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Reference
Endpoint:
basic toxicokinetics
Type of information:
experimental study
Adequacy of study:
key study
Study period:
January 2004
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
data from handbook or collection of data
Remarks:
The qualitative judgement is based on physico-chemical characteristics. Some of these are determined under conditions which are not biologically relevant (like the octanol/water partition coefficient at pH 11). Furthermore, the submission substance is a multi constituent substance while physico-chemical characteristics in general refer to pure substances. This limits the reliability of the assessment.
Objective of study:
toxicokinetics
Principles of method if other than guideline:
Qualitative judgement on the toxicokinetic behaviour based on physico-chemical characteristics.
GLP compliance:
no
Specific details on test material used for the study:
No further data
Radiolabelling:
no

The acute oral toxicity test with the test substance showed the LD50 being between 200 and 2000 mg/kg body weight. The subacute toxicity test for 28-days revealed a NOAEL of 50 mg/kg/day. Therefore, an extensive toxicokinetic assessment is considered of limited value. Below, a summary of the anticipated toxicokinetic behaviour of the test substance is given.

The water solubility of the test substance is high. Since in general a compound needs to be dissolved before it can be taken up from the gastro-intestinal tract, it is likely that the test substance will show a high systemic exposure after oral administration. It is to be expected that the oral bioavailability of the test substance will be relatively high. The highest absorption is expected to be from the duodenum.

In the gastro-intestinal tract, hardly any degradation of the substance is to be expected. In the case absorption of the test substance occurs, the aliphatic carbons as well as the primary nitrogens will undergo extensive hydroxylation, followed by rapid sulfation or glucuronidation. Direct conjugation at the nitrogens in the parent compound is expected. Also extensive cleavage of the ether bonds is anticipated. The resulting metabolites will be extensively excreted via bile and/or urine.
The submission substance will show a low volume of distribution, because of the relatively low lipophilicity of the compound.
The volume of distribution is expected to equal total body water (about 700 ml/kg). Accumulation in fatty tissues is therefore not anticipated. The plasma protein binding is expected to be low.

Uptake via inhalation may take place based on the vapour pressure.


Since it is generally accepted that substances with log Po/w ranging from 0.1 to 6 penetrate the skin easily, it is to be expected that the test substance may penetrate the skin rapidly. The fact that the test substance is corrosive to the skin may even increase the dermal absorption.

Based on the expected kinetic behaviour in the body, as described above, the test substance will show a relatively high absorption after oral administration, mainly because of its high water solubility. If absorption occurs, the test substance will be extensively metabolised in the liver and rapidly excreted via bile and/or urine. Therefore, accumulation in the body during prolonged exposure will be very low.

Conclusions:
Following a qualitative judgement based on physico-chemical characteristsc of the submission substance, the substance will show a relatively high absorption after oral administration, mainly because of its high water solubility. If absorption occurs, the test substance will be extensively metabolised in the liver and rapidly excreted via bile and/or urine. Therefore, accumulation in the body during prolonged exposure will be very low. Dermal absoprtion is also expected to be significant, following the logPow and skin corrosive properties of the submission substance.

Description of key information

Following a qualitative judgement based on physico-chemical characteristics of the submitted substance (Groen, 2004), the substance will show a relatively high absorption after oral administration, mainly because of its high water solubility. If absorption occurs, the test substance will be extensively metabolised in the liver and rapidly excreted via bile and/or urine. Therefore, accumulation in the body during prolonged exposure will be very low. Dermal absorption is expected to be significant, following the log Pow and skin corrosive properties of the submitted substance.

Key value for chemical safety assessment

Bioaccumulation potential:
low bioaccumulation potential
Absorption rate - oral (%):
100
Absorption rate - dermal (%):
100
Absorption rate - inhalation (%):
100

Additional information

Physico-chemical characteristics in general refer to a pure substance. As the submission substance is a multi-constituent substance the physico-chemical characteristics obtained may not be representative for all components in the submission substance. The qualitative assessment provided in this summary should thus be treated with care.

Some physico-chemical parameters are determined under conditions which are not biologically relevant (log octanol/water partition coefficient at pH 11; water solubility at pH 12.5), further limiting the reliability of the qualitative assessment.

XTJ 568 (CAS 897393-42-9; EC 447-920-2) is a colorless liquid with a moderate molecular weight of 220 g/mol, a high water solubility of 1000 g/L (at 20°C and pH 12.5). The partition coefficient was determined to be log Kow of 2 at pH 11 and the vapour pressure was assessed to be 3.4 Pa at 20°C.

