1-[[2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolan-2-yl]methyl]-1H-1,2,4-triazole

Endpoint summary

Link to relevant study record(s)

Reference

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

April 1987 to February 1988

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)

GLP compliance:

yes

Radiolabelling:

yes

Species:

rat

Strain:

Sprague-Dawley

Remarks:

Crl:CD(SD)BR

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Age at study initiation: 6 to 10 weeks
- Weight at study initiation: 142 to 198 g
- Housing: prior to the study animals were housed up to five per cage according to sex in grid-floor polypropylene cages suspended over polypropylene trays containing soft white wood sawdust; during the study the animals were kept in individual all-glass metabolism cages suitable for the separate collection of urine, faeces and expired air
- Diet: commercial pellet diet ad libitum; fastin for 16 h prior to the administration of the test substance
- Water: ad libitum
- Acclimation period: 1 to 2 weeks

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 16 to 27
- Humidity (%): 52 to 82
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: April 1987 To: February 1988

Route of administration:

other: Gavage (Group B, C, D) and intraveneous (Group A)

Vehicle:

other: Gavage: ethanol:polyethylene glycol 200 : water (1 : 2 : 2, by volume). Intraveneous: physiological saline.

Duration and frequency of treatment / exposure:

Single dose or daily dose for 14 days

Dose / conc.:

0.5 mg/kg bw (total dose)

Remarks:

Group A - single, intravenous dose (radiolabelled test substance)

Dose / conc.:

0.5 mg/kg bw (total dose)

Remarks:

Group B - single, oral dose (radiolabelled test substance)

Dose / conc.:

0.5 mg/kg bw/day (nominal)

Remarks:

Group C - daily oral dose administration of non-radiolabelled test substance for 14 days followed by a one oral dose administration of radiolabelled test substance

Dose / conc.:

50 mg/kg bw (total dose)

Remarks:

Group D - single, oral dose (radiolabelled test substance)

No. of animals per sex per dose / concentration:

Minimun 5 animals per sex per dose

Control animals:

no

Positive control reference chemical:

None

Details on dosing and sampling:

TOXICOKINETIC / PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
- Tissues and body fluids sampled: urine, faeces, blood, tissues, cage washes, expired air
- Time and frequency of sampling:
Urine: 0-6, 6-12, 12-24, 24-48, 48-72, 72-96, 96-120, 120-144 and 144-168 h
Faeces: 0-6, 6-12, 12-24, 24-48, 48-72, 72-96, 96-120, 120-144 and 144-168 h
Expired air: 0-6, 6-12 and 12-24 h
- Tissues: bone, brain, fat (abdominal), heart, liver, skeletal muscle, residual carcass, adrenals, bone marrow, blood, gonads, kidney, lung, spleen, uterus

METABOLITE CHARACTERISATION STUDIES
- Tissues and body fluids sampled: urine, faeces
- Time and frequency of sampling:
Urine: 0-6, 6-12, 12-24, 24-48, 48-72, 72-96, 96-120, 120-144 and 144-168 h
Faeces: 0-6, 6-12, 12-24, 24-48, 48-72, 72-96, 96-120, 120-144 and 144-168 h
- From how many animals: pooled by sample type, sex and dose group
- Method type for identification: two-dimentional TLC; liquid scintillation counting
- Limits of detection and quantification: 1.5 times the background disintegration rate obtained from the measurement of pre-dose or blank samples of the same type

Statistics:

Mean values and standard derivation.

Details on absorption:

Renal elimination would suggest that at least 35 to 50% of the oral dose was absorbed. The similarity in the routes of elimination between the two routes of administration however, suggest an even higher level of oral absorption.

Details on distribution in tissues:

Following a single oral low dose the liver and kidney of most animals was found to contain radioactivity. Following 14 days pre-treatment with non-radiolabelled test article, the distribution of radioactivity was similar to that in non pre-treated animals. When given as a single i. v. dose, radioactivity was more widely distributed between tissues but levels were generally low.

Details on excretion:

The elimination of radioactivity following the administration of the test substance to the rat at dose levels of 0.5 and 50 mg/ kg was essentially complete by 48 hr post-dose. Following a single oral dose at both the low and high dose levels, radioactivity was voided approximately equally between urine and faeces. Pre-treatment with non-radiolabelled test substance or the administration of a single intravenous dose at the low level did not change this pattern of excretion. In all treatment groups, renal elimination was slightly greater in females than males.

