4-amino-m-cresol

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Study period:

From March 1, 1985 to May 31, 1985

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study well documented, followed method comparable to guideline with deviation.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1986

Report date:

1986

Materials and methods

Objective of study:

absorption

distribution

excretion

Test guideline

Test guideline 1

Qualifier:

equivalent or similar to guideline

Guideline:

other: OECD Guideline 427 (Skin Absorption: In Vivo Method)

Deviations:

yes

Remarks:

Only 3 animals/sex/group were used instead of guideline recommendation of 4 animals/sex/group.

Test guideline 2

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 417 (Toxicokinetics)

Deviations:

yes

Remarks:

Only 3 animals/sex/group were used instead of guideline recommendation of 4 animals/sex/group

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

51956-65-1

Cas Number:

51956-65-1

IUPAC Name:

51956-65-1

Constituent 2

Reference substance name:

4-amino-3-methylphenol hemisulfate

IUPAC Name:

4-amino-3-methylphenol hemisulfate

Test material form:

not specified

Details on test material:

RADIOLABELED TEST MATERIAL
- Name of test material: [14C] 4-Amino-3-methyl Phenol hemisulfate
- Physical state: Solid
- Molecular weight: 172
- Substance type: Pure active substance
- Specific activity: 57 µCi/mg (9.8 mCi/mmol)
- Locations of the label: 14C-4-Amino-m-cresol hemisulphate (Ring-labelled)
- Stability under test conditions: Not reported
- Storage condition of test material: In the dark at -20°C

Radiolabelling:

yes

Remarks:

14C

Test animals

Species:

rat

Strain:

other: PVG

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Bantin & Kingman Ltd. (Grimson, Aldbrough, Hull)
- Age at arrival: 8-14 weeks
- Weight at arrival: 142-171 g
- Housing: Animals were housed up to 5 per cage according to sex in grid floor polypropylene cages. Soft white wood sawdust was used for the bedding.
- Individual metabolism cages: Yes
- Diet: Commercial pellet diet, SQC Rat and Mouse Maintenance Diet No. 1 Expanded (Special Diets Services, Stepfield, Witham, Essex, CM8 3AB), ad libitum
- Water: Tap water, ad libitum
- Acclimation period: Approximate 1 week

ENVIRONMENTAL CONDITIONS
- Temperature: 19 25°C
- Humidity: 34- 66%
- Air changes: Not reported
- Photoperiod: Natural lighting conditions supplemented by fluorescent lighting during working hours 8:45 to 17:00 hours

IN-LIFE DATES: From: March 1, 1985 To: May 31, 1985

Administration / exposure

Route of administration:

other: dermal (occluded)

Vehicle:

other: DMSO and commercial formulation with peroxide

Details on exposure:

PREPARATION OF DOSE SOLUTION/FORMULATION: Two dose formulations were prepared as follows:
a) Solution in DMSO: 14C radiolabelled test substance was dissolved in dimethyl sulphoxide (DMSO) to a concentration of 150 mg/mL.
b) Commercial formulation: The hair dye product containing the test substance was prepared as follows: “Akypo" (89.1 mg) suspended in distilled water (1.28 g) at 60°C, was added to a mixture of [14C]-4-amino-3-methyl phenol hemisulphate (134.4 mg), isopropyl alcohol (178 µL) and 25% ammonia (147.6 mg). The suspension was dissolved by heating at 60°C and Grundmasse A (2.83 g) was then added to the resultant solution. Equal weights of radiolabelled formulation and Welloxon were mixed to a smooth, even paste in a glass dish. Aliquots (1 g) of the mixture were then applied immediately to animals. The details on composition are provided in the study report.

TEST SITE
- Preparation of test site: Twenty four hours before dosing, an area on the dorsa-lumbar skin (ca 50 x 50 mm) of each animal was clipped free of hair using veterinary clippers.
- Area of exposure: 30 x 30 mm (9 cm2)
- % coverage: Not reported
- Type of wrap if used: For all animals, a strip of aluminum foil (approx. 45 x 45 mm) was covered with a piece of cotton gauze (45 x 45 mm) from which a center section (30 x 30 mm) had been removed (the gauze prevented any seepage of formulation outside the treated area). The cotton gauze was secured by encircling the the trunk of each animal with a strip of adhesive permeable plaster
- Time intervals for clippings: 24 hours before dosing

