Sodium 1-(3,4-dihydro-6-methyl-2,4-dioxo-2H-pyran-3-ylidene)ethanolate

Endpoint summary

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

Circa 1950

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:

absorption

toxicokinetics

Qualifier:

no guideline available

Principles of method if other than guideline:

Basic toxicokinetic study

GLP compliance:

no

Specific details on test material used for the study:

Dehydroacetic acid DHA, CAS 520-45-6

Radiolabelling:

no

Species:

monkey

Strain:

not specified

Details on species / strain selection:

not specified

Sex:

not specified

Details on test animals or test system and environmental conditions:

not specified

Route of administration:

oral: gavage

Vehicle:

olive oil

Duration and frequency of treatment / exposure:

5 days/week for 290-397 days

Dose / conc.:

50 mg/kg bw/day (nominal)

Dose / conc.:

100 mg/kg bw/day (nominal)

Dose / conc.:

200 mg/kg bw/day (nominal)

No. of animals per sex per dose / concentration:

1

Control animals:

not specified

Details on dosing and sampling:

not specified

Statistics:

not specified

Type:

absorption

Results:

Peak concentration occurred at 4.5 and 7 days after dosing.

Details on absorption:

Peak concentration occurred at 4.5 and 7 days after dosing. Plasma levels were 15, 26 to 33, and 45
to 51 mg/100 ml from lowest to highest dosage and diminished rapidly and progressively from high- to
low-dose groups.

Details on distribution in tissues:

not specified

Details on excretion:

not specified precisely

Metabolites identified:

not specified

Bioaccessibility (or Bioavailability) testing results:

not specified

Conclusions:

Peak concentration occurred at 4.5 and 7 days after dosing. Plasma levels were 15, 26 to 33, and 45
to 51 mg/100 ml from lowest to highest dosage.
Olive oil had no apparent effect on absorption.

Executive summary:

Monkeys (2 per dose group) received oral doses of 50, 100, and 200 mg/kg bw/day, 5 days per week,

for 290 to 397 days. Dehydroacetic Acid was administered in olive oil to 1 monkey in each group.

Plasma concentrations of Dehydroacetic Acid were determined at various intervals after dosing. The

peak concentration occurred between 4.5 and 7 hours after dosing (plasma levels at 4 hours from low

dose to high were 15, 26 to 33, and 45 to 51 mg/l00 ml, respectively), and diminished rapidly and

progressively from high- to low-dose groups. Olive oil apparently had no influence on absorption.

Reference 2

Endpoint:

basic toxicokinetics in vivo

Type of information:

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

Adequacy of study:

weight of evidence

Justification for type of information:

refer to analogue justification provided in IUCLID section 13

Reason / purpose for cross-reference:

read-across source

Type:

absorption

Results:

Peak concentration occurred at 4.5 and 7 days after dosing.

Reference 3

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

Circa 1950

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Objective of study:

absorption

toxicokinetics

Qualifier:

no guideline available

Principles of method if other than guideline:

Basic toxicokinetic study

GLP compliance:

no

Radiolabelling:

no

Species:

dog

Strain:

not specified

Sex:

not specified

Route of administration:

other: oral and intravenous

Vehicle:

not specified

Duration and frequency of treatment / exposure:

Sodium Dehydroacetate was administered in a single dose of 160 mg/kg (Dehydroacetic Acid) to each of 4 dogs-2 orally, 2 intravenously. And single intravenous doses of 20 to 480 mg/kg Dehydroacetic Acid (as Sodium Dehydroacetate) were given to 6 dogs.

Dose / conc.:

20 mg/kg bw/day (nominal)

Remarks:

intermediate doses are assummed from the authors description but not precisely specified.

No. of animals per sex per dose / concentration:

1-6

Control animals:

not specified

Positive control reference chemical:

Not specified.

Details on dosing and sampling:

Not precisely specified.

Statistics:

Not specified.

Type:

absorption

Results:

See below

Details on absorption:

The collection and analysis of blood samples revealed rapid absorption, with maximum plasma
concentrations (approximately 22 to 26 mg/l00 ml) occurring 1.5 to 2 hours after administration and
diminishing slowly thereafter; traces of Dehydroacetic Acid
remained after 3 to 4 days. This slow elimination of Dehydroacetic Acid in the dog was supported by
another experiment in which single intravenous doses of 20 to 480 mg/kg Dehydroacetic Acid (as
Sodium Dehydroacetate) were given to 6 dogs. Similar results were obtained; Dehydroacetic Acid
was detectable after 3 days at doses of 80 mg/kg and above.

