Registration Dossier

Administrative data

Endpoint:
additional toxicological information
Type of information:
experimental study
Adequacy of study:
other information
Study period:
17.02.-19.03.2004
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2004
Report date:
2004

Materials and methods

Type of study / information:
Type: in vitro penetration through pig skin
Principles of method if other than guideline:
Draft OECD guidelines on in vitro percutaneous penetration (OECD 2003) / European Commission guidance document (2002) and ECETOC recommendations (1993)
GLP compliance:
yes

Test material

Constituent 1
Chemical structure
Reference substance name:
4-chlororesorcinol
EC Number:
202-462-0
EC Name:
4-chlororesorcinol
Cas Number:
95-88-5
Molecular formula:
C6H5ClO2
IUPAC Name:
4-chlorobenzene-1,3-diol
Test material form:
other:
Remarks:
beige powder
Details on test material:
Molecular weight: 144.65
Specific details on test material used for the study:
Unlabelled test material:
4-chlororesorcinol

Radiolabelled test material:
4-chlororesorcinol, [Ring-14C(U)]­
Radiochemical purity: 99.78%
Specific activity: 56.20mCi/mmol; 0.389mCi/mg
Molecular weight: 144.58

Results and discussion

Applicant's summary and conclusion

Conclusions:
1. The vast majority of the applied A 012 in the cream formulations was removed after a contact period of 0.5h by gently washing the skin with a mild detergent solution (99.5% from the formulation with hydrogen peroxide and 104% from the formulation without hydrogen peroxide). Less A 012 was washed offthe skin at 0.5h from the aqueous solution (62.9%) using the same procedure.

2. Less than 1 % of the A 012 applied remained in the stratum corneum at the end of the study from the cream application and approximately 6 - 10 times more was found in the stratum corneum following the aqueous application.

3. After washing and tape stripping, only 1.05% and 1.30% A 012 was found in the remaining epidermis/dermis from the applications with or without hydrogen peroxide, respectively and 6.63% from the aqueous application.

4. Only 0.448% and 0.651 % A 012 penetrated through the skin into the receptor fluid from the cream applications with or without hydrogen peroxide, respectively and 14.2% from the aqueous application at the end of the 48h sampling period.

5. The systemically available dose for the cream formulations with and without hydrogen peroxide and aqueous solution would be approximately 1.50%, 1.95% and 20.8%, respectively. Therefore, these calculated amounts could be used for risk assessments.

6. The results obtained in this study demonstrate that the penetration of A 012, from these formulations, through dermatomed pig skin is very slow when compared with the penetration rates of other penetrants measured using this in vitro technique with human skin (Dugard et al, 1984; Dugard and Scott, 1984).

7. These data demonstrate that the systemic availability, after dermal exposure to A 012 from two realistic formulations, would be low especially under normal use conditions in combination with a hydrogen peroxide developer and would be significantly less than that available from a solution of A 012 in water.
Executive summary:

1.1 Study design

The penetration of A 012 has been measured in vitro through dermatomed pig skin from a standard cream formulation (with and without hydrogen peroxide) and from a solution in water. The aqueous solution and formulated material, all containing a nominal 2.5% w/w A 012, were applied to the dermatomed membranes at a nominal rate of 10mg/cm2 and left unoccluded. The applications were rinsed off after a 0.5 h contact period, with the penetration of A 012 though the membrane being assessed throughout the entire 48h exposure period. At the end of the exposure period, the distribution of A 012 in the test system was assessed, which included a tape stripping technique to determine its distribution in the skin.

The applications and exposure conditions were designed to simulate potential human dermal exposure to the formulation during normal use and compare the penetration of A 012 from a standard formulation (with and without hydrogen peroxide) with the penetration from an aqueous solution.

Samples collected during this study were analysed by liquid scintillation counting (LSC).

1.2 Results

1.2.1 A 012 cream formulation with hydrogen peroxide

The dermal penetration of A 012 from the cream formulation with hydrogen peroxide through dermatomed pig skin was low and the vast majority ofthe <lose was recovered in the wash at 0.5h. Most of the penetration occurred during the first 4 hours giving a penetration rate of 0.110 µg/cm2/h, after which a small amount of A 012 penetrated, making the penetration rate over the 4 -48h sampling period 0.016µg/cm2/h and the overall rate (0 - 48h) 0.023µg/cm2/h. After the 0.5h exposure period, the amount which had penetrated was 0.062µg/cm2 (=0.024%) and after 48h, the amount penetrated was l. l7µg/cm2 (=0.448%). A small proportion of the dose was found adsorbed to the stratum corneum and absorbed in the remaining epidermis/dermis. The overall quantity found to be bioavailable (absorbed and penetrated) within 48 hours under the given study conditions was calculated to be 1.50% (= 3.91 µg/cm2) of the topically applied amount. The total recovery ofradioactivity from this application was 103%.

1.2.2 A 012 cream formulation without hydrogen peroxide

The dermal penetration of A 012 from the cream formulation without hydrogen peroxide was low and very similar to the application with hydrogen peroxide and again most of the dose was recovered in the washes. Most of the penetration occurred during the first 4 hours giving a penetration rate of 0.108µg/cm2/h, after which a small amount of A 012 penetrated, making the penetration rate over the 4 -48h sampling period 0.030µg/cm2/h and the overall rate

(0- 48h) 0.037µg/cm2/h. At 0.5h, the amount which had penetrated the membrane was 0.022µg/cm2 (=0.008%) and at 48h the amount penetrated was 1.69µg/cm2 (=0.651 %). A small proportion of the dose was found adsorbed to the stratum corneum and absorbed in the remaining epidermis/dermis. The overall quantity found to be bioavailable (absorbed and penetrated) within 48 hours under the given study conditions was calculated to be 1.95% (= 5.05µg/cm2) of the topically applied amount. The total recovery ofradioactivity from this application was 107%.

1.2.3 A 012 aqueous solution

The dermal penetration of A 012 from the aqueous solution was low but greater than from the cream formulations so a smaller proportion of the dose was recovered in the washes. Penetration occurred during the whole 48 hour test period giving a rate of 2.03µg/cm2/h during the first 4 hours (for comparison with the cream formulations) and the penetration rate between the 4 and 48h time period was 0.623µg/cm2/h. The overall rate (0-48h) was 0. 770µg/cm2/h. At 0.5h the amount which had penetrated the membrane was 0.111µg/cm2 (=0.044%) and at 48h the amount penetrated was 35.8µg/cm2 (=14.2%). A small proportion of the dose was found adsorbed to the stratum corneum and absorbed in the remaining epidermis/dermis. The overall quantity found to be bioavailable (absorbed and penetrated) within 48 hours under the given study conditions was calculated to be 20.8% (= 52.6µg/cm2) of the topically applied amount. The total recovery of radioactivity from this application was 105%.