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Assessment of the toxicokinetic behaviour of 2-(2-hexyl-decyloxy)-benzamide (CAS-No. 202483-62-3)

 

There were no studies available in which the toxicokinetic properties of 2-(2-hexyl-decyloxy)-benzamide SP-334/TS-2863) were investigated. Therefore, the toxicokinetic behavior of the substance has been assessed taking into account the available information on physicochemical and toxicological characteristics, according to ‘Guidance on information requirements and chemical safety assessment Chapter R.7c: Endpoint specific guidance’ (ECHA, 2008).

2-(2-hexyl-decyloxy)-benzamide (molecular weight of 361.56 g/mol) is a white powder, which is insoluble in water (< 0.006 mg/L). The log Pow is 7.38, indicating that a general bioaccumulation of 2-(2-hexyl-decyloxy)-benzamide is likely to occur. The dissociation constant pKa1: 0.85 at 20 °C, as calculated with SPARC (Karickhoff, 2009), leads to the conclusion that the substance will be uncharged at intestinal pH values.

 

Absorption

In an acute oral toxicity study (limit test performed according to OECD 423), rats were administered 2-(2-hexyl-decyloxy)-benzamide by gavage. The LD50 was determined to be 5000 mg/kg bw, based on the LD50 cut-off value set according to OECD 423 (Pels Rijken, 1998). No mortality occurred and no gross pathological abnormalities were recorded. Lethargy, uncoordinated movements and hunched posture were observed in all animals until 4 hours after dosing. Also, no mortality or clinical signs of toxicity were observed during a 28-day repeated dose toxicity study in male and female rats administered up to 1000 mg/kg bw/d by gavage. Similarly, no treatment-related effects were observed in a screening reproduction toxicity study during which males were exposed for 28 days and females up to 56 days to a max dose of 1000 mg/kg bw/d by gavage (1998e). As a consequence of the low water solubility and the absence of signs of systemic toxicity, the bioavailability of 2-(2-hexyl-decyloxy)-benzamide in the gastrointestinal tract after single and repeated oral administration is expected to be very low; which is in line with the assumption of a low absorption percentage due to the relatively high log Pow.

In an acute dermal toxicity study (OECD 403, limit test) 2000 mg/kg bw 2-(2-hexyl-decloxy)-benzamide was administered to rabbits (Pels Rijken, 1998). No mortality or signs of systemic toxicity were observed, even at this high dose, indicating a very low dermal toxicity. The QSAR tool DERMWIN v4.1, considering molecular weight, log Po/w and water solubility, calculated a very low dermal absorption rate of 3.06 x 10-5 µg/cm2/h (EPA, 2011). Taking the experimental very low acute dermal toxicity and the calculated very low dermal absorption rate into account, the dermal absorption is considered to be negligible.

An accurate vapour pressure could not be determined due to the low water solubility and was also difficult to calculate, but was estimated to be < 0.0001 hPa at 20 ºC (Krips, 1998), indicating that exposure due to evaporation is not likely. As the substance is a powder with an inhalable fraction (91% < 100 µm), exposure via the inhalative route is possible. However, as less than 0.7% of the particles are smaller than 4 µm, very few of the particles are expected to reach the lungs (bronchioles). Most of the particles will be trapped on the mucous membrane in the trachea and bronchi, from where they will be transported by ciliary movement upwards to the throat and be swallowed or coughed out. Based on these data, the absorption of the substance via the inhalative route is considered to be negligible.

 

Metabolism

The potential metabolites following enzymatic metabolism of 2-(2-hexyl-decyloxy)-benzamide were calculated using the QSAR OECD toolbox (OECD, 2011). This QSAR tool predicts which metabolites of the test substance may be created by enzymes in the liver and in the skin, and by intestinal bacteria in the gastrointestinal tract. No metabolites were predicted. Furthermore, it is likely that 2-(2-hexyl-decyloxy)-benzamide will not be absorbed from the gastrointestinal tract into the blood to any significant extent and will therefore be excreted unchanged via the faeces.

Studies on genotoxicity (Ames test, gene mutation in mammalian cells in vitro, chromosome aberration assay in mammalian cells in vitro) were negative, with and without metabolic activation (Verspeek-Rijp, 1998; Bednáriková, 2011; Bertens,1998). There is no indication that 2-(2-hexyl-decyloxy)-benzamide is activated to reactive intermediates under the relevant test conditions. The same conclusion can be drawn from the skin sensitisation study (Pels Rijcken, 1998).

 

Excretion

As the test substance is not bioavailable, it will most likely be excreted unchanged via the faeces.

 

Reference list

 

ECHA. Guidance on information requirements and chemical safety assessment. Chapter R.7c: Endpoint specific guidance. May 2008. Downloaded from:

http://guidance.echa.europa.eu/docs/guidance_document/information_requirements_en.htm?time=1284647204

EPA. DERMWIN 4.1, Epi Suite 4.10. Calculation performed July 2011. http://www.epa.gov/opptintr/exposure/pubs/episuite.htm

 

Karickhoff, S.W. (Ed.) SPARC Online calculator (v4.5.1522, 2009). University of Georgia, USA. Calculation performed 08 July 2011.

http://archemcalc.com/sparc/    

 

OECD. (Q)SAR Toolbox (v2.1, 2011). Developed by Laboratory of Mathematical Chemistry, Bulgaria for the Organisation for Economic Co-operation and Development (OECD). Calculation performed 12 July 2011.

http://toolbox.oasis-lmc.org/?section=overview