Details on distribution in tissues:

Not specified.

Details on excretion:

Not specified.

Metabolites identified:

not specified

Bioaccessibility (or Bioavailability) testing results:

Not specified.

Conclusions:

TK analysis in the dog revealed that peak concentrations of DHA-Na were at 1.5 to 2 hours after dosi
ng (approx. 22 to 26 mg/100ml) and that traces of DHA-Na remained after 3 to 4 days at 80 mg/kg
and above.

Executive summary:

In a basic TK study DHA-Na was administered in a single dose of 160 mg/kg (Dehydroacetic Acid) to

each of 4 dogs-2 orally, or intravenously, in a further study phase single IV doses of 20 to 480 mg/kg

Dehydroacetic Acid (as Sodium Dehydroacetate) were given to 6 dogs. The collection and analysis of

blood samples revealed rapid absorption, with maximum plasma concentrations (approximately 22 to

26 mg/l00 ml) occurring 1.5 to 2 hours after administration and diminishing slowly thereafter; traces of

Dehydroacetic Acid remained after 3 to 4 days (doses of 80 mg/kg and above).

Reference 4

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

Circa 1950

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Objective of study:

absorption

toxicokinetics

Qualifier:

no guideline available

Principles of method if other than guideline:

Basic toxicokinetic study

GLP compliance:

no

Specific details on test material used for the study:

Dehydroacetic Acid (DHA-Na)

Radiolabelling:

no

Species:

rat

Strain:

not specified

Details on species / strain selection:

not specified

Sex:

not specified

Details on test animals or test system and environmental conditions:

not specified

Route of administration:

oral: feed

Vehicle:

not specified

Duration and frequency of treatment / exposure:

Daily in diet for minmum 12 days - data from a chronic 2-year rat study is also cited in the publication.

Dose / conc.:

200 ppm (nominal)

Remarks:

Dosages in diet: 0.02, 0.05. 0.1 or 0.2% by weight (equivalent to 200, 500, 1000 or 2000 ppm or 20, 50, 100 or 200 mg/kg bw/day DHA equivalent)

Dose / conc.:

500 ppm (nominal)

Dose / conc.:

1 000 ppm (nominal)

Dose / conc.:

2 000 ppm (nominal)

No. of animals per sex per dose / concentration:

12

Control animals:

not specified

Positive control reference chemical:

not specified

Details on study design:

See below

Details on dosing and sampling:

Rats in four groups of 12 each were fed diets containing 0.02, 0.05, 0.1, and 0.2 percent Dehydroacetic Acid (as Sodium Dehydroacetate). Two rats from each group were killed every 2 days for 12 days, and total Dehydroacetic Acid intake
and blood plasma concentrations were determined.

Statistics:

not specified

Type:

absorption

Results:

See below

Details on absorption:

Plasma concentrations increased correspondingly with increased dose. Maximum plasma concentrations of Dehydroacetic Acid from low dose to high were approximately 6, 8, 11, and 18 mg/l00 ml, respectively. Mean Dehydroacetic Acid plasma concentrations in rats on a 2-year chronic oral toxicity study were directly related to the doses of 0.02, 0.05, and 0.1 percent Dehydroacetic Acid. Mean plasma concentrations (determined after 730 days) for the males from low to high dose were
0.4, 1.6, and 5.8 mg/l00 ml, respectively; means for the females were 0.8, 3.2, and 10 mg/l00 ml, respectively.

Details on distribution in tissues:

Not specified.

Details on excretion:

Not specified.

Metabolites identified:

not specified

Bioaccessibility (or Bioavailability) testing results:

Not specified.

Conclusions:

For DHA-Na fed in the diet to rats at 0.02, 0.05. 0.1 or 0.2% by weight (equivalent to 200, 500, 1000 or 2000 ppm or 20, 50, 100 or 200 mg/kg bw/day) plasma concentrations of DHA increased correspondingly with increased dose.
Maximum plasma concentrations of Dehydroacetic Acid from low dose to high were approximately 6, 8, 11, and 18 mg/l00 ml, respectively.
In a 2-year rat study measured DHA plasma concentrations were directly related to the doses of 0.02, 0.05, and 0.1 percent Dehydroacetic Acid.

