Solvent effects in permeation assessed in vivo by skin surface biopsy

BACKGROUND: Transdermal drug delivery has become an important means of drug administration. It presents numerous advantages but it is still limited by the small number of drugs with a suitable profile. The use of solvents that affect the skin barrier function is one of the classic strategies of penetration enhancement. Some of these solvents have well characterised actions on the stratum corneum, but the majority are still selected using empirical criteria. The objective of this work was to conduct a systematic study on the ability to affect skin permeation of solvents commonly used in transdermal formulations. An innovative methodology in this area was employed, consisting of the combination of skin surface biopsy with colorimetry. METHODS: The study compared in vivo differences in the permeation of a hydrophilic (methylene blue) and a lipophilic (Sudan III) dye, after treatment of the skin with different vehicles. Consecutive skin surface biopsies of each site were taken and the cumulative amounts of the dyes in the stripped stratum corneum were measured by reflectance colourimetry. RESULTS: Results indicate that the amount of methylene blue present in the stratum corneum varied significantly with different skin pre-treatments. Some solvents provided a 1.5 fold penetration enhancement but others decreased by almost half the permeation of the dye. The permeation of Sudan III was less significantly affected by solvent pre-treatment. CONCLUSIONS: This study has only superficially explored the potential of the combination of skin surface biopsy and colourimetry, but the encouraging results obtained confirm that the methodology can be extended to the study of more complex formulations

Oxygenated-Blood Colour Change Thresholds for Perceived Facial Redness, Health, and Attractiveness

Blood oxygenation level is associated with cardiovascular fitness, and raising oxygenated blood colouration in human faces increases perceived health. The current study used a two-alternative forced choice (2AFC) psychophysics design to quantify the oxygenated blood colour (redness) change threshold required to affect perception of facial colour, health and attractiveness. Detection thresholds for colour judgments were lower than those for health and attractiveness, which did not differ. The results suggest redness preferences do not reflect a sensory bias, rather preferences may be based on accurate indications of health status. Furthermore, results suggest perceived health and attractiveness may be perceptually equivalent when they are assessed based on facial redness. Appearance-based motivation for lifestyle change can be effective; thus future studies could assess the degree to which cardiovascular fitness increases face redness and could quantify changes in aerobic exercise needed to increase facial attractiveness

The Inflammatory Hypothesis of Ageing: Fascinating Concept or Confusing Dogma?

peer reviewe

Dandruff-associated smouldering alopecia: a chronobiological assessment over 5 years.

BACKGROUND: In some individuals, dandruff may be recurrent and even chronic. This represents a difficult-to-treat condition. Excessive hair shedding and diffuse alopecia may develop. OBJECTIVES: To evaluate the chronobiological aspects of dandruff, hair shedding and alopecia. METHODS: This study was performed in eight men suffering from such a scalp condition. They were examined 40 times at regular intervals for five consecutive years. Hair-density assessments and trichograms were performed at least twice per trimester on the parietal region of the scalp, corresponding to an area where dandruff was present. RESULTS: A positive correlation was found between the percentage of telogen hairs and dandruff severity as assessed by the squamometry index. Bimodal yearly biorhythms were found for dandruff severity, telogen counts and hair loss between two consecutive visits. The chronobiological fluctuations were prominent in some study participants, but remained inconspicuous in others. The biorhythms were almost synchronized in all participants, showing variations over the year. CONCLUSIONS: The biorhythms on the hair cycle in dandruff are not fundamentally different from those previously reported in subjects without dandruff. The periodicity may be an intrinsic feature of human skin