7a-ethyldihydro-1H,3H,5H-oxazolo[3,4-c]oxazole

Dermal absorption

Administrative data

Endpoint:

dermal absorption in vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2008

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: The study was conducted according to OECD guideline and in accordance with GLP

Cross-reference

Cross-reference 1

Reason / purpose for cross-reference:

reference to same study

Cross-reference 2

Reason / purpose for cross-reference:

reference to other study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2008

Report date:

2008

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 427 (Skin Absorption: In Vivo Method)

Deviations:

no

Remarks:

Not specified in the report

Principles of method if other than guideline:

Guideline followed

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

7a-ethyldihydro-1H,3H,5H-oxazolo[3,4-c]oxazole

EC Number:

231-810-4

EC Name:

7a-ethyldihydro-1H,3H,5H-oxazolo[3,4-c]oxazole

Cas Number:

7747-35-5

Molecular formula:

C7H13NO2

IUPAC Name:

7a-ethyl-tetrahydro-1H-[1,3]oxazolo[3,4-c][1,3]oxazole

Details on test material:

- Name of test material (as cited in study report): BIOBAN™ CS-1246, biocide
- Molecular formula (if other than submission substance): C7H13NO2
- Molecular weight (if other than submission substance): 143.09
- Physical state: Liquid, pale yellow
- Lot/batch No.: Non-radiolabeled: Lot # TC1031LAH3
Radiolabeled: Registry # DA2459
- Radiochemical purity (if radiolabelling): >98%
- Specific activity (if radiolabelling): Radiolabeled 20.92 mCi/mmol

Radiolabelling:

yes

Test animals

Species:

rat

Strain:

other: Crl:CD(SD)

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Jugular cannulated rats: Taconic (Germantown, New York)
Non-cannulated rats: Charles River (Portage, Michigan)
- Age at study initiation: 9-10 weeks
- Weight at study initiation: Males 234-337g and Females 167-211g
- Fasting period before study: ~16 hours
- Housing: Animals were housed singly in glass Roth-type metabolism cages
- Individual metabolism cages: yes
- Diet (e.g. ad libitum): Certified Rodent Diet, ad libitum
- Water (e.g. ad libitum): Municipal water, ad libitum
- Acclimation period: one week

ENVIRONMENTAL CONDITIONS
Temperature: 18.2 to 24.7°C
Humidity: 38-78%
Air Changes: 12-15 times/hour
Photoperiod: 12-hour light/dark (on at 6:00 a.m. and off at 6:00 p.m.)

Administration / exposure

Type of coverage:

semiocclusive

Vehicle:

polyethylene glycol

Duration of exposure:

The dermal dose site was washed six hours after application.

Doses:

Group 6 received a single dermal application of 14C-BIOBAN CS-1246.

Dermal Dose Preparation:
The dermal dose solution was prepared in PEG-400 at the target concentration of ~8.8 mg/g and applied at a dose volume of 10 µl/cm2 to 12 cm2 rat skin, which resulted in a dose of ~1 mg BIOBAN CS-1246 (120 µl of dose solution) to ~250 g rat resulting in the dose of 5 mg/kg. The dermal dose solution contained ~496 µCi/g radiolabeled BIOBAN CS-1246 and resulted in ~60-74 µCi per rat or ~295-333 µCi/kg.


HOMOGENEITY AND STABILITY OF TEST MATERIAL:
Following preparation of dose solutions (which include a mixing period of at least one day to produce a homogenous suspension), aliquots of each 14C-labeled solution were sampled from various locations within their containers and the radioactivity measured by LSS for homogeneity. Dose confirmation was determined by gas chromatography with flame ionization detection (GC-FID).

Dermal dose administration:
Animals were anesthetized with isoflurane for dosing. A measured dose of 14C-BIOBAN CS-1246 was applied topically using a round tipped feeding needle attached to an all-glass syringe to an approximately 12 cm2 area. The dose solution was applied evenly to the skin in a volume of 10 micro l/cm2. The syringe and feeding needle used for application of the test materials was weighed to determine the actual dose applied.

No. of animals per group:

4 rats per sex per dose level will be used in this study; except, a probe study consisting of one or more animals may be conducted in order optimize the experimental design of the actual study.

