3-iodo-2-propynyl butylcarbamate

Endpoint summary

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1995-03-01

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Objective of study:

absorption

distribution

excretion

metabolism

Qualifier:

according to guideline

Guideline:

EPA OPP 85-1 (Metabolism and Pharmacokinetics)

Deviations:

no

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 417 (Toxicokinetics)

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
Radiolabelled
- Source and lot/batch No.of test material: ZC9383

Unlabelled:
- Batch: 9312-7356

Radiolabelling:

yes

Species:

rat

Strain:

other: Crl:CDBR

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories
- Age at study initiation: 5 - 9 weeks
- Weight at arrival: Males: 182 - 297 g; females: 180 - 205 g
- Housing: individually
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: at least 7 days

ENVIRONMENTAL CONDITIONS
- Temperature: 19 - 25 °C
- Humidity: 50 +/- 20 %
- Photoperiod: 12 / 12 hrs dark / hrs light

Route of administration:

oral: gavage

Vehicle:

other: carboxymethylcellulose (CMC)

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
Radiolabeled dosing solutions were prepared by combining known amounts of radiolabeled test item, non-radiolabeled test item, and 0.5% (w/w) carboxymethylcellulose (CMC). The specific activity of the radiolabeled material was used to determine the mass of the 14C-test item in each dose. The amount of the non-radiolabeled test item and 0.5% CMC added to each dose and the total dose weight were measured gravimetrically. The components of the dose solutions were mixed at room temperature to ensure homogeneity. The 14C-dose solutions were prepared and verified for concentration and homogeneity either the day of or the day before dosing; they were stored in a refrigerator or at room temperature until use. The concentrations of the dosing solutions during dosing were determined by radioanalysis of pre- and post-dose aliquots of each solution. Results of the pre- and post-dose aliquot analyses were used to calculate the actual dose applied to each animal.

Duration and frequency of treatment / exposure:

Group A: single oral high dose (104 mg/kg bw actual received)
Group B: multiple oral low dose (14 daily doses of non labeled substance followed by a single radiolabeled dose on the 15th day; 20.4 mg/kg bw actual received)
Group C: single oral high dose (121 mg/kg bw actual received)
Group D: single oral low dose (19.1 mg/kg bw actual received)

Dose / conc.:

20 mg/kg bw/day (nominal)

Dose / conc.:

125 mg/kg bw/day (nominal)

No. of animals per sex per dose / concentration:

Group A and B: 5 animals/sex
Group C and D: 9 animals/sex

Control animals:

no

Positive control reference chemical:

not applicable

Details on study design:

- Dose selection rationale: based on data of other toxicity studies
- Rationale for animal assignment: random

Details on dosing and sampling:

TOXICOKINETIC / PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
- Tissues and body fluids sampled:
Group A and B: urine, faeces, exhaled air (every 24 h), blood and residual carcass (terminal sacrifice),
Group C and D: urine, faeces (after 2 and 4 h for the 2- and 4-hour sacrifice animals, every 24 h for the 5-day sacrifice animals), bone marrow, eyes, heart, liver, muscle, spleen, thyroid, bone, brain, fat, kidneys, lungs, ovaries, skin, testes, uterus, and residual carcass at sacrifice
- Time and frequency of sampling:

METABOLITE CHARACTERISATION STUDIES
- Tissues and body fluids sampled: see above
- Time and frequency of sampling: see above
- Method type for identification: Liquid scintillation counting

Type:

absorption

Results:

The test item is completely absorbed via the oral route

Type:

distribution

Results:

The test item was completely distributed over the bodies of either dose and sex

Type:

metabolism

Results:

The test item is exensively transformed in the rat

Type:

excretion

Results:

Major elemination route was in the urine in all groups and sexes

Metabolites identified:

yes

Details on metabolites:

The test item was extensively metabolised in the rat. It first underwent reductive dehalogenation to form PBC which is afterwards further metabolised by oxidative dealkylation. Major metabolites were the two stereo conformers of Propargyl-N-acetic acid carbamate and carbondioxide. Metabolites found in trace amounts included Methyl-N-butylcarbamate, 1-Hydroxybutamide and Propargyl-N-methylcarbamate. Several other trace metabolites could not be further characterised. Glucuronidation appeared to be the main secondary metabolism pathway.