REMOVAL OF TEST SUBSTANCE
- Washing: After the contact period, the tape and occlusive pad were gently removed and the contact area was washed with shampoo and warm water before being dried with cotton wool swabs. An aluminum foil strip (approx. 45 x 45 mm) was placed over the treated area and secured. The dressing was left in place for the remainder of the study.
- Time after start of exposure: : 24 hours (test substance as solution in DMSO); 0.5 hours (test substance in commercial formulation)

TEST MATERIAL
- Amount(s) applied: : 0.1 mL (test substance as solution in DMSO); Commercial formulation 1 g (test substance in commercial formulation)
- Concentration: 150 mg/mL (test substance as solution in DMSO); 15 mg/g (test substance in commercial formulation)

VEHICLE
- Justification for use and choice of vehicle: Two different vehicles were evaluated
1. The hair dye formulation was chosen as the test substance to mimic actual end use.
2. The Dimethyl sulphoxide (DMSO) solution was chosen to serve as a standard condition to which the hair dye formulation results could be related.

USE OF RESTRAINERS FOR PREVENTING INGESTION: No, the dressing was tightened to stop the rat from wriggling free and give a good seal over the application site without causing undue stress to the animal.

Duration and frequency of treatment / exposure:

Single cutaneous application in DMSO (24 hour contact) and as part of a formulation with hydrogen peroxide (0.5 hour contact); total study period 72 hour

Doses / concentrations

Remarks:

Doses / Concentrations:
Test substance as solution in DMSO: 150 mg/mL, 0.1 mL/animal; 1.611 mg/cm2.
Test substance in commercial formulation: 1.5 %, 1 g/animal, 1.516 mg/cm2

No. of animals per sex per dose / concentration:

3 animals/sex/ group

Control animals:

no

Details on study design:

- Dose selection rationale: Not reported
- Rationale for animal assignment: Animals were assigned randomly

Details on dosing and sampling:

PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
- Tissues and body fluids sampled: Urine, feces, exhaled CO2, cage washes, blood, application site skin, gauze swabs/dressings, application site washings and tissues. The tissues collected were brain, liver, kidney, heart, muscle, spleen, bone (femur), gonads, fat (perirenal), gastrointestinal contents, skin (application site), eyes, lungs, adrenals, thyroid and residual carcass.
- Time and frequency of sampling: Urine, feces and exhaled CO2samples were collected at 24 hour intervals for 72 hours post-dosing. Blood samples were collected during exsanguination and tissues were collected after sacrifice of animals.

SACRIFICE: At 72 hour post treatment, the animals were exsanguinated under diethyl anesthesia.

COLLECTION AND STORAGE: Each metabolism cage was washed with methanol: water (1:1, v/v). All tissues were immediately weighed before storage at -20°C.

PROCESSING OF SAMPLES: Prior to radioactivity determination, the samples were processed as follows:
a) Gauze swabs and dressings: The occlusive pads and adhesive dressings removed after the initial contact periods (0.5 and 24 hour) and at the end of the study periods (72 hour) were extracted by refluxing in a 40% (w/v) methanolic potassium hydroxide solution for 5 hour. After cooling, the contents of the flask were filtered and the filtrate adjusted to 250 mL with methanol. The radioactive content of each solution was determined by liquid scintillation counting.
b) Application site washings: The cotton wool swabs used to cleanse the application site were filtered out from the aqueous washings and refluxed in methanolic potassium hydroxide solution as described above for ‘Gauze swabs and dressings’. After refluxing, the methanolic potassium hydroxide filtrate and the aqueous washings were assayed for radioactivity by liquid scintillation counting.
c) Application site: The entire dermal application site was removed after exsanguination at 72 hour post-dose. It was cut into sections approximately 1 cm2 and then refluxed in distilled water (ca 25 mL) and 40% (w/v) methanolic potassium hydroxide solution (65 mL) for 5 hour. After cooling, the contents of the flask were filtered and the filtrate adjusted to 250 mL with methanol. The radioactive content of each solution was then determined.
d) Biological samples: Volumes and weights of all biological samples were measured where appropriate. The residual carcasses were minced using a Hobart 1 h.p. meat mincer, a quantity of pellet diet being used to force the last of the carcass through the machine. Livers, minced carcasses (including diet) G.I.T. contents and faeces were homogenized in up to 4 volumes of distilled water using a Silverson Homogenizer (Silverson Machines Ltd., Waterside, Chesham, Bucks.). Ovaries, adrenal glands, thyroids and eyes were analyzed directly. All other tissues were thoroughly macerated using a pair of sharp scissors. Samples of whole blood, plasma, homogenates, processed and intact tissues were accurately weighed into Combusto-Cones™ (Packard Instrument Ltd.). These were allowed to dry at room temperature before being combusted in oxygen using a Packard Sample Oxidiser, Model 8306. The combustion products were absorbed in Carbo-sorb™ (8 mL), mixed with Permafluor V (15 mL) and the radioactivity determined by liquid scintillation counting.

