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Administrative data

Link to relevant study record(s)

Reference
Endpoint:
basic toxicokinetics
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reason / purpose:
read-across source
Type:
absorption
Results:
For risk assessment purposes: oral absorption 100%, inhalation absorption 100% and dermal absorption 10%
Conclusions:
The absorption factors for risk assessment purposes for Amphoacetates C8-C18 have been set by a certified toxicologist for risk assessment purposes: oral absorption 100%, inhalation absorption 100% and dermal absorption 10%. These values are read across to the registered substance.

Description of key information

A toxicokinetic assessment of a substance analogue (amphoacetates C8-C18) in accordance with the Guidance on information requirements and chemical safety assessment Chapter R.7c: Endpoint specific guidance was considered appropriate to assess the toxicokinetic properties of the substance. The absorption factors for risk assessment purposes: oral absorption 100%, inhalation absorption 100% and dermal absorption 10%.

Key value for chemical safety assessment

Absorption rate - oral (%):
100
Absorption rate - dermal (%):
10
Absorption rate - inhalation (%):
100

Additional information

Substance for which the toxicokinetic assessment is performed

Common name

Amphoacetates C12 -C14

EC number

Not yet assigned

(Alternate) CAS number(s)

66161 -62 -4; 68608 -66 -2

IUPAC name

Reaction products of 1H-Imidazole-1-ethanol, 4,5-dihydro-, 2-(C11-C13 odd-numbered alkyl) derivs. and sodium hydroxide and chloroacetic acid

Source chemical

Common name

Amphoacetates C8-18

Common name

Alkylamidoamine glycinate

EC number

931-291-0

CASnumber

Not available

IUPAC name

Reaction products of 1H-Imidazole-1-ethanol, 4,5-dihydro-, 2-(C7-C17 odd-numbered, C17-unsatd. alkyl) derivs. and sodium hydroxide and chloroacetic acid

 

Based on their structural similarity, physico-chemical and toxicological properties, these 2 substances are considered analogues. The toxicokinetic properties of Alkylamidoamine glycinate were determined based on the available physico-chemical properties and toxicological data.

 

Basic toxicokinetics

In general, a compound needs to be dissolved before it can be taken up from the gastro-intestinal tract after oral administration. The relatively small molecular weight (between 367 and 446 for the different forms) and the high water solubility (1 kg/L) are favourable for oral absorption. Because the substance has surface-active properties and a complex composition with multiple constituents, a log Kow could not be determined by the standard experimental methods. However estimates showed a higher solubility in water than in n-octanol. However, based on the moderate lipophilic character of the main surfactant compound expected from the presence of a hydrophobic alkyl chain structure Alkylamidoamine glycinate has the potential to be absorbed by passive diffusion. In contrast, ionization of Alkylamidoamine glycinate will impair the uptake since compounds need to pass the lipid membranes in the gastrointestinal wall (Reference:, Amidon GL. Mechanistic approach to understanding the factors affecting drug absorption: a review of fundamentals. J Clin Pharmacol 2002; 42: 620-43). Overall, it is likely that Alkylamidoamine glycinate is absorbed from the gastro-intestinal tract to a certain extent. Slight variations observed in the liver weights and clinical chemistry in the 28-day repeated dose toxicity study provided some evidence of a potential absorption by the oral route. For risk assessment purposes oral absorption of Alkylamidoamine glycinate is set at 100%. The results of the toxicity studies do not provide reasons to deviate from this proposed oral absorption factor.

 

Once absorbed, distribution of the substance throughout the body is expected based on its relatively low molecular weight. Based on its relatively hydrophilic character, extracellular concentration is expected to be higher than intracellular concentration. Absorbed Alkylamidoamine glycinate might undergo conjugation. The conjugates will either be excreted via the bile (high molecular weight compounds) or the urine (low molecular weight compounds; Reference: ECB EU Technical Guidance Document on Risk Assessment, 2003).

 

The boiling point could not be determined, but decomposition starts at 160°C. Due to the relatively low vapour pressure and since the substance is produced and used only as an aqueous solution, it is not likely that Alkylamidoamine glycinate will reach the nasopharyngeal region or subsequently the tracheobronchial or pulmonary region. If Alkylamidoamine glycinate reaches the tracheobronchial region, absorption through aqueous pores will be limited, taking the molecular weight of > 200 into account. However, the high water solubility of Alkylamidoamine glycinate (1 kg/L) is favourable for dissolution of the substance in the mucus lining of the respiratory tract. In addition, based on the structure of the main constituents and the presence of hydrophobic and hydrophilic parts Alkylamidoamine glycinate has the potential of crossing the alveolar and capillary membranes by passive diffusion. If Alkylamidoamine glycinate is inhaled, absorption of the substance is expected to be limited. For risk assessment purposes the inhalation absorption of Alkylamidoamine glycinate is set at 100%.

The substance has the potential to partition from the stratum corneum into the epidermis, enhanced by the high water solubility (1 kg/L). Due to the complexity of the UVCB substance and presence of inorganic salt a realistic logKow value could not be determined experimentally. However, the moderate lipophilic character of the surfactant constituents with various lengths of a lipohilic alkyl chain may indicate that the transfer between the stratum corneum and the epidermis could occur for some of the constituents. As a first approach, based on the molecular weight (between 367 and 446 for the different forms of the major constituents), the criteria for 10% dermal absorption as given in the TGD (Reference: ECB EU Technical Guidance Document on Risk Assessment, 2003; MW > 500 and log Pow< -1 or > 4) are not met. However, high water solubility and ionization state are expected to influence significantly the dermal absorption potential. The presence of charges has been shown to reduce dramatically the passage across the skin (Reference: H. Schaefer, T. E. Redelmeier (eds). In: Skin Barrier – Principles of percutaneous absorption.S. Krager AG (publ.), 1996). As produced or under the use conditions the surfactant part of the substance will be either as a sodium salt, or as an amphoteric form with positive and negative charges, therefore less likely to be absorbed. This is fully supported by experimental data on a structurally related amphoteric surfactant, dodecylamidopropylbetaine (CAS# 4292-10-8) showing a dermal absorption of less than 3.5% in Wistar rats (Reference: HERA (Human and Environmental Risk Assessment on ingredients of household cleaning products), 2005, http://www.heraproject.com/RiskAssessment.cfm). This result is considered relevant for the substance to propose a dermal absorption factor of 10% for risk assessment purposes.

The read-across from this analogue to the registered substance for the dermal, oral and inhalation absorption factors of the substance is considered scientifically justified based on the overall information available (see Section 13 for the read across rationale).