Donald R. Wilson

Transepidermal Water Loss in vivo

In vivo , noninvasive, transepidermal water loss measurements were taken from 26- to 41-week gestational age infants with a Meeco® electrolytic water analyzer to yield information on

The relationship of pKa and acute skin irritation in man.

The relationship between pKa and skin irritation in man is studied for a homologous series of benzoic acid derivatives, which permeate through human skin at comparable rates (15–88 µg/cm2/hr). Skin irritation and pKa are correlated for pKa ≤ 4. Laser Doppler velocimetric assessment of skin blood flow, color meter readings, erythema, edema, and the primary irritation index are all linearly correlated and related to pKa, erythema at 24 hr appears to be the most sensitive parameter to variation in pKa when pKa ≤ 4.

The local side effects of transdermally absorbed nicotine

Percutaneous nicotine administration induces predominant sudorific and rubiform responses in the skin which may be accompanied by subtle piloerection, hyperalgesia and pruritus (although these signs are not overtly manifest). These dermal responses are complex and mechanisms have been proposed for the direct nicotine-stimulation of sweat glands, piloerection and vasoconstriction. These reactions are accompanied by secondary activation and release of vasodilator peptides which produce a predominating vasodilator tone following topical administration, this response masking the direct axon reflex-mediated vasoconstriction.

Skin wound healing determined by water loss

An in vivo method of monitoring healing was tested incorporating an Evaporimeter measuring water evaporation; reepithelialization was detected through reestablishment of the water barrier. In the first study two wounds were created with a 2-mm biopsy punch on each of the backs of 15 rabbits and covered with occlusive and semiocclusive dressings. Water loss increased from a preoperative value of 6 g m-2 hr-1 to 55 g m-2 hr-1 after surgery. Water loss from the occluded site returned to baseline values in 9 days as opposed to 17 days for the semioccluded sites (P less than 0.05). The second study followed the healing of full-thickness 4 X 4-cm wounds in five rabbits treated with fine-mesh gauze and five treated with a human amnion dressing. Wound area and water loss were observed during the repair process. Visually measuring the wound area, the injuries appeared 100% healed on Day 30. The Evaporimeter continued to detect significantly increased water loss up until Day 45 when the original baseline values were reached. No differences were observed between the gauze and amnion groups. The Evaporimeter presents a simple yet accurate, noninvasive tool measuring the wound healing endpoint based on regeneration of the epidermal water barrier.

The Relationship between pKa and Skin Irritation for a Series of Basic Penetrants in Man

For a series of bases, which penetrate through human skin in vitro at similar rates (0.056-0.49 microM/cm2/hr), penetrant pKa is shown to correlate with erythema, edema, and color meter readings. As estimates of irritation, erythema, edema, and redness measurements are highly linearly correlated. For the selected series, irritation becomes significant for bases with a pKa greater than 8. The irritation potential of acids with pKa less than or equal to 4 has been previously reported; pKa appears highly predictive of acute skin irritation for acids and bases in man.

Relationship of PKA and Acute Skin Irritation in Humans

AbstractThe relationship between pKa and skin irritation in humans was studied for a homologous series of benzoic acid derivatives with predicted permeation through human skin at comparable rates (15-90 μg/cm2/hr). Skin irritation and pKa are strongly correlated, and, for pKa ≤4, skin irritation rapidly increases. Laser Doppler velocimetric assessment of skin blood flow, color meter readings, erythema, edema, and the primary irritation index are all linearly correlated and related to pKa; erythema at 24 hr appears to be the most sensitive variable.