Executive summary:

 

In basic TK studies conducted in the rat, via the feed, DHA-Na at 0.02, 0.05. 0.1 or 0.2% by weight (equivalent to 200, 500, 1000 or 2000 ppm or 20, 50, 100 or 200 mg/kg bw/day) led to increased plasma concentrations of DHA corresponding with increased dose. Maximum plasma concentrations of Dehydroacetic Acid from low dose to high were approximately 6, 8, 11, and 18 mg/l00 ml, respectively. In a further study, a 2-year rat study, measured DHA plasma concentrations were directly related to the doses of 0.02, 0.05, and 0.1% Dehydroacetic Acid.

Reference 5

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

Circa 1950

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Objective of study:

absorption

toxicokinetics

Qualifier:

no guideline available

Principles of method if other than guideline:

Basic toxicokinetic study

GLP compliance:

no

Specific details on test material used for the study:

Dehydroacetic acid and sodiun dehydroacetate used.

Radiolabelling:

no

Species:

rat

Strain:

not specified

Sex:

not specified

Details on test animals or test system and environmental conditions:

Not specified.

Route of administration:

dermal

Vehicle:

other: Greaseless ointment base or water. No detail on ointment base - trade name at the time was Neobase.

Details on exposure:

On skin for 24 hours.

Duration and frequency of treatment / exposure:

Once for 24 hours.

Dose / conc.:

1 other: g/kg

Remarks:

50% suspension DHA

Dose / conc.:

3 other: g/kg

Remarks:

50% suspension DHA

Dose / conc.:

5 other: g/kg

Remarks:

50% suspension DHA or sodium dehydroacetate in water.

No. of animals per sex per dose / concentration:

2

Control animals:

yes

Positive control reference chemical:

not specified

Details on study design:

A skin absorption study in rabbits was conducted by the Draize sleeve technique, with the exception that the animals were not restrained in their cages and the sleeves were wrapped in heavy cloth bandages. After a 24-hour exposure period, the sleeves were removed, and the skin was cleansed with soap and water. All rabbits were observed for 2 weeks afterwards. Dehydroacetic Acid was applied as a 50% suspension in a greaseless ointment base at doses of 1 .0, 3.0, and 5.0 g/kg.
Dehydroacetic Acid was applied as a 50 percent suspension in a greaseless ointment base at doses
of 1 .0, 3.0, and 5.0 g/kg. Sodium Dehydroacetate was also applied to 5 animals at a dose of 5.0 g/kg
in a water slurry.
All rabbits were observed for 2 weeks afterwards.

Details on dosing and sampling:

Draize sleeve technique, with the exception that the animals were not restrained in their cages and the sleeves were wrapped in heavy cloth bandages. No specific detail was included on blood sampling.

Statistics:

not specified

Type:

absorption

Details on absorption:

Equimolar concentrations of both compounds were absorbed to the same degree from a washable base. Absorption of Dehydroacetic Acid did not differ greatly between washable base or white petrolatum vehicles; approximately 50 percent more Sodium Dehydroacetate was absorbed from the washable base than from the aqueous solution. Doses ranged from 0.01 to 2.0 g/kg, and concentrations of Dehydroacetic Acid applied were 0.1, 1 .0, and 10.0 percent. The plasma Dehydroacetic
Acid concentrations increased correspondingly with increasing dose and concentration.

Details on distribution in tissues:

not specified

Details on excretion:

not specified

Metabolites identified:

not specified

Bioaccessibility (or Bioavailability) testing results:

not specified

Animals of the 1 .0 and 3.0 g/kg groups had only slight and transitory weight loss. One of the two rabbits exposed to the 5.0 g/kg dose died.

Conclusions:

Equimolar concentrations of both compounds were absorbed to the same degree.
Absorption of Dehydroacetic Acid did not differ greatly between washable base or white petrolatum vehicles; approximately 50 percent more Sodium Dehydroacetate was absorbed from the washable base than from the aqueous solution.
The plasma Dehydroacetic Acid concentrations increased correspondingly with increasing dose and concentration.

Executive summary:

Evidence from dermal application (occluded) of either DHA or DHA-Na to rabbits demonstrated absorption through skin. Equimolar concentrations of both compounds were absorbed to

about the same degree from a washable base or white petrolatum vehicles. Approximately 50 percent more Sodium Dehydroacetate was absorbed from the washable base than from the aqueous solution.

The plasma Dehydroacetic Acid concentrations increased correspondingly with increasing dose and concentration.

