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Endpoint:
basic toxicokinetics in vivo
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
test procedure in accordance with generally accepted scientific standards and described in sufficient detail
Objective of study:
metabolism
Principles of method if other than guideline:
Method: other: not performed to guideline
GLP compliance:
yes
Specific details on test material used for the study:
1,2-benzisothiazol-3(2H)-one
Radiolabelling:
yes
Species:
rat
Route of administration:
oral: gavage
Duration and frequency of treatment / exposure:
96 hour(s)
Remarks:
Doses / Concentrations:
Males: 10 mg/kg - 20 mg/kg
No. of animals per sex per dose:
Males: 4-8
Details on study design:
Animals and dosing. Four male rats of the Alderley Park derived Wistrar strain (specific pathogen-free) were dosed orally with ([35S]BIT) (20 mg/kg; 0.81 µCi). Animals were transferred to individual metabolism cages for the separate collection of urine and faeces. Excreta were analysed daily for radioactivity. A group of eight male rats were given a solution of [35s]BIT (10 mg/kg, 0.76 µCi) orally. Two of the animals were killed 24 hours after dosing and portions of liver and abdominal fat removed for radiochemical analysis. The surviving animals were redosed and the procedure repeated at intervals of 24 hours until all the animals had been sacrificed.
Metabolites identified:
not measured
Rats given a single oral dose of BIT, labelled with sulphur-35, excreted 91% (range 82-96%) of the radioactivity in the urine and 5% (range 0.2-5%) in the faeces in five days. Neither BIT nor any of its metabolites are retained or accumulated in the liver or abdominal fat.
Conclusions:
An average of 91% of the radioactivity in the urine and 5% in the faeces in five days. Most (approximately 86%) of the material was excreted within 24 hours; there was some evidence, from individual animal variation, that BIT was absorbed at a variable rate from the gastro-intestinal tract.
There was no accumulation of BIT, or any of its metabolites in fat. The liver contained some radioactivity, but the amount corresponds to less than 0.2 ppm BIT.
Executive summary:

A study was conducted to study the excretion and distribution profile of the substance in rats. An average of 91% of the radioactivity in the urine and 5% in the faeces in five days. Most (approximately 86%) of the material was excreted within 24 hours; there was some evidence, from individual animal variation, that the substance was absorbed at a variable rate from the gastro-intestinal tract. There was no accumulation of the substance or any of its metabolites in the fat tissue. The liver retained traces of the absorbed substance (Conning, 1972).

Endpoint:
basic toxicokinetics in vivo
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
test procedure in accordance with generally accepted scientific standards and described in sufficient detail
Objective of study:
metabolism
Principles of method if other than guideline:
Method: conducted as per scientifically acceptable method
GLP compliance:
no
Specific details on test material used for the study:
Radiolabelled BIT
Radiolabelled with Sulphur-35
100% radiopurity [based on the statement that only a single radioactive component was detected when the compound was chromatographed on thin-layer plates of silica gel C in three solvent systems]
Radiolabelling:
yes
Species:
dog
Strain:
Beagle
Sex:
male
Route of administration:
oral: capsule
Vehicle:
other: corn oil
Duration and frequency of treatment / exposure:
24 hour(s)
Remarks:
Doses / Concentrations:
Males: One Beagle dog was given a gelatin capsule containing [35S]-BIT (1.2 mg/kg; 4.6 µCi) in corn oil.
No. of animals per sex per dose:
Males: 1
Control animals:
no
Conclusions:

Materials and methods
Ten male rats were dosed orally with [35S]-BIT (400 mg/kg; 0.23 µCi). The animals were housed collectively and the 24-hour combined urine sample was retained.
Two male rats were given an intraperitonea1 dose of [35S]-BIT alone (2.2 µCi). The animals were transferred to individual metabolism cages for the separate collection of urine.
One Beagle dog was given a gelatin capsule containing [35S]-BIT (1.2 mg/kg; 4.6 µCi) in corn oil. The animal was housed in an individual metabolism cage and was fed twice daily.
Radioactivity of all samples was determined. Pooled 24-hour urine from animals given [35S]-BIT was freeze-dried and triturated with ethyl acetate. The solution was filtered, evaporated under reduced pressure at 49°C and the residue dissolved in the minimum volume of water. The solution was adjusted to pH with saturated sodium bicarbonate and extracted with ethyl acetate. The solvent was evaporated and the residue dissolved in methanol.
Solutions of metabolites were applied to thin-layer plates of silica gel and developed one- or two- dimensionally.
Purified metabolites were characterised by co-chromatography with the available authentic compound and were analysed by mass spectrometry.