The acute oral toxicity test with the test substance showed the LD50 being between 200 and 2000 mg/kg body weight. The subacute toxicity test for 28 days revealed a NOAEL of 150 mg/kg/day. The results of a primary skin irritation/ corrosion test on male rabbits indicate that the test substance is corrosive a classified as category 1B. Below a summary of the anticipated toxicokinetic behaviour of the test substance is given.

Oral absorption

XTJ 568 has a moderate partition coefficient of log Kow 2 (–1 < log Kow < 4) and a molecular weight < 500 g/mol, indicating that it is favourable for absorption. The water solubility of the test substance is high (>1000 mg/L) which would lead to dissolution of the substance into the gastrointestinal fluids and absorption through passive diffusion. It is, thus likely that the test substance will show a high systemic exposure after oral administration.

Treatment of Wistar rats with the substance for 28 consecutive days by oral gavage at dose levels of 50, 150 and 1000 mg/kg/day resulted in the premature sacrifice or death of all high dose animals (Van Otterdijk, 2003). Stomach effects (forestomach hyperplasia and ulceration) were considered to be contributory to death or the retarded health condition of these animals. In the 150 mg/kg/day dose group in this subacute study, piloerection, hunched posture, leanness and general swelling of the skin were observed but no stomach abnormalities were noted. There were no treatment related changes in performance of neurological functional.

Chase (2011) performed a subchronic 90-day oral toxicity study with the substance by daily gavage in the rat. The rats were administered for 90 consecutive days by oral gavage at dose levels of 0, 15, 50 and 150 mg/kg/day. This study also included enhanced sperm mobility and histopathology evaluations to clarify the results of the sperm evaluations from the two-generation reproductive toxicity study. There were no deaths to the study animals during the study. The appearance and behaviour of the animals were unaffected by treatment. Bodyweight gain, food consumption and organ weights were unaffected by treatment. There were no macroscopic or microscopic findings that were associated with treatment. Sensory reactivity, grip strength and motor activity were unaffected by treatment. There were no changes in the performance of neurological functional observations that were considered to be an effect of treatment. There were no effects of treatment on sperm number or morphology. The NOAEL was considered to be 150 mg/kg/day. This study supports the results of the 28 -day repeated dose test with a NOAEL of 150 mg/kg/day. The results of this study indicate that the substance is not a reproductive toxicant.

Based on the physicochemical properties and on the gastrointestinal effects reported in the 28 days study, the oral absorption factor is set to 100%.

 

Respiratory absorption

Given its low volatility (vapour pressure 3.4 Pa < 0.5 kPa), the availability of XTJ 568 for inhalation as a vapour is limited. Since XTJ 568 has a moderate partition coefficient of log Kow = 2 (-1 < log Kow < 4), it is favorable for absorption directly across the respiratory tract epithelium by passive diffusion and its very high water solubility will favour the rate at which the particles dissolve into the mucus determining the amount that could be absorbed directly when reaching the respiratory system.

Based on the physicochemical properties, the respiratory absorption factor is set to 100%.

 

Dermal absorption

Liquids are more readily taken up than solid. Because of its high solubility, XTJ 568 will dissolve easily into the surface moisture of the skin before uptake can take place.

It is expected that the penetration of XTJ 568 into the lipid rich environment of the stratum corneum will be favoured to a minor extent due to the limited lipophilic character (log Kow = 2) of the substance leading to a moderate dermal absorption. However, based on its high water solubility (>1000 mg/L), dermal uptake is expected to be moderate to high since the substance is soluble in water and will easily partition from the stratum corneum into the epidermis. Since this substance was also found to be corrosive to skin, the dermal absorption factor is set to 100%.

 

 Distribution

The high water solubility will favour the distribution of XTJ 568 through the body through aqueous channels and pores. The volume of distribution is expected to be equal to the total body water (about 700 ml/kg). Since the substance is not expected to be lipophilic (log Kow = 2), the substance will distribute into the cells to a limited extent. If absorption occurs, the target organs may be the liver before it would be rapidly excreted via bile and/or urine. The moderate log Kow and high water solubility would not favor accumulation in the body fatty tissues.

 

Metabolism

In the gastro-intestinal tract, hardly any degradation of the substance is to be expected. In the case of absorption of the test substance occurs, the aliphatic carbons as well as the primary nitrogens will undergo extensive hydroxylation, followed by rapid sulfation or glucuronidation. Direct conjugation at the nitrogens in the parent compound is expected. Also, extensive cleavage of the ether bonds is anticipated. The resulting metabolites will be extensively excreted via the bile and /or urine. The submission substance will show a low lipophilicity of the compound.