Reference 6

Endpoint:

basic toxicokinetics, other

Remarks:

Plasma protein binding

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

Circa 1950

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Objective of study:

absorption

toxicokinetics

Qualifier:

no guideline followed

Principles of method if other than guideline:

Asessment of basic toxicokinetics and plasma protein binding

GLP compliance:

no

Specific details on test material used for the study:

Dehydroacetic Acid and Sodium Dehydroacetate

Radiolabelling:

other: a radioactive label is mentioned for one experiment but little detial given

Species:

other: rat, human, dog

Strain:

not specified

Details on species / strain selection:

not specified

Sex:

not specified

Details on test animals or test system and environmental conditions:

not specified

Route of administration:

other: oral ingestion and intravenous

Vehicle:

not specified

Duration and frequency of treatment / exposure:

not specified

Dose / conc.:

80 other: mg/kg

Remarks:

These dosages are the only ones specified.

Dose / conc.:

240 other: mg/kg

Dose / conc.:

750 other: mg/kg

Remarks:

Human oral ingestion.

No. of animals per sex per dose / concentration:

not specified

Control animals:

not specified

Type:

distribution

Results:

Plasma protein binding.

Metabolites identified:

not specified

Conclusions:

The data suggests that dehydroacetic acid, in rats, human and dogs, is bound to plasma proteins (not ably serum albmin and globulins and that the percentage of binding varied inversely with total plasma DHA concentration.
Some data, in the dog, also suggested placental transfer of DHA and possible lactational transfer, however, this was in single animals only.

Executive summary:

DHA was dosed to either rats, dogs or humans, via the oral or intravenous routes at a range of

concentrations. The aim of the studies was to examine plasma protein binding of DHA.

The data from the varied studies suggests that dehydroacetic acid, in rats, human and dogs, is bound to

plasma proteins (notably serum albmin and globulins) and that the percentage of binding varied inversly

with total plasma DHA concentration. Some data, in the dog, also suggested placental transfer of DHA

and possible lactational transfer. However, this was in single animals only.

Reference 7

Endpoint:

basic toxicokinetics in vivo

Type of information:

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

Adequacy of study:

weight of evidence

Justification for type of information:

refer to analogue justification provided in IUCLID section 13

Reason / purpose for cross-reference:

read-across source

Type:

distribution

Results:

Plasma protein binding.

Reference 8

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

Circa 1966

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Objective of study:

metabolism

Qualifier:

no guideline followed

Principles of method if other than guideline:

Basic assessment of metabolism

GLP compliance:

no

Radiolabelling:

no

Species:

rat

Strain:

not specified

Sex:

female

Details on test animals or test system and environmental conditions:

not specified

Route of administration:

subcutaneous

Vehicle:

not specified

Duration and frequency of treatment / exposure:

Daily 7-10 days.

Dose / conc.:

200 mg/kg bw/day (nominal)

Control animals:

yes

Positive control reference chemical:

not specified

Details on study design:

DHA administered alone or following an intraperitoneal injection of 100 mg/kg hexobarbital - to examine the effects on liver metabolism.

Statistics:

not specified

Type:

metabolism

Details on absorption:

Not specified.

Details on distribution in tissues:

Effects demonstrated in the liver.

Details on excretion:

Not specified.

Metabolites identified:

not specified

Details on metabolites:

Not specified.

Bioaccessibility (or Bioavailability) testing results:

Not specified.

Dehydroacetic Acid produced a stimulating effect on drug-metabolizing enzymic activity.

The administration of Dehydroacetic Acid shortened the duration of the hypnotic state caused by 100 mg/kg hexobarbital injected intraperitoneally. The Dehydroacetic Acid-treated rats had higher activity of N-demethylation of aminopyrine, hydroxylation of hexobarbital or cyclobarbital, aromatic hydroxylation of aniline, and hydrolysis of parathion by the liver than had controls. Dehydroacetic Acid increased the glycogen content but had no effect on the fat content of the liver.

Conclusions:

Subcutaneous administration of 200 mg/kg DHA had a stimulating effect on drug-metabolizing enzymic activity, reduced the effects induced by hexobarbital injection and induced higher activity of N-demethylation of aminopyrine, hydroxylation of hexobarbital or cyclobarbital, aromatic hydroxylation of aniline, and hydrolysis of parathion by the liver than had controls.

Executive summary:

In female rats, subcutaneous administration of 200 mg/kg DHA had a stimulating effect on drugmetabolizing enzymic activity, reduced the effects induced by hexobarbital injection and induced higher

activity of N-demethylation of aminopyrine, hydroxylation of hexobarbital or cyclobarbital, aromatic hydroxylation of aniline, and hydrolysis of parathion by the liver than had controls. Furthermore, DHA

treatment increased the glycogen content but had no effect on the fat content of the liver.