Control animals:

yes

Details on study design:

A measured dose of 14C-BIOBAN CS-1246 will be applied topically using a round tipped feeding needle attached to an all-glass syringe to an approximately 12 cm2 area. The dose solution will be applied evenly to the skin in a volume of 10 l/cm2. The syringe and feeding needle used for application of the test materials will be weighed to determine the actual dose applied.

Dermal Wash
Animals dosed dermally will be anesthetized with isoflurane six hours post-dosing. The macroporous filter material covering will be removed and the skin at the dose site washed 5 times with cotton tip applicators dipped in an aqueous solution of detergent (i.e., ~2-4% Ivory dish washing liquid, Proctor and Gamble Co., Cincinnati, Ohio). The dose site will also be rinsed several times with gauze soaked with water and the area blotted dry with gauze squares. Following washing, the Teflon Spectra/Mesh covering will be replaced and the rats returned to their cages for the continuous collection of time-course blood, urine, feces, and terminal collection of tissues. Radioactivity will be determined in the Teflon Spectra/Mesh coverings, the cotton tips and gauze to determine the dose which remained at the site six hours after the application.

Volatiles from Dermal Application Site
If the test material is found to be evaporating from the vehicle, charcoal traps will be used to trap the volatile test materials from the site until the site has been washed.

Urine
All urine voided during the study will be collected in dry-ice cooled traps. The urine traps will be changed at 12 and 24 hours post-dosing followed by 24-hour intervals for the remainder of the study. The cages will be rinsed with water at the time the traps are changed and the rinse collected. Each urine specimen and urine/cage rinse will be weighed, and a weighed aliquot of each sample analyzed for radioactivity by LSS as described below. Equal volume aliquots of urine samples from the 0-12 hour and 12-24 hour collection intervals will be pooled and stored at 80ºC for chemical analysis.

Feces
Feces will be collected in dry-ice chilled containers at 24-hour intervals. An aqueous homogenate (~ 25% w/w) will be prepared and weighed aliquots of these homogenates oxidized and quantitated for radioactivity by LSS. In addition, equal volume aliquots of fecal homogenates from each animal will be taken from the 0-24 hour collection interval and pooled. These pooled samples will be stored at -80ºC for possible chemical analysis.

Expired Volatiles
Air will be drawn through the cages at approximately 500 ml/minute. Upon exiting each cage, the air will be passed through charcoal to trap organic volatiles. The charcoal traps will be changed at 24 hours. Radioactivity trapped on the charcoal will be desorbed with weighed amounts of toluene. Weighed aliquots of the toluene will be analyzed for radioactivity. If less than 1% of the administered dose is detected in the charcoal trap of the first orally dosed group during the first 24 hours of trapping, the replacement traps will not be analyzed for radioactivity and air will not be trapped for any other groups.

For animals that will be exposed dermally to the test material (Group 6), a probe study will be conducted to determine the volatility of the dermally applied BIOBAN CS-1246 during the exposure.

Expired CO2
Following the charcoal trap (described above) the expired air will be passed through a solution of monoethanolamine:1-methoxy-2-propanol (3:7 v/v) to trap expired CO2 and analyzed for radioactivity. The CO2 trap is originally scheduled to be changed at 12-hour intervals through 48 hours, followed by 24-hour intervals for the remainder of the study. However, <1% of the administered dose is detected in the CO2 trap in the first orally dosed group during the first 12 hour interval, CO2 traps will not be used in the remainder of the study.
At the specified time (?95% of the administered radioactivity is recovered in urine, feces for all other groups), animals will be anaesthetized with CO2/O2 and sacrificed by exsanguination.

Dermal Application Devices
At the time of sacrifice, the site will be washed again as described above and the Teflon frames, second Teflon Spectra/Mesh coverings, and the dermal jackets will be collected separately to determine the remaining radioactivity.

Tape Stripping of the Dermal Application Site
The dermal application site will be tape stripped (10-15 times) in order to collect stratum corneum and determine radioactivity associated with it. Tape stripping will be conducted using D-SQUAME skin surface sampling adhesive discs.