Metabolites identified:

yes

Details on metabolites:

Regardless of route or dose level the test substance was extensively degraded with metabolism possibly proceeding through side chain oxidation giving the hydroxylated propyl derivative or replacement of the propyl group by a carboxylic acid. The metabolism may even result in the degradation of the dioxolane ring to a hydroxyl or carbomyl group.

 Table 1. Mean recovery of radioactivity from male and female rats following administration of radiolabelled test substance

	Percent of administered dose
	Group A 0.5 mg/kg iv		Group B 0.5 mg/kg po		Group C 0.5 mg/kg po*		Group D 50 mg/kg po
Urine	42.9	46.3	38.7	43.8	40.6	45.6	39.2	48.7
Faeces (extract)	19.4	19.0	25.0	18.8	19.8	18.1	24.4	20.5
Faeces (residue)	22.4	20.0	25.2	19.1	28.6	21.8	23.5	16.5
Cage washings	4.9	8.5	7.0	12.5	6.5	9.8	5.6	8.4
Cage debris	0.1	0.1	N.D.	N.D.	N.D.	N.D.	0.7	N.D
Expired air	N.D.	N.D.	N.D.	N.D.	N.D.	N.D.	N.D.	N.D.
Tissues	0.1	0.1	0.1	0.1	0.1	0.1	0.1	N.D.
Carcass	N.D.	N.D.	N.D.	N.D.	N.D.	1.0	N.D.	0.2

* after 14 daily doses of unlabelled material

N.D. = Not detected (< 0.1 % dose)

 

 

At the termination of the excretion studies, mean tissue concentrations of radioactivity were generally low or below the limits of detection:

 

Group A

The highest consistent mean quantity was present in liver (males 0.021 µg equiv/g (SD 0.005) = 0.11 % dose, females 0.010 µg equiv/g (SD 0.006) = 0.06 % dose). The quantity in bone marrow was 0.051 µg equiv/g (SD 0.046) in males and 0.008 µg equiv/g (SD 0.012) in females, in blood 0.001 µg equiv/g (SD 0.001) in males and 0.004 µg equiv/g (SD 0.010) in females.

 

Group B

The only tissues where radioactivity was consistently detected were liver (males 0.012 µg equiv/g (SD 0.009) = 0.07 % dose, females 0.007 µg equiv/g (SD 0.004) = 0.06 % dose) and kidneys (males 0.004 µg equiv/g (SD 0.002) = 0.01 % dose, females 0.004 µg equiv/g (SD 0.001) = 0.01 % dose).

No radioactivity was recovered in bone marrow and blood in males. The quantity in bone marrow was 0.006 µg equiv/g (SD 0.014) in females.

 

Group C

The highest mean quantity of radioactivity in males was present in liver (0.022 µg equiv/g (SD 0.004) = 0.11 %) and kidneys (0.006 µg equiv/g (SD 0.002) = 0.01 %). No radioactivity was recovered in bone marrow and blood in males. In females, low levels were detected in more tissues of most animals. The highest concentrations were present in liver (0.018 µg equiv/g (SD 0.004) = 0.11 %). The quantity in bone marrow was 0.036 µg equiv/g (SD 0.080) and in blood 0.002 µg equiv/g (SD 0.001) in females.

 

Group D

The highest mean levels of radioactivity were observed in liver (males 0.938 µg equiv/g (SD 0.297) = 0.06 % of dose, females 0.784 µg equiv/g (SD 0.415) = 0.04 % of dose) and in males in adrenals

(0.561 µg equiv/g (SD 0.773) = < 0.01 % of dose, in females in kidneys (0.366 µg equiv/g (SD ) = < 0.01 % of dose). No radioactivity was recovered in bone marrow in males. The quantity in bone marrow was 0.144 µg equiv/g (SD 0.322) in females. The quantity in blood was 0.076 µg equiv/g (SD 0.058) in males and 0.161 µg equiv/g (SD 0.199) in females.

 

Metabolites identified:

Examination of pooled urine and faecal extracts by two-dimensional TLC indicated the test substance is extensively metabolised, there being many radiolabelled breakdown products, particularly in faeces. The products varying between groups and sexes, particularly in high dose faecal extracts. There was, however, evidence of unchanged test substance in urine of animals dosed i.v. and in the faeces of animals treated orally. Between three and eight radiolabelled components were observed in urine. Following single low doses there was evidence for M9 and M2 (except i.v. dosed females ) as well as M3 and M10 (females only) in i.v. dosed animals. In pre-treated animals with the exception of M3, M2 and M10 in male urine most of the components did not correspond with the standards. Similarly in the high dose group, only in female samples was a component observed corresponding to a standard (M9 - 49.3%). Faecal extracts contained a very large number of components, most of which were very polar exhibiting very low Rf values in system 1. In animals given single low doses by either route components corresponding to M9 (except oral dosed females), and M1 were present. These products were also observed in pre-treated male animals, but not in females where most of the components were highly polar. At the high dose samples contained many more components (24 to 29) mostly polar, but there was evidence in the faeces of females of M9, M1 and M11 or M12.