Reference 9

Endpoint:

basic toxicokinetics in vivo

Type of information:

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

Justification for type of information:

refer to analogue justification provided in IUCLID section 13

Reason / purpose for cross-reference:

read-across source

Type:

metabolism

Results:

Dehydroacetic Acid produced a stimulating effect on drug-metabolizing enzymic activity. The administration of Dehydroacetic Acid shortened the duration of the hypnotic state caused by 100 mg/kg hexobarbital injected intraperitoneally.

Reference 10

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

Circa 1950

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Objective of study:

excretion

Qualifier:

no guideline followed

Principles of method if other than guideline:

Basic assessment of excretion

GLP compliance:

no

Specific details on test material used for the study:

Dehydroacetic acid and Sodium dehydroacetate.

Radiolabelling:

no

Species:

other: publication included, dogs, monkeys and humans.

Strain:

not specified

Sex:

not specified

Details on test animals or test system and environmental conditions:

not specified

Route of administration:

other: Intravenous bolus and infusion, oral gavage, ingestion.

Vehicle:

not specified

Duration and frequency of treatment / exposure:

Details given in results.

Dose / conc.:

160 mg/kg bw/day (nominal)

Remarks:

Dog, oral and intravenous

Dose / conc.:

80 mg/kg bw/day (nominal)

Remarks:

Dog, intravenous

Dose / conc.:

50 mg/kg bw/day (nominal)

Remarks:

Monkey, oral

Dose / conc.:

100 mg/kg bw/day (nominal)

Remarks:

Monkey, oral

Dose / conc.:

200 mg/kg bw/day (nominal)

Remarks:

Monkey, oral

Dose / conc.:

6.1 mg/kg bw/day (nominal)

Remarks:

Human, oral, low dose range

Dose / conc.:

12.5 mg/kg bw/day (nominal)

Remarks:

Human, oral, high dose range

No. of animals per sex per dose / concentration:

not specified

Control animals:

not specified

Positive control reference chemical:

not specified

Details on study design:

see results

Details on dosing and sampling:

seee results

Statistics:

not specified

Type:

excretion

Results:

See results section below.

Details on excretion:

Total urinary excretion was only 15 to 20 percent of single oral and intravenous doses of 160 mg/kg Dehydroacetic Acid (as Sodium Dehydroacetate) to the dog, approximately half of which was excreted in the first 24 hours. After daily oral and intravenous doses of 80 mg/kg Dehydroacetic Acid (as Sodium Dehydroacetate) to 4 dogs, excretion was no greater than 20 percent of the daily dose. Monkeys receiving 50, 100, and 200 mg/kg Dehydroacetic Acid or Sodium Dehydroacetate (doses represent weight of Dehydroacetic Acid) by stomach tube 5 days per week had the same renal elimination of Dehydroacetic Acid as the dog. Samples of urine were collected from 3 men ingesting Dehydroacetic Acid at doses ranging from 6.1 to 12.5 mg/kg per day. The percentage of daily dose recovered in the urine varied between 12.4 and 29.2 (mean of 22.2). Comparatively, this was greater than that in monkeys and dogs. Furthermore, the percentage of dose of Dehydroacetic Acid or Sodium Dehydroacetate eliminated in a 24-hour period was dependent on the plasma concentration and, therefore, on daily intake. During continuous intravenous infusion in the dog of 0.5 mg/kg per minute of Dehydroacetic Acid, maximum clearance was 1 ml per minute at plasma concentrations of 5 to 15 mg/l00 ml. An experiment on a single dog with calculations based on concentrations of “free” plasma Dehydroacetic Acid demonstrated that 98 to 99 percent of the dose was reabsorbed by the renal tubules. The clearance rates in 2 men ingesting Dehydroacetic Acid daily (1 receiving 200 to 400 mg Dehydroacetic Acid four times per day for 17 days) varied from 0.43 to 2.86 ml per minute (means of
1.49 and 1.14 ml per minute).