DETERMINATION OF RADIOACTIVITY: Portions of urine, cage washings, plasma, dressing extracts and solubilized skin were added to scintillant (FisoFluor 1, 10 mL) and counted by liquid scintillation counting. Radioactivity was measured using a Packard Tri-carb Model 460CD Liquid Scintillation System (Packard Instruments Ltd., Caversham, Berks.) with facilities for computing quench-corrected disintegrations per minute (dpm). Efficiency correlation curves were routinely checked by the use of internal standards ({14C)-n- hexadecane, Amersham, International, Amersham, Bucks.) The spectrometer was recalibrated when a deviation between the counting efficiencies calculated from the quench indicating parameter (QIP) and the internal standards of greater than 3% was observed.

Results and discussion

Main ADME results

Main ADME results 1

Type:

absorption

Results:

Test substance was absorbed to a significant level (14.38%) if applied in DMSO: known skin-penetration enhancer, but to a lesser amount (2.73%) when applied in a commercial formulation.

Main ADME results 2

Type:

distribution

Results:

The organ distribution indicated very low levels for the organs investigated.

Main ADME results 3

Type:

excretion

Results:

Excretion is predominantly via the urine and to a minor extent via the faeces and lung. Excretion via urine is rapid, with 79.4 to 88.9 % being excreted within the first 24 hours.

Toxicokinetic / pharmacokinetic studies

Details on absorption:

- Accepting the mean amounts in urine, faeces, exhaled air, residual carcass, and as a worst case assumption the total content of the skin, as potential total bioavailable dose, a cutaneous absorption of 2.73% of applied dose equivalent to 41.4 µg/cm(2) was found for a commercial formulation applied under typical use conditions in the presence of peroxide. The respective amount for the DMSO solution is 14.38% of the applied dose equal to 231.7 µg/cm(2).

Details on distribution in tissues:

COMMERCIAL FORMULATION :
- In males, tissue concentrations of radioactivity at 72 hours post-dosing were either very low or below the limit of detection. The highest mean concentrations were found in the carcass (0.050 µg equivalents of [14-C] free base), blood and kidney (0.020 µg equivalents to [14-C] free base/g), lung, liver and the spleen (0.010 µg equivalents to [14-C] free base/g). Concentrations in other tissues were non-detectable. The highest mean quantities of radioactivity were found in gastrointestinal tract contents (0.120 equivalents to [14-C] free base, 0.001% dose) and residual carcass (6.040 equivalents to [14-C] free base, 0.063% dose).
- In females, tissue concentrations of radioactivity at 72 hours were similar to those found in male rats. The highest concentrations were found in the carcass (0.020 µg equivalents to [14-C] free base/g) and kidney (0.010 µg equivalents to [14-C] free base/g). Mean concentrations in other tissues were either below the limits of detection or less than 0.010 µg equivalents to [14-C] free base/g. The highest mean quantities of radioactivity were found in residual carcass (2.070 µg equivalents to [14-C] free base, 0.021% dose) and gastrointestinal tract contents and liver (0.020 µg equivalents to [14-C] free base, <0.001% dose). The mean total recovery of radioactivity from the tissues (including carcass) was 0.020% of the administered dose.
- Means of 2.80 and 1.73% of the applied radioactive dose were recovered from the treated areas of skin in male and female animals, respectively.
- The majority of the administered radioactivity was recovered from the dressings (mean males = 48.86%, mean females = 59.36%) and the application site washings (mean male = 34.47%, mean female = 28.34%).