Results and discussion
Summarize relevant results; discuss dose-response relationship.
Two-dimensional chromatography showed that three metabolites were present, coded metabolites 1, 2 and 3.
Mass spectrometry of metabolite 2 showed the parent ion occurring at m/e 183.0355 which corresponds to C8H9NO2S. A peak also occurred at 168.0118 (M-CH3)+. This indicated that metabolite 2 was o-(methyl-sulphinyl)benzamide. When examined by mass spectrometry, metabolite 3 gave the parent ion at m/e 199.0301 (C8H9SO3N). This suggested that metabolite 3 was o-(methylsulphonyl) benzamide. The identity of metabolites 2 and 3 was confirmed by co-chromatography with the authentic compounds in solvent systems (D), (E), (G) and (H).
The identity of metabolite 1 was not determined, however the compound did not co-chromatograph with o-(methylthio)benzamide.
The relative distribution of metabolites in rat and dog urine is given in Table A6_2(2)-1. A metabolic pathway is postulated in Figure A6_2-1.
Chromatography in solvent systems (A)-(H) indicated that β-glucuronidase/ aryl sulphatase did not cause any hydrolysis.
Measurements of radioactivity indicated that a negligible amount of sulphate ion was present in the rat urine.

Conclusion
The routes of metabolism of BIT in the dog and rat are essentially similar. The breakdown of BIT by both species is rapid and is carried virtually to completion, since no unchanged BIT was found in either dog or rat urine. BIT does not appear to persist in the body since Conning (1972) found that neither BIT nor any of its metabolites are retained or accumulated in the liver or abdominal fat.
Williams (1959) has described the metabolic breakdown of disulphides, which may be considered to be similar to the compound under investigation. Disulphides are usually reduced in the body to mercaptans.
Williams also states that methylation of these SH compounds to yield sulphides which could then be oxidised to sulpones, is a possible further reaction.

This route is in agreement with that suggested by Palmer and Jones (1973) for the biodegradation of BIT in an aqueous system after the addition of an inoculum derived from raw settled sewage.
Executive summary:

A study was conducted to study the metabolism of the substance in rats and dogs. Ten male rats were dosed orally with radiolabelled test substance (400 mg/kg; 0.23 µCi). The animals were housed collectively and the 24-hour combined urine sample was retained. Two male rats were given an intraperitonea1 dose of the radiolabelled test substance alone (2.2 µCi). The animals were transferred to individual metabolism cages for the separate collection of urine. One Beagle dog was given a gelatin capsule containing 1.2 mg/kg bw of the radiolabelled test substance (4.6 µCi) in corn oil. The animal was housed in an individual metabolism cage and was fed twice daily. Radioactivity of all samples was determined. Pooled 24 hour urine from animals was freeze-dried and triturated with ethyl acetate. The solution was filtered, evaporated under reduced pressure at 49°C and the residue dissolved in the minimum volume of water. The solution was adjusted to pH with saturated sodium bicarbonate and extracted with ethyl acetate. The solvent was evaporated and the residue dissolved in methanol. Solutions of metabolites were applied to thin-layer plates of silica gel and developed one- or two- dimensionally. Purified metabolites were characterised by co-chromatography with the available reference substance and were analysed by mass spectrometry. Two-dimensional chromatography showed that three metabolites were present, coded metabolites 1, 2 and 3. Mass spectrometry of metabolite 2 showed the parent ion occurring at m/e 183.0355 which corresponds to C8H9NO2S. A peak also occurred at 168.0118 (M-CH3)+. This indicated that metabolite 2 was o-(methyl-sulphinyl)benzamide. When examined by mass spectrometry, metabolite 3 gave the parent ion at m/e 199.0301 (C8H9SO3N). This suggested that metabolite 3 was o-(methylsulphonyl) benzamide. The identity of metabolites 2 and 3 was confirmed by co-chromatography with the reference substances. The identity of metabolite 1 was not determined, however the compound did not co-chromatograph with o-(methylthio)benzamide. Measurements of radioactivity indicated that a negligible amount of sulphate ion was present in the rat urine. Based on the results of the studies, the routes of metabolism of the substance in the dog and rat are essentially similar. The breakdown of the substance by both species is rapid and is virtually complete, since no unchanged substance was found in either dog or rat urine (Dixon, 1976).