Conclusions:

14C-labelled test item was administered orally to four groups of rats. Total mean recoveries for the individual dose groups (Groups A and B) were 106% and 96.1% for males and 98.1% to 81.9% for females, respectively. The majority of the radioactivity was recovered in urine (57.3% to 70.7%), a smaller amount (18.3% to 24.0%) was recovered in CO2, 4.40% to 7.44% in feces, and less than 3.1% recovered in carcass and tissues combined. Urine was the primary elimination route, and the majority of the radioactivity was eliminated within 48 Hours postdose. The percent of recovered radioactivity in the tissues (Groups C and D) declined with time through 120 hours postdose. All of the examined tissues for both male and female animals had less than 0.9% (excluding carcass) of the total administered radioactivity at 120 hours postdose. The concentration of radioactivity declined in the tissues with time through the final 120 hour postdose collection, although detectable amounts of radioactivity were found for both male and female animals in all matrices.
The test item is extensively biotransformed in the rat. The parent compound was not detected in the urine suggesting complete detoxification. Among several radioactive components detected in the urine, the major and the only significant metabolites were two distereomeric conformers of propargyl-N-acetic acid carbamate which accounted for 56% to 72% of urinary radioactivity and 32% to 51% of total radioactivity administered to the rat. Through the interpretation of its chemical and spectral characteristics, including the use of 2-D NMR, the structure of this metabolite was unambigously established. Metabolites found in the urine in trace quantities include methyl-N-butylcarbamate, 1-Hydroxybutamide and propargyl-N-methylcarbamate. The remaining metabolites were characterized by their chemical and enzymatic properties. Glucuronidation appeared to be the main secondary metabolism pathway; five metabolites were characterized as glucuronides.
Percent and concentration distribution of these metabolites in blood, liver, and kidney were determined. For all tissues examined propargyl-N-methylcarbamate and propargyl-N-acid carbamate gave the highest percent and concentration values in the samples collected at 2 and 4 hours postdose. At 120 hours these metabolites were not quantifiable but traces of a group of highly polar but uncharacterized metabolites were found in the tissues.
Among the dose regimens, there were no apparent sex-related differences regarding the absorption, distribution, elimination, or metabolism of 14C-labelled test item in rats.

Executive summary:

The absorption, distribution, elimination, and biotransformation of the test item were studied in male and female rats dosed orally with 14C-labelled test item. A total of 56 animals (28/sex) were placed on test. The test animals were divided into four groups. There were ten animals per group (5 male, 5 female) in Groups A and B which were used for mass balance and metabolite identification. Groups C and D had 18 animals per group (9 male, 9 female) and were used for tissue metabolite identification. Test material administration was as follows: single oral high dose (104 mg/kg, Group A), multiple oral low dose (14 daily nonradiolabeled doses followed by a single radiolabeled dose on the 15th day, 20.4 mg/kg, Group B), single oral high dose, (121 mg/kg, Group C), and single oral low dose (19.1 mg/kg, Group D).

Expired organic volatiles and carbon dioxide were collected from Groups A and B. All treated groups had urine and feces collected at prescribed intervals. Animals in Groups A and B were sacrificed 14 days after administration of the radiolabeled dose. Animals in Groups C and D (3/sex) were sacrificed at 2-, 4-, and 120-hours after administration of the radiolabeled dose. Selected tissue samples from Groups C and D were collected, weighed, and analyzed for total radioactivity. Blood, liver and kidney samples were analyzed for parent compound and metabolites.

Among the dose regimens, there were no apparent sex-related differences regarding the absorption, distribution, elimination, or metabolism of 14C-test item in rats.

Total mean recoveries for the individual dose groups (Groups A and B) were 106 % and 96.1 % for males and 98.1 % to 81.9 % for females, respectively. Of the total radioactivity, 57.3 % to 70.7 % was recovered in urine, 18.3 % to 24.0 in CO2, 4.40 % to 7.44 % in feces, and less than 3.1 % in the carcass. Urine was the primary elimination route and the majority of the radioactivity was eliminated within 48 hours postdose. The percent of recovered radioactivity in the tissues (Groups C and D) declined with time through 120 hours postdose. All of the examined tissues for both male and female animals had less than 0.9% (excluding carcass) of the total administered radioactivity at 120 hours postdose. The concentration of radioactivity declined in the tissues with time through the final 120 hour postdose collection, although detectable amounts of radioactivity were found for both male and female animals in all matrices.

The test item is extensively biotransformed in the rat. The parent compound was not detected in the urine suggesting complete detoxification. Among several radioactive components detected in the urine, the major and the only significant metabolites were two distereomeric conformers of propargyl-N-acetic acid carbamate which accounted for 56 %-72 % of urinary radioactivity and 32 %-51 % of total radioactivity administered to the rat. Metabolites found in the urine in trace quantities include methyl-N-butylcarbamate, 1 -Hydroxybutamide and propargyl-N-methylcarbamate. Other metabolites were characterized by their chemical and enzymatic properties. Glucuronidation appeared to be the main secondary metabolism pathway; five metabolites were characterized as glucuronides. Percent and concentration distribution of these metabolites in blood, liver and kidney were determined. For all tissues examined propargyl-N-methylcarbamate and propargyl -N-acid carbamate gave the highest percent and concentration values in the samples collected at 2 and 4 hours postdose. At 120 hours these metabolites were not quantifiable but traces of a group of highly polar but uncharacterized metabolites were found in the tissues.