TEST SUBSTANCE AS SOLUTION IN DMSO
- In males, radioactivity was detected in all tissues examined with the exception of the thyroid of all animals and adrenal of one animal. The highest mean concentrations were found in eyes (0.120 µg equiv./g), blood (0.080 µg equivalents to [14-C] free base/g), kidney (0.060 µg equivalents to [14-C] free base/g), carcass (0.050 µg equivalents to [14-C] free base/g) and spleen (0.040 µg equivalents to [14-C] free base/g). The highest mean quantities of radioactivity were found in residual carcass (6.22 µg equivalents to [14-C] free base, 0.063% dose) and gastrointestinal tract contents (0.56 µg equivalents to [14-C] free base, 0.006% dose).
- In females, radioactivity was found in all tissues examined with the exception of thyroid (rats 715 and 729 only), adrenal (rat 715 only) and gonads (animals 715 and 729 only). The levels were similar with the highest concentrations being found in eyes (0.080 µg equivalents to [14-C] free base/g), blood (0.060 µg equivalents to [14-C] free base/g) and adrenal (0.050 µg equivalents to [14-C] free base/g). The highest mean quantities were found in residual carcass (6.210 µg equivalents to [14-C] free base, 0.059%) and gastrointestinal tract contents (0.740 µg equivalents to [14-C] free base, 0.007% dose). The mean total recovery of radioactivity in the tissues (including carcass) represented 0.07% of the applied dose.
- Means of 7.86% and 6.10% of the applied radioactivity were recovered from the treated areas of skin of male and female rats, respectively.
- The majority of the applied radioactivity was recovered in the application site dressings (mean males = 74.38%, mean females = 81.60%). A significant proportion was also recovered from the application site washings (mean males = 4.41%, mean females = 4.12%).

Details on excretion:

COMMERCIAL FORMULATION GROUP:
- Means of 0.35 and 0.15% of the administered radioactivity were excreted in the urine of male and female animals, respectively (during the 72 hour period after dosing). Most of the radioactivity (mean males = 0.31%, mean females = 0.12%) was recovered in the 0-24 hour specimens.
- For fecal excretion, means of 0.02 and 0.01% of the administered radioactivity were recovered in the feces of male and female rats, respectively.
- Less than 0.2% of the administered radioactivity was recovered in the expired air traps for both male and female animals within 72 hours post-dosing.
TEST SUBSTANCE AS SOLUTION IN DMSO :
- Means of 8.09 and 5.00% of the administered radioactivity were excreted in the urine of male and female rats, respectively (during 72 hours post-dosing). The major portion of this radioactivity (mean males = 7.19%, mean females = 3.97%) was recovered in the 0-24 hour samples.
- Means of 0.27% and 0.58% of the radioactivity administered to male and female rats respectively were recovered in the feces during 72 hours post-dosing.
- Less than 0.20% of the radioactivity applied to either male or female rats was recovered in expired air traps during the 72-hour dosing.

Any other information on results incl. tables

- Throughout the duration of this study the animals showed no observable pharmacological or toxic effects which could have been attributed to the percutaneous administration of (14C) radiolabelled test substance.

RADIOACTIVE RECOVERY:

- In commercial formulation group, the mean total recoveries of radioactivity administered to male and female rats were 86.69 and 89.78%, respectively.

- In group treated with test substance as solution in DMSO, the mean total recoveries of radioactivity administered to male and female rats were 95.68 and 97.89%, respectively.

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information): low bioaccumulation potential based on study results
4-amino-m-cresol applied dermally to rats was absorbed to a significant level (14.38%) if applied in DMSO, a known skin-penetration enhancer, but to a lesser amount (2.73 %) when applied in a commercial formulation. Excretion was predominantly via the urine and to a minor extent via the faeces and lung Excretion via urine is rapid, with 79.4 to 88.9 % being excreted within the first 24 hours. Low tissue residue levels were noted when applied in DMSO solution or in a commercial formulation indicating, that bio-accumulation potential is low following dermal application. The organ distribution indicated very low levels for the organs investigated.
Based on a worse case assumption, that the total amount found in the rat skin will become bioavailable, a mean absorption rate of 41.4 μg/cm² was found for 4-Amino-m-cresol when applied in a commercial formulation in the presence of peroxide under typical use conditions.

Executive summary:

The absorption, distribution and excretion of 4-Amino-3-methyl Phenol hemisulfate after dermal application was determined by following the methods similar to the OECD guideline 427 (Skin absorption: In vivo Method) and 417 (Toxicokinetics).

14C radiolabelled test substance was dermally applied to groups of three male and three female pigmented strain PVG rats (body weight 142 - 171 g at arrival; 8- 14 weeks old). The application area was 9 cm² and the test substance was applied at concentrations of 15% in DMSO and of 1.5% in a commercial formulation with hydrogen peroxide (Hair dye product), for 24 h and 30 min contact, respectively. The mean dosages of the DMSO solution and commercial formulation were 1.611 mg/cm² and 1.516 mg/cm², respectively. During the exposure time the treated skin area was securely sealed by an occlusive plaster.

