Acute Dermal Irritation test (Draize Skin test). EN-ISO 10993-23: 2021. Biological Evaluation of Medical Devices. Part 23: Irritation tests.

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The ISO 10093-23:2021 standard describes irritation tests for the evaluation of medical devices, components of medical devices, biomaterials or their extracts. The principle of the Acute Skin Irritation Test (Draize) is the evaluation of the potential of the test material to produce dermal irritation by applying it to the skin of rabbits, as a suitable animal model.

The ISO 10993-23 standard requires the dosage of 3 experimental animals (rabbits) by the cutaneous route with the test product or with its extract. To prepare the extracts, polar (physiological saline solution, distilled water, 58% hydroalcoholic solution) and non-polar (vegetable oils) solvents are used.

The test is usually carried out with a single dose, but if the clinical use of the test product requires it, a repeated-exposure test can be carried out after the completion of an acute single exposure test. If the repeated exposure test is requested, the number of exposures to be performed must be indicated, taking into account that the repeated exposure must be limited to the clinical use of the test product.

For single exposure tests, the appearance of the test substance application sites is recorded and scored, assigning them a gradation (0-4), based on the erythema and oedema reactions observed at 24, 48 and 72 hours. With these values, the Primary Irritation Index is calculated to determine the irritating effect of the product. For repeated exposure tests, the reaction observed at the test sites one hour after each application, immediately before the next, and 1, 24, 48 and 72 hours after the last application is recorded and the Cumulative Irritation Index. The value of the Primary or Cumulative Irritation Index, as appropriate, will determine if the test product has a severe, moderate, slight irritant effect, or if it is negligible. If lesions are observed, in any of the tests, the observation of the animals can be extended up to 14 days to study the reversibility or irreversibility of the lesions, with daily observations of the animals. It should be noted that the evaluation of strongly acid or alkaline substances (with pH 2 or less, or pH 11.5 or higher) is not required and the test product shall be considered an irritant.