Tape stripping and Colorimetry

Goto

Morita

Terada

2016

CHEMICAL & PHARMACEUTICAL BULLETIN

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The transfer of urea from a urea formulation to the stratum corneum varies with the formulation base and form, and impacts the formulation's therapeutic effect. Consequently, determining the amount of urea transferred is essential for developing efficient formulations. This study assessed a simple method for measuring the amount of urea accumulated in the stratum corneum. Conventional methods rely on labeling urea used in the formulation with radiocarbon ( 14 C) or other radioactive isotopes (RIs), retrieving the transferred urea from the stratum corneum by tape stripping, then quantitating the urea. The handling and use of RIs, however, is subject to legal regulation and can only be performed in sanctioned facilities, so methods employing RIs are neither simple nor convenient. We therefore developed a non-radiolabel method "tape stripping-colorimetry (T-C)" that combines tape stripping with colorimetry (urease-glutamate dehydrogenase (GLDH)) for the quantitative measurement of urea. Urea in the stratum corneum is collected by tape stripping and measured using urease-GLDH, which is commonly used to measure urea nitrogen in blood tests. The results indicate that accurate urea measurement by the T-C method requires the application of 1400 mg (on hairless rats) of a 20% urea solution on a 50 cm 2 (5 10 cm) area. Further, we determined the amount of urea accumulated in the stratum corneum using formulations with different urea concentrations, and the time course of urea accumulation from formulations differing in the rate of urea crystallization. We demonstrate that the T-C method is simple and convenient, with no need for 14 C or other RIs.

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Hair Casts

Cited by 50 publications

References 0 publications

Deposits from Creams Containing 20% (w/w) Urea and Suppression of Crystallization (Part 1): Rate of Crystallization from Cream Containing 20% (w/w) Urea and Evaluation of the Properties of the Deposit

Deposits from Creams Containing 20% (w/w) Urea and Suppression of Crystallization (Part 1): Rate of Crystallization from Cream Containing 20% (w/w) Urea and Evaluation of the Properties of the Deposit

Hair casts or pseudonits

Deposits from Creams Containing 20% (w/w) Urea and Suppression of Crystallization (Part 2): Novel Analytical Methods of Urea Accumulated in the Stratum Corneum by Tape stripping and Colorimetry

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