Metabolites identified:

not specified

Bioaccessibility (or Bioavailability) testing results:

not specified

Conclusions:

Total urinary excretion was only 15 to 20 percent of single oral and intravenous doses of 160 mg/kgDehydroacetic Acid to the dog, approximately half of which was excreted in the first 24 hours. After oral and intravenous doses of 80 mg/kg Dehydroacetic Acid to dogs, excretion was no greater than 20% of the daily dose. Monkeys receiving oral doses of 50, 100, and 200 mg/kg Dehydroacetic Acid or Sodium Dehydroacetate 5 days per week had the same renal elimination of Dehydroacetic Acid as the dog. The percentage of dose of Dehydroacetic Acid or Sodium Dehydroacetate eliminated in a 24-hour period was dependent on the plasma concentration and, therefore, on daily intake. In the dog, with calculations based on concentrations of “free” plasma Dehydroacetic Acid, it was shown that 98 to 99% of the dose was reabsorbed by the renal tubules.

Executive summary:

The elimination and excretion of DHA or DHA-Na was studied after administration (oral or intravenous) in man, dogs or monkeys.

Total urinary excretion was only 15 to 20 percent of single oral and intravenous doses of 160 mg/kgDehydroacetic Acid to the dog, approximately half of which was excreted in the first 24 hours. After oral and intravenous doses of 80 mg/kg Dehydroacetic Acid to dogs, excretion was no greater than 20% of the daily dose. Monkeys receiving oral doses of 50, 100, and 200 mg/kg Dehydroacetic Acid or Sodium Dehydroacetate 5 days per week had the same renal elimination of Dehydroacetic Acid as the dog. The percentage of dose of Dehydroacetic Acid or Sodium Dehydroacetate eliminated in a 24-hour period was dependent on the plasma concentration and, therefore, on daily intake. In the dog, with calculations based on concentrations of “free” plasma Dehydroacetic Acid, it was shown that 98 to 99% of the dose was reabsorbed by the renal tubules.

Reference 11

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

Circa 1963

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Objective of study:

excretion

metabolism

Qualifier:

no guideline followed

Principles of method if other than guideline:

Basic assessment of metabolism and excretion

GLP compliance:

no

Specific details on test material used for the study:

14C-DHA.

Radiolabelling:

yes

Species:

other: rats and rabbits

Strain:

not specified

Details on species / strain selection:

not specified

Sex:

not specified

Details on test animals or test system and environmental conditions:

not specified

Route of administration:

other: Oral and subcutaneous and intraperitoneal

Vehicle:

not specified

Duration and frequency of treatment / exposure:

Assumed single dose.

Dose / conc.:

20 mg/kg bw/day (nominal)

Remarks:

Low dose range, oral dose

Dose / conc.:

70 mg/kg bw/day (nominal)

Remarks:

High dose range, oral dose

Dose / conc.:

6.6 mg/kg bw/day (nominal)

Remarks:

Intraperitoneal

No. of animals per sex per dose / concentration:

not specified

Control animals:

not specified

Positive control reference chemical:

not specified

Statistics:

not specified

Type:

excretion

Results:

See other information on results section.

Type:

metabolism

Results:

See other information on results section.

Details on excretion:

See other information on results section.

Metabolites identified:

yes

Details on metabolites:

See other information on results section.

Dehydroacetic Acid labelled with14C (in four positions) was tested in both rats and rabbits. Oral doses of 20 to 70 mg/kg 14CDehydroacetic Acid were not rapidly excreted. Rabbits excreted 70 to 80% of the 14C label in the urine, 7 to 10% respiratory C02, and 2 to 3 percent in the feces after 3 to 7 days, leaving 8 to 11% in the tissues. Rats excreted 20 to 40% in the urine, 10 to 25% in respiratory C02, and 10 to 20% in the feces after 4 to 5 days, leaving 5 to 26% in the tissues. Three metabolites were identified from rabbit urine: triacetic acid lactone (TAL), a hydroxy-Dehydroacetic Acid, and a compound (designated metabolite X) believed to be the salt of TAL 3-carboxylic acid. Another metabolite (designated Y) was detected, determined not to be a pyrone, but not further identified. Dehydroacetic Acid and hydroxy-Dehydroacetic Acid occurred in the urine both as the free compounds and as the 1’-imino derivatives. Urine from rabbits contained an average of 5% Dehydroacetic Acid of the administered dose, 20 percent hydroxy-Dehydroacetic Acid, 10% TAL, 0.3% urea, and 20 and 15% of metabolites X and Y, respectively. Urine from rats contained 5% Dehydroacetic Acid, 8% hydroxy-Dehydroacetic Acid, 1% TAL, and 0.3% urea. The percentages of dose excreted as Dehydroacetic Acid and hydroxy-Dehydroacetic Acid

markedly increased with increasing doses, while that of X and Y decreased correspondingly. Subcutaneous injection of Dehydroacetic Acid resulted in a pattern of metabolite excretion similar to

that following oral administration. Dehydroacetic Acid and hydroxy-Dehydroacetic Acid were excreted in the bile because these two compounds, but not TAL, were isolated from the feces and gut contents of rats after subcutaneous injection. In additional experiments using rats, the bile contained an average of 8% of a 6.7 mg/kg intraperitoneally administered dose of 14C-Dehydroacetic Acid.