Reference 2

Endpoint:

dermal absorption in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1995-03-27 to 1995-09-27

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

other: data requirement UK HSE Control of Pesticides Regulations

Version / remarks:

1986

Deviations:

yes

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 428 (Skin Absorption: In Vitro Method)

Deviations:

yes

Principles of method if other than guideline:

Deviations: The sampling time of the receptor fluid was 8 hours instead of 24 hours, as recommended. There is no information about the solubility of the test substance in the receptor fluid.

GLP compliance:

yes

Specific details on test material used for the study:

Three different comercially available formulations were investigated.
Formulation I containing 2.32 % w/w
Formulation II containing 0.604 and 0.583 % w/w
Formulation III containing 17.1 % w/w test item

SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: 31-83-a

RADIOLABELLING INFORMATION
- Radiochemical purity: 247 µCi (ca. 9 MBq)
- Specific activity: 962 MBq/mmol

Radiolabelling:

yes

Species:

other: human epidermis in vitro

Vehicle:

other: the test item was applied in each of three different commercially available formulations

Duration of exposure:

8 h

Doses:

- Applied volume: 50 µL

Details on in vitro test system (if applicable):

SKIN PREPARATION
- Source of skin: abdominal autopsy skin
- Type of skin: epidermal membranes
- Preparative technique: the full thickness skin sample was immersed in water heated to ca 60 °C for ca 1 minute. On removal, the epidermis was peeled away using forceps, floated on water and picked up onto aluminium foil. The membranes were then either used immediately, or stored wrapped in foil at ca 4°C overnight.
- Membrane integrity check: yes
- Storage conditions: at -20 °C or 4 °C overnight

PRINCIPLES OF ASSAY
- Diffusion cell: automated flow-through diffusion apparatus
- Receptor fluid: 0.9 % saline solution containing ca. 1 mg/mL tetracycline hydrochloride
- Solubility od test substance in receptor fluid:
- Flow-through system: yes
- Test temperature: 30-32 °C
- Reference substance: not applicable

Total recovery:

- Total recovery:
In samples treated with formulation I unabsorbed material accounted for 69-93% (mean 84%), with a further 1-17% associated with the solubilised skin sample itself. The radioactivity associated with the skin may be unabsorbed material not fully removed by die skin wash, or absorbed material within the membrane. Given the low cumulative absorption observed, the former explanation seems most likely. Radioactivity associated with die residual receptor contents was low (mean 0.13%).
As the proportion of the dose absorbed was greater for the formulation II the amount associated with unabsorbed material washed from the skin surface at 8 h was correspondingly lower than that observed for the Microtech formulation (48-69%, mean 60%). A small proportion of the applied dose was also recovered in the solubilised skin (2-4%). Again, diis may be either unabsorbed material not removed in the skin wash, or absorbed chemical within the membrane. The residual receptor fluid contents accounted for 1-2 % of the applied dose for this group of samples.
Unabsorbed material accounted for 93-100% (mean 97%) of the applied dose for die samples treated with formulation III reflecting the very low absorption observed in these samples. Correspondingly, the amount of material associated with die solubilised skin was lowest for this formulation (ca 1%), while the residual receptor contents amounted to a mean of only 0.04% of the applied dose.
- Limit of detection, LOD of LSC 30 dpm:

Key result

Time point:

8 h

Dose:

Formulation I

Parameter:

percentage

Absorption:

3.7 %

Key result

Time point:

8 h

Dose:

Formulation II

Parameter:

percentage

Absorption:

26.3 %

Key result

Time point:

8 h

Dose:

Formulation III

Parameter:

percentage

Absorption:

0.8 %

Table 1 In Vitro dermal Absorption

	Formulation I	Formulation II	Formulation III
Number of replicates	9	9	7
Applied radioactivity	3.75 to 3.94 mg/cm2	736 to 714 µg/cm2	32.81 to 33.12 mg/cm2
Test item concentration [%]	2.3	0.6	17.1
	[% applied dose]
Receptor fluid after 8 hours	3.66	26.25	0.80
Receptor rinse	0.13	1.29	0.04
Washings	83.85	59.71	96.79
Skin retention	6.49	3.20	0.77
Total recovery	94.12	90.45	98.40

Conclusions:

Following application of 14C-labelled test item to human epidermis in each of three different commercially available formulations the extent of absorption on a % dose basis was found to be formulation dependent. Cumulative absorption reached 3.66%, 26.25% and 0.80% for formulation I, II and III respectively. However, when the concentration in the different formulations was taken into account, the actual quantities of 14C-labelled test item absorbed were found to be similar for the three formulations. The corresponding absolute amounts of 14C-labelled test item absorbed were 140.49, 190.27 and 262.55 µg/cm^2 respectively. The data obtained suggest that absorption of 14C-labelled test item from these commercially available formulations is dependent on the capacity of the membrane for transport of the chemical rather than the amount of test item on the skin surface.

