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Link to relevant study record(s)

Description of key information

According to MAK (2019):

After oral administration less than 1.5% was excreted with the faeces after 32 h, despite the detection of metabolites in the gastrointestinal tract. This suggests an enterohepatic cycle, and the oral absorption is practically complete (at least 98.5%). The half-life of the entire radioactivity in plasma was about 2 h. At 10 mg/kg bw, the bioavailability was 100%, at the higher dose it could not be calculated. In another oral study, the highest concentrations were measured in the intestine and kidneys after 4 and 8 h. MCA was bound to plasma albumin. In the first 24 h, 90% of the dose was excreted in the urine. After 48 h significant amounts of radioactivity were still found in the tissues.

With an epicutaneous, occlusive, maximum 4-h application of 125 mg radioactively-labeled MCA/kg bw in acetone in rats, a bioavailability of 90% was determined.

Based on an in vitro study the dermal uptake of MCA was estimated to be 3.7 mg in case of 2000 cm2 skin surface exposed to a 0.5% non-irritating solution of MCA for one h. For corrosive substances, according to the CLP regulation skin irritation is to be expected at 1% and higher. With linear extrapolation of the flux of 0.37 µg/cm2.h, for a non-irritating 0.5% solution, the uptake would be 3.7 mg in case of exposure of 2000 cm2 during one h.

In mice, MCA is metabolized into S-carboxymethylcysteine and thiodiacetic acid which are excreted in the urine. Other metabolites are glycolic acid, oxalic acid and CO2 (MAK justification 1998). In case of the biliary metabolites found in rats after intravenous administration of neutralized MCA, these are probably glutathione conjugates. About 60% of the administered dose was metabolized.  

Key value for chemical safety assessment

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

Additional information