Conclusions:

In this study performed in compliance with GLP and following a FIFRA 85-1 guideline administration of low doses of radiolabelled test substance to rats by the oral and intravenous routes resulted in similar patterns of elimination. Pre-treatment with non-radiolabelled test substance had no significant effect on the pattern of excretion or distribution of residual radioactivity. Administration of radiolabelled test substance at the high level resulted in a similar pattern of elimination with most of the dose being excreted by 48 hours. The concentrations of residual radioactivity in tissues were similar if not lower than those observed at the low dose level. Bioavailability (F) calculated is 90.7 %. This value is based on the excreted dose of 39 % in urine after oral administration and 43 % after intravenous administration in males at 0.5 mg/kg. (Bioavailability 39/43 = 90.7 %.) Regardless of route or dose level, radiolabelled test substance was extensively degraded with metabolism possibly proceeding through side chain oxidation giving the hydroxylated propyl derivative or replacement of the propyl group by a carboxylic acid. The metabolism may even result in the degradation of the dioxolane ring to a hydroxyl or carbonyl group.

Executive summary:

In this study performed in compliance with GLP and following a FIFRA 85-1 guideline, absorption, distribution, metabolism and elimination of radiolabelled test substance have been investigated following oral and intravenous administration to the Sprague Dawley rats of the Crl:CD(SD)BR strain. Studies were conducted using a low dose of 0.5 mg/kg and a high dose of 50 mg/kg (p.o). At the low oral dose level, studies were conducted with and without 14 consecutive days pre-treatment with nonradiolabelled test substance. Test substance was administered to four groups of rats, each comprising of at least five male and five female animals.

Administration of low doses of radiolabelled test substance to rats by the oral and intravenous routes resulted in similar patterns of elimination. Pre-treatment with non-radiolabelled test substance had no significant effect on the pattern of excretion or distribution of residual radioactivity. Administration of radiolabelled test substance at the high level resulted in a similar pattern of elimination with most of the dose being excreted by 48 hours. The concentrations of residual radioactivity in tissues were similar if not lower than those observed at the low dose level. Bioavailability (F) calculated is 90.7 %. This value is based on the excreted dose of 39 % in urine after oral administration and 43 % after intravenous administration in males at 0.5 mg/kg. (Bioavailability 39/43 = 90.7 %.) Regardless of route or dose level, radiolabelled test substance was extensively degraded with metabolism possibly proceeding through side chain oxidation giving the hydroxylated propyl derivative or replacement of the propyl group by a carboxylic acid. The metabolism may even result in the degradation of the dioxolane ring to a hydroxyl or carbonyl group.

Description of key information

- Oral absorption rate: 86% of applied dose with rapid absorption (Tcmax in blood = 1 hour), (Cresswell 1989, Bissig 1992)

- Distribution: Widely distributed (highest residues in liver, adrenals, kidney, ovaries, lungs), (Cresswell 1989, Bissig 1986, Hambock 1979, Bissig 1992)

- Bioaccumulation: No evidence of accumulation in organs and tissues (Bissig 1992)

- Excretion rate: 95% administered dose in 48 hours (65% bilary excretion), (Cresswell 1989, Bissig 1992)

- Extensive metabolism: No parent compound was found in urine of rats treated orally, faeces contained only about 3% of unchanged test substance, (Hambock 1979, Muecke 1979, Mucke 1983)

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Absorption rate - oral (%):

86

Absorption rate - dermal (%):

50

Absorption rate - inhalation (%):

100

Additional information

Absorption:

Orally administered test substance is rapidly absorbed from the intestinal tract in rodents (Cresswell 1989, Bissig 1992). The rate of absorption in rat was up to 86 % within 48 hours.

Three dermal absorption studies in rat indicated that up to 50 % or even more of the triazole labelled test substance may be dermally absorbed in rats within 24 hours but studies gave somewhat conflicting results about the rate of dermal absorption of the radiolabelled active substance (Ballantine 1986, Ballantine 1983, Murphy 1986). In two of the dermal studies, the absorbed dose of test substance was inversely related to the amount of test substance applied on the skin (Ballantine 1986, Murphy 1986).