Conclusions:

14C-Dehydroacetic Acid was not rapidly excreted. Rabbits excreted 70 to 80% in the urine, 7 to 10% respiratory C02, and 2 to 3% percent in the feces,
with 8 to 11% in the tissues. Rats excreted 20 to 40% in the urine, 10 to 25% in respiratory C02, and 10 to 20% in the feces with 5 to 26% in the tissues.
Four metabolites were identified from rabbit urine: triacetic acid lactone (TAL), a hydroxy-Dehydroacetic Acid, and a compound (designated metabolite X) believed to be the salt of TAL 3-carboxylic acid plus a metabolite designated Y. Urine from rabbits contained an average of 5% Dehydroacetic Acid of the administered dose, 20% hydroxy-Dehydroacetic Acid, 10% TAL, 0.3% urea, and 20 and 15% of metabolites X and Y, respectively. Urine from rats contained 5% Dehydroacetic Acid, 8% hydroxy-Dehydroacetic Acid, 1% TAL, and 0.3% urea. The percentages of dose excreted as Dehydroacetic Acid and hydroxy-Dehydroacetic
Acid markedly increased with increasing doses, while that of X and Y decreased correspondingly.

Executive summary:

Dehydroacetic Acid (14C labelled) was administered to rats or rabbits either orally, or by injection (sc or ip). Oral doses were 20 to 70 mg/kg whilst ip injection was 6.7 mg/kg (the sc dose was not given).

14C-Dehydroacetic Acid was not rapidly excreted. Rabbits excreted 70 to 80% in the urine, 7 to 10% respiratory C02, and 2 to 3% percent in the feces after 3 to 7 days, leaving 8 to 11% in the tissues. Rats excreted 20 to 40% in the urine, 10 to 25% in respiratory C02, and 10 to 20% in the feces after 4 to 5 days, leaving 5 to 26% in the tissues. Three metabolites were identified from rabbit urine: triacetic acid lactone (TAL), a hydroxy-Dehydroacetic Acid, and a compound (designated metabolite X) believed to be the salt of TAL 3 -carboxylic acid. Another metabolite (designated Y) was detected, determined not to be a pyrone, but not further identified. Dehydroacetic Acid and hydroxy-Dehydroacetic Acid occurred in the urine both as the free compounds and as the 1’-imino derivatives. Urine from rabbits contained an average of 5% Dehydroacetic Acid of the administered dose, 20% hydroxy-Dehydroacetic Acid, 10% TAL, 0.3% urea, and 20 and 15% of metabolites X and Y, respectively. Urine from rats contained 5% Dehydroacetic Acid, 8% hydroxy-Dehydroacetic Acid, 1% TAL, and 0.3% urea. The percentages of dose excreted as Dehydroacetic Acid and hydroxy-Dehydroacetic Acid markedly increased with increasing doses, while that of X and Y decreased correspondingly.

Reference 12

Endpoint:

basic toxicokinetics in vivo

Type of information:

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

Adequacy of study:

weight of evidence

Justification for type of information:

refer to analogue justification provided in IUCLID section 13

Reason / purpose for cross-reference:

read-across source

Type:

excretion

Results:

See other information on results section for source substance.

Type:

metabolism

Results:

See other information on results section for source substance.

Description of key information

Study 001: oral gavage study in the monkey; doses 50, 100 or 200 mg/kg bw/day, absorption evident with peak concentrations occurred at 4.5 and 7 days after dosing. Plasma levels were 15, 26 to 33, and 45 to 51 mg/100 ml from lowest to highest dosage and diminished rapidly.

Study 002: oral and intravenous study in the dog, Sodium Dehydroacetate, doses 20, 80, 160 or 480 mg/kg bw/day, analysis of blood samples revealed rapid absorption, with maximum plasma concentrations (approximately 22 to 26 mg/l00 ml) occurring 1.5 to 2 hours after administration and diminishing slowly thereafter; traces of Dehydroacetic Acid remained after 3 to 4 days (doses of 80 mg/kg and above).