Tissues
The carcass, brain, GI tract with contents, liver, kidney, spleen, and testes will be homogenized (~33% homogenate) and a weighed aliquot oxidized using a sample oxidizer and analyzed for radioactivity by LSS. Blood (heparinized or non heparinized) will be centrifuged to obtain plasma and RBCs, plasma will be directly analyzed for radioactivity by LSS, whereas RBCs will be oxidized before LSS. The skin will be removed from the carcass and a representative skin sample will be oxidized and analyzed for radioactivity by LSS. The remaining tissues will be directly oxidized without homogenization and analyzed for radioactivity by LSS.

Final Cage Wash
Following the terminal sacrifice of the animals, a final cage wash will be performed. The final cage wash will be collected and the weight of the sample is determined. A weighed aliquot of the final cage wash will be analyzed for radioactivity.

ANALYSES
Following preparation of dose solutions (which included a mixing period of at least one day to produce a homogenous suspension), aliquots of each 14C-labeled solution will be sampled from various locations within their containers and the radioactivity measured by LSS for homogeneity. Confirmation of the test material concentration in the dose solutions will be conducted..
The whole tissue (small tissues) or a weighed aliquot of the tissue (e.g., liver, GI tract with contents, carcass) samples (homogenates) will be oxidized using a sample oxidizer and analyzed for radioactivity by LSS as described below.
Radioactivity will be quantified in a liquid scintillation spectrometer. Counts per minute (cpm) will be corrected for quench and background, and converted to disintegrations per minute (dpm). Performance of the LSS is monitored once every 23 hours while in use, as per the lab SOP. Samples collected from Group 6 animals will be counted for longer period of time (i.e., 2 hours/sample) once they normally become below twice the background levels in order to confirm that extremely low levels of the applied radioactivity is not moving into blood stream from the deeper layers of skin. Pooled urine samples from selected urine samples will undergo chemical analysis. Pooled feces samples from selected intervals may undergo chemical analysis. Selected plasma samples may undergo chemical analysis.

Details on in vitro test system (if applicable):

None

Results and discussion

Signs and symptoms of toxicity:

no effects

Dermal irritation:

no effects

Absorption in different matrices:

Absorption of the dermal dose was determined from the percent of administered radioactivity recovered in urine and rinse, final cage wash, CO2, tissues, and feces. A mean total of 27±3% and 25±5% of the dermally applied dose of 5 mg BIOBAN™ CS- 1246/kg (Group 6) was systemically absorbed to male and female rats, respectively (Table 3). The unabsorbed radioactivity of 43±6% (males) and 41±4% (females) was recovered from the skin wash, covering, tape strips, frame and dosed skin.

Total recovery:

A much lower percent of the administered radioactivity was recovered in the urine of the dermally dosed (Group 6) rats. Over the 168-hour collection period, 19% and 15% of administered dose was recovered in urine of males and females, respectively. Furthermore, the appearance of radioactivity in urine was slower than that observed for the oral dose groups, with only 9-11% of the administered dose excreted within the first 24 hour (accounting for 46-65% of the total radioactivity excreted over the entire collection period). Total urinary elimination accounted for 64-80% of the absorbed dose during the course of the study. Slow and low urinary elimination was consistent with pattern of slow penetration of the applied dose from the dermal site of application and limited absorption of the applied dose, as expected due to cornified layer of cells on the skin surface that workas a barrier slowing skin penetration of xenobiotics.

The 14C-BIOBAN™ CS-1246-derived radioactivity recovered in feces of the dermal group (Group 6) was only 4%.

As expected on the basis of low absorption via the dermal route of exposure, a lower percentage of administered radioactivity was associated with tissues of animalsreceiving a single dermal dose of 14C-BIOBAN™ CS-1246. On average, only 3% of the dermally administered radioactivity remained in tissues at terminal sacrifice (168 hours post-dosing). Most (2.6-2.7%) was recovered in the skin remote from the application site and 0.8-1.7% was recovered from skin at the site of application. Tissue residue concentrations from the dermally dosed animals were similar to those observed in tissues of orally dosed animals of Group 1. For males, the highest concentrations of radioactivity was found in skin (0.698 μg/g) > liver (0.066 μg/g) > thyroid (0.033 μg/g) ≥ kidney (0.029 μg/g); for females, the order was skin (0.762 μg/g) > carcass (0.015 μg/g) >kidney (0.009 μg/g) = stomach tissue (0.009 μg/g). The difference in the residual radioactivity between the dose-site skin (4.2 μg/g [male] and 2.1 μg/g [female]) and skin at remote from the dosed site (0.7 μg/g [male; 3 out of 4 values between 2.3 and 3.6 μg/g] and 0.8 μg/g [female]) was only 6-fold (male; two out of four was between 3- and 4-fold) and 3-fold (female). Such a low difference in the residual radioactivity between the dosed site skin and skin at other sites of the body was an indication that complete absorption has been achieved and any additional penetration of radioactivity from the application site was not likely to occur.
For most dose groups, fat and fatty tissue (e.g., brain) generally exhibited the lowest accumulation of 14C-BIOBAN™ CS-1246-derived residues.