 

Distribution:

The labelled active substance was widely distributed. Residue levels in tissues were fairly low in both rat and mouse, with the highest concentrations found in liver and kidneys (Cresswell 1989). Similar findings were reported in other studies whereby low levels of residual radioactivity was measured in various tissues and organs (Bissig 1986, Hambock 1979, Bissig 1992). 

 

Bioaccumulation:

No evidence of accumulation was observed. Following a single oral dose of 0.5 mg/kg to bile-duct cannulated male rats, the tissue residues at tcmax were below 0.05 ppm, except in liver, kidneys, lungs, plasma, and adrenals, and declined within 20 hours after administration below 0.02 ppm. The depletion kinetics was similar for all tissues. Based on the 4 data points (i.e. 1, 8, 14, and 20 hours after dosing) and assuming first order kinetics, the calculated half life times for the depuration for the residual radioactivity, was in the range of 6 to 10 hours (coefficient of correlation r2 = 0.84 to 0.95) (Bissig 1992). 

 

Excretion:

Excretion was rapid at both low (0.5 mg/kg bw) and high doses (50 mg/kg bw). In both cases around 95 % of the administered dose was excreted within 48 hours (Cresswell 1989). The active substance seems to be excreted in almost equal amounts in urine and faeces in both rats and mice, with only slightly higher excretion rates in urine by mice (Bissig 1986). No major differences were noted between orally and intravenously treated rats. The fairly high biliary excretion (65 % of the dose within 48 hours) indicates that a significant portion of the amount eliminated via faeces in rats is absorbed and re-entered into the intestinal tract (Bissig 1992).

 

Metabolism:

Test substance was eliminated mainly as metabolites in rat. No parent compound was found in urine (Hambock 1979, Muecke 1979). Faeces contained only about 3 % of unchanged test substance (doses around 30 mg/kg bw) (Mucke 1983). However, it was indicated in a study with bile-cannulated rats, that at a dose of 0.5 mg/kg bw the amount of unchanged test substance in faeces might be as high as 66 % of the administered dose (Bissig 1992). The metabolic reactions in rat included mainly oxidation and shortening of the n-propyl side chain, cleavage of the dioxolan ring and hydroxylation of the triazole and phenyl rings. Some evidence of cleavage of the alkyl bridge between the triazole and phenyl rings was also found. Metabolism study in mice indicated efficient cleavage of the dioxolan ring with subsequent conjugation reactions, especially in males. 

 

Dermal Absorption:

For the assessment of dermal absorption three in vivo studies are available. In the first study by Ballantine (1986), groups of four rats were exposed for 2, 4, 10, 24 and 82 hours at dose levels of 0.1, 1.0 and 10 mg/rat. The EFSA guidance on dermal absorption (2017) was used for assessing the data. The rate of absorption of 14C-test substance was inversely related to the dosage level (as the dosage level increases, the total percent absorbed decreases). Overall, a very wide range for dermal absorption values were observed. The low dose ranged from 25.17 - 64.61 %, with an average of 52.86 % and a standard deviation (SD) of 9.96. At the mid dose level, the dermal absorption ranged from 24.97 - 44.28 %, with an average of 33.64 % and SD of 6.30. And the dermal absorption at the high dose level ranged from 26.34 - 60.23 %, with an average of 34.20 % and a SD of 8.16. In the second study (Ballantine 1983), the recalculated dermal absorption value in the low dose group were 93.4 % and 91.5 % for male and female rats, respectively, and in the high dose group the values were 74.2 % and 98.3 % for male and female rats, respectively, at the 72 hours sampling time. In the third study (Murphy 1986), after a 10-hour exposure and 72-hour depletion phase (82-hour interval), the total percent absorbed (blood, carcass, skin, urine, faeces and cage wash) was 57.1 % and 42.9 % for the low and high dose levels, respectively, while the mid dose level at this time point did not show acceptable recovery levels for further assessment.

For a 24-hour exposure and 72-hour depletion phase (96-hour interval), the percentage absorbed was 65.8 %, 43.2 % and 76.7 % for the low, mid and high dose levels, respectively. With the exception of the second study were prolonged exposure was assessed, the dermal absorption values were wide-ranged and around 50 %, therefore the default value of 50 % was chosen for the dermal absorption.