Study 003: dietary study in the rat, Sodium Dehydroacetate, doses 0.02, 0.05. 0.1 or 0.2% by weight (equivalent to 200, 500, 1000 or 2000 ppm), plasma concentrations increased with increased dose.

Maximum plasma concentrations of DHA from low dose to high were approximately 6, 8, 11, and 18 mg/l00 ml, respectively. In a 2-year rat study measured DHA plasma concentrations were directly related to the doses of 0.02, 0.05, and 0.1 percent Dehydroacetic Acid.

Study 004: dermal study in the rabbit, 50% suspension DHA or DHA-Na in water doses 1, 3 or 5 g/kg. Both compounds were absorbed to the same degree. Absorption of Dehydroacetic Acid did not

differ greatly between washable base or white petrolatum vehicles used; approximately 50 percent more Sodium Dehydroacetate was absorbed from the washable base than from the aqueous solution. The plasma Dehydroacetic Acid concentrations increased correspondingly with increasing dose and concentration.

Study 005: studies in the rat, human and dog. The data from the varied studies suggests that dehydroacetic acid, in rats, human and dogs, is bound to plasma proteins (notably serum albmin and globulins) and that the percentage of binding varied inversly with total plasma DHA concentration. Some data, in the dog, also suggested placental transfer of DHA and possible lactational transfer. However, this was in single animals only.

Study 006: study in the rat; DHA administered alone (200 mg/kg bw/day) or following an intraperitoneal injection of 100 mg/kg hexobarbital - to examine effects on liver metabolism. DHA had a stimulating

effect on drug metabolizing enzymic activity, reduced the effects induced by hexobarbital injection and induced higher activity of N-demethylation of aminopyrine, hydroxylation of hexobarbital or cyclobarbital, aromatic hydroxylation of aniline, and hydrolysis of parathion by the liver than had controls. DHA also increased the glycogen content but had no effect on the fat content of the liver.

Study 007: key data from the study included dogs and monkeys, treatments were by intravenous bolus injection or infusion or oral gavage. Excretion via the urine was examined. Data from dogs and monkeys were similar with about 15 to 20% excretion via the urine. The percentage of dose of Dehydroacetic Acid or Sodium Dehydroacetate eliminated in a 24-hour period was dependent on the plasma concentration and, therefore, on daily intake.

Study 008: study in the rat and rabbit, via oral, subcutaneous or intraperitoneal routes, radiolabelled test material used. 14C-Dehydroacetic Acid was not rapidly excreted. Rabbits excreted 70 to 80% in the

urine, 7 to 10% respiratory C02, and 2 to 3% percent in the feces, with 8 to 11% in the tissues. Rats excreted 20 to 40% in the urine, 10 to 25% in respiratory C02, and 10 to 20% in the feces with 5 to 26%

in the tissues. Four metabolites were identified from rabbit urine.

Key value for chemical safety assessment

Bioaccumulation potential:

low bioaccumulation potential

Absorption rate - oral (%):

100

Absorption rate - dermal (%):

50

Absorption rate - inhalation (%):

100

Additional information

The weight of evidence suggests that dehydroacetic acid (DHA) or sodium dehydroacetate are rapidly and well absorbed after oral exposure and may be bound to plasma proteins (albumin and globulins). Data from the rabbit and rat, using 14C labelled test material, suggested that in the rabbit the oral absorption was 87 to 104% and for the rat was 45 to 111%. The weight of evidence from this package of studies suggests that an oral absorption of 90% is a reasonable conservative conclusion to arrive at.

The liver appears to be a target tissue and, in the rat, DHA was demonstrated to have enhanced some elements of liver metabolism. A small number of metabolites were isolated, in one study, but were not

completely characterised. There was no conclusive evidence of significant bioaccumulation in specific target organs or tissues and excretion was demonstrated to be mostly via the urine and feces with a

significant amount (i.e. as 14C) via respiratory CO2.

A study in the rabbit suggested that dermal absorption of the test material was evident but there was no definitive estimation as to the extent of absorption. However, comparison of the acute oral and dermal toxicity data would suggest that dermal absorption may be significantly less than oral absorption, i.e. the systemic dose of DHA would be markedly different in comparison to a similar dose via the oral route. Taking this into consideration and with reference to both the EFSA 2017 Guidance on dermal absorption (EFSA Journal 2017;15(6):4873)) and the ECHA 2017 Guidance on Information Requirements and Chemical Safety Assessment (Chapter R.7c: Endpoint specific guidance Version 3), a reasonably conservative estimate of dermal absorption can be concluded as 50%.