Endpoint:
basic toxicokinetics in vivo
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1999
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
test procedure in accordance with generally accepted scientific standards and described in sufficient detail
Objective of study:
absorption
Principles of method if other than guideline:
Method: conducted in accordance with scientifically accepted method
GLP compliance:
yes
Specific details on test material used for the study:
Test material
Nipacide BIT
Radiolabelled BIT

Lot/Batch number
Radiolabelled BIT: CFQ9246
Non-radiolabelled BIT: D909


Purity
Radiolabelled BIT: >98%
Non-radiolabelled BIT: 96.8%
Radiolabelling:
yes
Species:
rat
Strain:
Sprague-Dawley
Sex:
male
Route of administration:
other: oral (gavage) and dermal
Vehicle:
other: Proplyene glycol : Glycerol : Distilled water (45 : 30 : 25)
Details on exposure:
Oral dose (Group 1): 4, 8*, 24*, 48 and 72* hours (tissue distribution, *WBA also)
Dermal dose (Group 2): 4, 8*, 24*, 48 and 72* hours (tissue distribution, *WBA also)
Duration and frequency of treatment / exposure:
72 hour(s)
Remarks:
Doses / Concentrations:
Males: oral and dermal at dose level of 10 mg/kg body weight
No. of animals per sex per dose:
Males: 8 per group
Control animals:
no
Type:
excretion
Results:
96.6% of the dose absorbed following topical application and 99.5% of the dose absorbed following oral administration was excreted in 72 hours
Type:
absorption
Results:
96.6% of dose was absorbed orally
Type:
distribution
Results:
Less than 0.05% of the dose remained in any tissue at 48 hours after oral administration and topical application
Metabolites identified:
not measured
Conclusions:
Materials and methods
The absorption, distribution and excretion of radiolabelled material was determined at 4, 8, 24, 48 and 72 hours following a single oral administration or a single topical application of [14C]-Nipacide BIT (approximately 10 mg/kg; 5 MBq/kg). Any unabsorbed material was removed from the site by washing with 1% Tween 80 following the final collection.
Animals were sacrificed for quantitative whole body autoradiography at 8, 24 and 72 hours following both oral administration and topical application.

Results and discussion
The overall recoveries of radioactive material were 100 ± 2.0% for orally dosed animals and 106 ± 1.6% for topically dosed animals.
At 8 hours after a topical application, 3.2% of the radiochemical dose was absorbed and 23.9% remained in the treated skin and was, therefore, available for absorption.
At 72 hours after a topical application, 41.6% of the radiochemical dose was absorbed and 47.6% remained in the treated skin and was, therefore, available for absorption.
Radioactive material was rapidly and extensively absorbed through the skin and from the gastrointestinal tract. At 8 hours after an oral administration, 96.6% of the radiochemical dose was detected in samples other than the gastrointestinal tract. At 72 hours after a topical application, 41.6% of the radiochemical dose was absorbed and 47.6% remained in the treated skin and was, therefore, available for absorption.
The primary route of excretion was in the urine, with 96.6% of the activity absorbed following topical application and 99.5% of the radiochemical dose following oral administration, being excreted by this route in 72 hours.
Very little material was detected in the faeces, indicating that the majority of the radioactive material is absorbed following oral administration and that biliary excretion is unlikely to occur to any great extent (low levels of radioactive material were detected in the faeces and gastrointestinal tract (less than 0.5% of the radiochemical dose combined) following topical application).
The test material does not appear to be broken down to volatile components or excreted in the expired carbon dioxide, as indicated by high overall recoveries and low trap levels (less than 0.05% of the radiochemical dose) of radioactivity in trapping solutions.
Tissue disposition does not appear to occur. Less than 0.05% of the radiochemical dose remained in any tissue at 48 hours after oral administration and topical application, with the exception of the carcass and untreated skin following topical application which, combined, contained less than 1.5% of the radiochemical dose.

Conclusion
[14C]-Nipacide BIT is rapidly and extensively absorbed from the gastrointestinal tract and through the skin, and is then rapidly excreted, primarily in the urine, with little or no tissue disposition. Low levels of radioactivity were detected in the faeces, indicating that the majority of the radioactivity is absorbed following oral administration and that biliary excretion is unlikely to occur (low gastrointestinal tract and faeces levels following dermal application). The test material is not broken down into volatile components or expired as carbon dioxide.
Executive summary:

A study was conducted to study the absorption, distribution and excretion profile of the substance in Sprague-Dawley rats. The toxicokinetic profile was determined at 4, 8, 24, 48 and 72 hours following a single oral administration or a single topical application of the radiolabelled test substance at approximately 10 mg/kg bw (5 MBq/kg). Any unabsorbed material was removed from the site by washing with 1% Tween 80 following the final collection. Animals were sacrificed for quantitative whole body autoradiography at 8, 24 and 72 hours following both oral administration and topical application. The overall recoveries of radioactive material were 100 ± 2.0% for orally dosed animals and 106 ± 1.6% for topically dosed animals. At 8 hours after a topical application, 3.2% of the radiochemical dose was absorbed and 23.9% remained in the treated skin and was, therefore, available for absorption. At 72 hours after a topical application, 41.6% of the radiochemical dose was absorbed and 47.6% remained in the treated skin and was, therefore, available for absorption. Radioactive material was rapidly and extensively absorbed through the skin and from the gastrointestinal tract. At 8 hours after an oral administration, 96.6% of the radiochemical dose was detected in samples other than the gastrointestinal tract. At 72 hours after a topical application, 41.6% of the radiochemical dose was absorbed and 47.6% remained in the treated skin and was, therefore, available for absorption. The primary route of excretion was in the urine, with 96.6% of the activity absorbed following topical application and 99.5% of the radiochemical dose following oral administration, being excreted by this route in 72 hours. Very little material was detected in the faeces, indicating that the majority of the radioactive material is absorbed following oral administration and that biliary excretion is unlikely to occur to any great extent (low levels of radioactive material were detected in the faeces and gastrointestinal tract (less than 0.5% of the radiochemical dose combined) following topical application). The test substance does not appear to be broken down to volatile components or excreted in the expired carbon dioxide, as indicated by high overall recoveries and low trap levels (less than 0.05% of the radiochemical dose) of radioactivity in trapping solutions. Tissue disposition does not appear to occur. Less than 0.05% of the radiochemical dose remained in any tissue at 48 hours after oral administration and topical application, with the exception of the carcass and untreated skin following topical application which, combined, contained less than 1.5% of the radiochemical dose. Based on the study results, it can concluded that the substance is rapidly and extensively absorbed from the gastrointestinal tract and through the skin, and is then rapidly excreted, primarily in the urine, with little or no tissue disposition. Low levels of radioactivity were detected in the faeces, indicating that the majority of the radioactivity is absorbed following oral administration and that biliary excretion is unlikely to occur (low gastrointestinal tract and faeces levels following dermal application). The test substance is not broken down into volatile components or expired as carbon dioxide (O'Connor, 1999).

Description of key information

Key value for chemical safety assessment

Bioaccumulation potential:
no bioaccumulation potential
Absorption rate - oral (%):
100
Absorption rate - dermal (%):
100
Absorption rate - inhalation (%):
100

Additional information

A study was conducted to study the absorption, distribution and excretion profile of the substance in Sprague-Dawley rats. The toxicokinetic profile was determined at 4, 8, 24, 48 and 72 hours following a single oral administration or a single topical application of the radiolabelled test substance at approximately 10 mg/kg bw (5 MBq/kg). Any unabsorbed material was removed from the site by washing with 1% Tween 80 following the final collection. Animals were sacrificed for quantitative whole body autoradiography at 8, 24 and 72 hours following both oral administration and topical application. The overall recoveries of radioactive material were 100 ± 2.0% for orally dosed animals and 106 ± 1.6% for topically dosed animals. At 8 hours after a topical application, 3.2% of the radiochemical dose was absorbed and 23.9% remained in the treated skin and was, therefore, available for absorption. At 72 hours after a topical application, 41.6% of the radiochemical dose was absorbed and 47.6% remained in the treated skin and was, therefore, available for absorption. Radioactive material was rapidly and extensively absorbed through the skin and from the gastrointestinal tract. At 8 hours after an oral administration, 96.6% of the radiochemical dose was detected in samples other than the gastrointestinal tract. At 72 hours after a topical application, 41.6% of the radiochemical dose was absorbed and 47.6% remained in the treated skin and was, therefore, available for absorption. The primary route of excretion was in the urine, with 96.6% of the activity absorbed following topical application and 99.5% of the radiochemical dose following oral administration, being excreted by this route in 72 hours. Very little material was detected in the faeces, indicating that the majority of the radioactive material is absorbed following oral administration and that biliary excretion is unlikely to occur to any great extent (low levels of radioactive material were detected in the faeces and gastrointestinal tract (less than 0.5% of the radiochemical dose combined) following topical application). The test material does not appear to be broken down to volatile components or excreted in the expired carbon dioxide, as indicated by high overall recoveries and low trap levels (less than 0.05% of the radiochemical dose) of radioactivity in trapping solutions. Tissue disposition does not appear to occur. Less than 0.05% of the radiochemical dose remained in any tissue at 48 hours after oral administration and topical application, with the exception of the carcass and untreated skin following topical application which, combined, contained less than 1.5% of the radiochemical dose. Based on the study results, it can concluded that the substance is rapidly and extensively absorbed from the gastrointestinal tract and through the skin, and is then rapidly excreted, primarily in the urine, with little or no tissue disposition. Low levels of radioactivity were detected in the faeces, indicating that the majority of the radioactivity is absorbed following oral administration and that biliary excretion is unlikely to occur (low gastrointestinal tract and faeces levels following dermal application). The test material is not broken down into volatile components or expired as carbon dioxide (O'Connor, 1999).