Thereafter, the test substance was scraped off (commercial formulation only) and the skin was rinsed with a shampoo formulation and warm water. After rinsing, the area was covered with an aluminium foil strip and securely sealed by an occlusive plaster to further prevent licking of the treated area during the 72 hour in the metabolism cages.

Urine and faeces were collected daily (0-24, 24-48 and 48-72 h after administration) from the metabolic cages. Exhaled carbon dioxide was removed every 24 hours for the 72 h post-dosing period.

Animals were killed 72 hours after the application and the application sites, blood and organs were taken and analyzed for radioactivity. The radioactivity in the remaining carcass was also determined.

Total recovery of the applied radioactivity was 86.7% and 89.8% for males and females treated with the commercial formulation, respectively. In the animals treated with DMSO solution, the total recovery for males and females was 95.7% and 97.9%, respectively.

The amount of radioactivity remaining at the application site (skin) for the commercial formulation represented 2.8% and 1.73% of the applied dose for males and females, respectively. The respective figures for the DMSO solution were 7.86 and 6.1 % for males and females.

Absorbed radioactivity was mainly excreted via urine both for the commercial formulation (0.35% males, 0.15 % females) and for the DMSO solution (8.09% males, 5.00 % females). Elimination was fast, with 79.4 - 88.9 % of the total amount being excreted within in the first 24 hours. Excretion via faeces was low for both the formulation (0.01 to 0.02 %) and the DMSO solution (0.27 to 0.58 %). Elimination via expiration was also relatively low at less than 0.2 % for both the commercial formulation and the DMSO solution. The majority of the applied doses was recovered in the dressings and the washing solutions, representing 83.3 to 87.7 % and 74.4 to 81.6 % of the applied amount for the formulation and the DMSO solution, respectively.

Low levels of radioactivity were detected in all tissues examined for the DMSO solution, except for the thyroid, adrenal and gonads, in which detectable amounts were only found in one sex and/or for some but not all of the animals within one group. The highest levels were noted for the remaining carcass (0.059 - 0.063 % of the applied dose) and the GI-tract content (0.006 - 0.007 % of the applied dose). The levels were generally low and the total residue in tissue minus the application sites, but inclusive of the carcass, represented 0.07 % of the applied dose for both sexes. In general, the tissue distribution did not reveal any sex differences. Similar findings were noted for the formulation, but the tissue levels were in general lower than the ones noted for the DMSO solution. Again, the highest levels were noted for the remaining carcass and the GI-tract content as observed with the DMSO solution. The figures obtained for males were almost identical to the ones noted with the DMSO solution, whereas for females lower residues were noted. The total residues in tissues (without application sites) and carcass in males and females represent about 0.07 % and 0.02 % of the applied dose, respectively. The higher residue was observed in the carcass of males. A similar tissue distribution was observed for males and females.

 

Accepting the mean amounts in urine, faeces, exhaled air, residual carcass, and as a worst case assumption the total content of the skin, as potential total bioavailable dose, a cutaneous absorption of 2.73 % of applied dose equivalent to 41.4 µg/cm² was found for a commercial formulation applied under typical use conditions in the presence of peroxide. The respective amount for the DMSO solution is 14.38 % of the applied dose equal to 231.7 µg/cm². No significant differences were noted between males and females with regard to skin absorption, tissue-distribution and elimination of 4-amino-m-cresol when applied with in either a hair dye formulation chassis or a DMSO solution.

4-Amino-3-methyl Phenol hemisulfate applied dermally to rats was absorbed to a significant level (14.38%) if applied in DMSO, a known skin-penetration enhancer, but to a lesser amount (2.73 %) when applied in a commercial formulation. Excretion was predominantly via the urine and to a minor extent via the faeces and lung excretion via urine is rapid, with 79.4 to 88.9 % being excreted within the first 24 hours. Low tissue residue levels were noted in both experiments, indicating, that bio-accumulation potential is low following dermal application. The organ distribution indicated very low levels for the organs investigated.

Based on a worse case assumption, that the total amount found in the rat skin will become bioavailable, a mean absorption rate of 41.4 μg/cm² was found for 4-Amino-3-methyl Phenol hemisulfate when applied in a commercial formulation in the presence of peroxide under typical use conditions.