Rosacea: An Introduction

Example 13 - Testing Procedure for Prevention of Redness

Testing Procedure for Prevention of Redness by .alpha.-Adrenergic Agonists:

A number of .alpha.-adrenergic agonists were evaluated for their ability to topically suppress erythema in human skin induced by methyl nicotinate. The erythema produced in the skin results from the vasodilatory effect on the dermal vasculature by methyl nicotinate. In this model, the minimum erythemal dose (MED) produced on the forearm by methyl nicotinate is determined for each test subject. The MED is defined as the minimal dose that results in a defined circle of erythema. The MED was determined by saturating five 19 mm Hill Top Chambers with 220 .mu.l of 1, 2, 3, 4, and 5 mm methyl nicotinate. The Hill Top Chambers were applied to the volar forearm of each test subject, removed after 30 seconds and excess liquid lightly blotted from the skin. The MED of methyl nicotinate was selected 10 minutes after application, by determining the minimal dose that resulted in a defined circle of erythema. The .alpha.-adrenergic agonists were dissolved in alcohol and topically applied (2 .mu.l/cm.sup.2) to selected sites on the contralateral volar forearm for 30 minutes prior to challenge with methyl nicotinate. Hill Top Chambers (19 mm) were saturated with 220 .mu.l of the dose of methyl nicotinate determined to produce a MED for each test subject. The chambers were applied to the volar forearm treated with vehicle or test compounds, removed after 30 seconds and excess liquid was lightly blotted from the skin. Ten minutes after application of methyl nicotinate the test sites were evaluated for erythema. A numerical grading scale of 0 to 3 was used: 0=none, 0.5=barely perceptible, 1.0=mild, 1.5=mild+(mild to moderate), 2.0=moderate, 2.5=moderate+(moderate to severe), 3.0=severe.

The test results are shown in the table below and indicate that each of the tested compounds reduced the formation of the Methyl Nicotinate induced redness (erythema) in the test subjects. With both Oxymetazoline HCl and Naphazoline HCl the redness was fully blocked for two of the three subjects pursuant to the test conditions as described above.

The Effect of .alpha.-Adrenergic Agonists on Methyl Nicotinate-Induced Erythema Pre-Treatment + Methyl Nicotinate N Mean Erythema Grade Alcohol Vehicle Control 3 3.0 0.2% Naphazoline HCl 3 0.33 0.2% Oxymetazoline HCl 3 1.0 0.2% Brimonidine 3 0.83


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