Executive summary:

14C-labelled test item was applied to human epidermis in vitro in each of three different commercially available formulations, and absorption measured over an 8 h period, equivalent to the likely duration of worker exposure to the chemical. Three different formulations were used in this study. Following application of 14C-labelled test item in formulation I, the cumulative absorption at 8 h reached 3.66 % of the applied dose, equivalent to 140.49 µg/cm^2. Proportional absorption was greater for formulation II, reaching 26.25 % at 8 h. However, due to the lower concentration of 14C-labelled test item in this formulation, this was equivalent to absorption of a similar total amount of test item (190.27 µg/cm^2). For the formulation III, the proportional absorption was lowest, reaching only 0.80 % of the applied dose in 8 h. This was equivalent to absorption of 262.55 µg/cm^2 over the 8 h period, as the concentration of test item in this formulation was greater than in the other formulations. The results indicate that absorption of 14C-labelled test item from the commercially available formulations is limited by the skin transport capacity for the chemical, rather than the quantity of chemical available for absorption.

Description of key information

Based on the data available, the test item is considered to be completely absorbed via the oral route, extensively transformed and mainly excreted via the urine.

Based on the results of an in vitro study, the test item is considered to be only poorly absorbed via the dermal route.

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Absorption rate - oral (%):

100

Additional information

Basic Toxicokinetics in vivo

14C-labelled test item was administered orally to four groups of rats. Total mean recoveries for the individual dose groups (Groups A and B) were 106 % and 96.1 % for males and 98.1 % to 81.9 % for females, respectively. The majority of the radioactivity was recovered in urine (57.3 % to 70.7 %), a smaller amount (18.3 % to 24.0 %) was recovered in CO2, 4.40 % to 7.44 % in feces, and less than 3.1 % recovered in carcass and tissues combined. Urine was the primary elimination route, and the majority of the radioactivity was eliminated within 48 Hours postdose. The percent of recovered radioactivity in the tissues (Groups C and D) declined with time through 120 hours postdose. All of the examined tissues for both male and female animals had less than 0.9 % (excluding carcass) of the total administered radioactivity at 120 hours postdose. The concentration of radioactivity declined in the tissues with time through the final 120 hour postdose collection, although detectable amounts of radioactivity were found for both male and female animals in all matrices.

The test item is extensively biotransformed in the rat. The parent compound was not detected in the urine suggesting complete detoxification. Among several radioactive components detected in the urine, the major and the only significant metabolites were two distereomeric conformers of propargyl-N-acetic acid carbamate which accounted for 56 % to 72 % of urinary radioactivity and 32 % to 51 % of total radioactivity administered to the rat. Through the interpretation of its chemical and spectral characteristics, including the use of 2-D NMR, the structure of this metabolite was unambigously established. Metabolites found in the urine in trace quantities include methyl-N-butylcarbamate, 1-Hydroxybutamide and propargyl-N-methylcarbamate. The remaining metabolites were characterized by their chemical and enzymatic properties. Glucuronidation appeared to be the main secondary metabolism pathway; five metabolites were characterized as glucuronides.

Percent and concentration distribution of these metabolites in blood, liver, and kidney were determined. For all tissues examined propargyl-N-methylcarbamate and propargyl-N-acid carbamate gave the highest percent and concentration values in the samples collected at 2 and 4 hours postdose. At 120 hours these metabolites were not quantifiable but traces of a group of highly polar but uncharacterized metabolites were found in the tissues.

Among the dose regimens, there were no apparent sex-related differences regarding the absorption, distribution, elimination, or metabolism of 14C-labelled test item in rats.

Dermal absorption in vitro

14C-labelled test item was applied to human epidermis in vitro in each of three different commercially available formulations, and absorption measured over an 8 h period, equivalent to the likely duration of worker exposure to the chemical. Three different formulations were used in this study. Following application of 14C-labelled test item in formulation I, the cumulative absorption at 8 h reached 3.66 % of the applied dose, equivalent to 140.49 µg/cm^2. Proportional absorption was greater for formulation II, reaching 26.25 % at 8 h. However, due to the lower concentration of 14C-labelled test item in this formulation, this was equivalent to absorption of a similar total amount of test item (190.27 µg/cm^2). For the formulation III, the proportional absorption was lowest, reaching only 0.80 % of the applied dose in 8 h. This was equivalent to absorption of 262.55 µg/cm^2 over the 8 h period, as the concentration of test item in this formulation was greater than in the other formulations. The results indicate that absorption of 14C-labelled test item from the commercially available formulations is limited by the skin transport capacity for the chemical, rather man the quantity of chemical available for absorption.