Ethanol, 2-[(3-aminopyrazolo[1,5-a]pyridin-2-yl)oxy]-, hydrochloride (1:1)

Endpoint summary

Description of key information

In-vitro skin penetration (OECD 428):
- Penetration through Human Dematomed Skin (in-vitro): 0.068% after 24 hours
- Mean total systemically available dose: 0.106% of the applied dose

Key value for chemical safety assessment

Absorption rate - dermal (%):

0.106

Additional information

The test item was tested in an in vitro percutaneous penetration study through human dermatomed skin over 24 hours according to OECD TG guideline No. 428 (GLP, scored as validity 1 according to Klimisch criteria). The dose preparation (a typical oxidative hair dye formulation containing a nominal 4% test item which was mixed with peroxide developer (1:1 w/w)) was applied to the skin for 30 minutes to mimic in-use conditions. The mass balance and distribution of test item within the test system following the 24 hour run time was also determined.

The penetration process was monitored using [14C]-radiolabelled test item, which was incorporated into the formulation, prior to application. The receptor fluid was degassed phosphate buffered saline (PBS), in order to ensure that adequate sink conditions were maintained for this particular test material. The distribution of test item within the test system was measured and a 24 hour penetration profile was determined by collecting receptor fluid samples 0.5, 1, 2, 4, 8, 12, 16, 20 and 24 hours following application. The samples were analysed by liquid scintillation counting (LSC).

The results obtained in this study indicate that the test item at 2% in a typical oxidative hair dye formulation penetrated through human dermatomed skin at a very slow rate. The extent of test item penetration through human skin amounted to only 0.068% (0.272 ± 0.115 μg/cm2) of the applied dose, after 24 hours.

The mean total systemically available dose of test item (remaining epidermis plus dermis and receptor fluid) was 0.106% of the applied dose (corresponding to 0.422 μg/cm2).