Conversion factor human vs. animal skin:

No data

Any other information on results incl. tables

Refer below attachments:

Attachment 1. Text Table.1 Study Design

Attachment 2: BIOBAN™ CS-1246 BIOCIDE: PHARMACOKINETICS AND METABOLISM IN CRL:CD(SD) RATS

Applicant's summary and conclusion

Conclusions:

BIOBAN™ CS-1246 was rapidly absorbed, completely metabolized and readily eliminated from the rat Within 144-168 hours after dosing, animals were almost free of radioactivity (1-3% total in the body). These data that accumulation of BIOBAN™ CS-1246 would not occur upon exposure.

Executive summary:

The purpose of this study was to provide data on the absorption, distribution, metabolism, and elimination (ADME) of BIOBAN™ CS-1246 biocide hereafter referred to as BIOBAN™ CS-1246 following oral gavage or dermal administration to rats in support of registration (OPPTS Guideline 870.7485, OECD Guideline 417 & 427, EC, Guideline B.36). This study was conducted to determine absorption, distribution, metabolism, and excretion of 14C-BIOBAN™ CS-1246 following dermal exposure to groups (n =4) of male and female Crl:CD(SD) rats. Dermal absorption of BIOBAN™ CS-1246 was slow. Recovery of the dermally applied dose was 66-70%, due to volatilization of the test material and/or degradates.

Elimination of the dermally applied dose was low accounting for only 17-20% of the applied dose, most (9-11%, 37-41% of the absorbed dose) within 24 hours of dosing. Total fecal elimination of the dermal dose was only 4% (15-16% of the absorbed dose).

An average of 3% of the dermally dosed 14C-BIOBAN™ CS-1246 remained in the tissues of the animals sacrificed 168 hours post-dosing, most (2.6-2.7%) was found in skin remote from the application site and only 0.8-1.7% was recovered from the application site skin. Such a low difference in the residual radioactivity between the dosed site skin and skin at other sites of the body was an indication that complete absorption has been achieved and any additional penetration of radioactivity from the application site was not likely to occur.

The peak plasma concentration of 14C-BIOBAN™ CS-1246 among the dermally dosed rats occurred 2-3 hours post-application. The plasma Cmax of radioactivity after dermal administration was 32- to 41-fold lower than after oral dosing. The rate of dermal absorption was 0.14-0.20 h-1 and the t½ of elimination of absorbed radioactivity was 0.14- 0.20 hours. The plasma AUC was 7-8 fold lower after dermal than oral dosing. The

clearance was 9-10 fold higher after dermal dosing consistent with 7- to 8-fold lower plasma AUC and rapid elimination of the absorbed radioactivity.

Test-material derived radioactivity was also present in RBC, with Cmax concentrations ~75% of the levels seen in plasma. The time-course radioactivity in RBC roughly paralleled the plasma time-course concentration profiles at much lower concentrations. Kinetics (absorption, elimination t½, AUC, clearance) of radioactivity from RBC were slower than plasma as detectable levels of radioactivity were found in RBC for extended period of time when compared to plasma.

The absorbed test material was completely metabolized, affording 2-amino-2-ethyl-1,3- propanediol (AEPD) as the only metabolite above 5% of the administered dose in all urine and fecal samples analyzed from all dose groups. Four minor metabolites were also observed above 0.5% of the administered dose, but not identified.

In summary, administered BIOBAN™ CS-1246 was rapidly absorbed, completely metabolized and readily eliminated from the rat Within 144-168 hours after dosing, animals were almost free of radioactivity (1-3% total in the body). These data that accumulation of BIOBAN™ CS-1246 would not occur upon exposure.