Standard Practice for Guinea Pig: Split Adjuvant and Closed Patch Testing for Contact Allergens
This practice is intended to determine the potential for a substance, or material extract, to elicit contact dermal allergenicity. It is intended as an alternative to the Guinea Pig Maximization Test (GPMT), given the limitations on dosage form and tendency for false positives associated with the latter test. The split adjuvant method is used when topical application is considered relevant, and the dosage form is a solid, liquid, extract, paste, or gel. The method includes four induction doses applied over a period of time to the same shaved or depilated site on guinea pigs, followed by occlusive patching. Freund's Complete Adjuvant (FCA) is injected near the dose site on a specific time, (second induction dose). Following a rest period, animals are challenged at a previously unexposed site, and the reaction evaluated at regular intervals. The closed patch method is used when topical application is relevant, but the preferred dosage form does not permit injection under the skin or intradermally, and the discomfort involved with extended occlusive patching and adjuvant use is to be avoided. It involves repeated induction doses over a period of time at the same shaved/depilated site, followed each time by occlusive wrapping. After a rest period, animals are challenged at previously untreated sites, and their reactions evaluated after a period of time.
5.1 In selecting a material for human contact in medical applications, it is important to ensure that the material will not stimulate the immune system to produce an allergic reaction under relevant exposure conditions. Extractable chemicals produced by skin contact or during physiological exposures may cause allergic reactions. Therefore, this practice provides for evaluations of solid or semisolid dosage forms using material extracts or direct evaluation of the test article. The rationale for this animal model is based on the fact that the guinea pig has been shown to be an appropriate animal model for predicting human contact dermatitis. Its tractable nature, its availability from reputable suppliers, the historical database of information already acquired using this species, and the correlation of such results to data on known human allergens, all contribute to its widespread use for allergenicity studies (1-5).4
5.2 The need for sensitization procedures other than the maximization test (Practice F720) is based on: (1) the need for a route of exposure more similar to use conditions; (2) concern over the use of adjuvant because of its recruitment of cell types to the test site which are not typically involved in immunologic reactions, and because of the discomfort this causes in the animals; (3) absence of a proper FCA-irritant control group in the traditional maximization design; and (4) the frequency of false positives often encountered with the GPMT. Both of these tests are internationally accepted (1).
1.1 This practice is intended to determine the potential for a substance, or material extract, to elicit contact dermal allergenicity.
1.2 This practice is intended as an alternative to the Guinea Pig Maximization Test (GPMT), given the limitations on dosage form and tendency for false positives associated with the latter test. See Rationale and References.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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