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Description of key information

Two oral administration studies on the absorption and excretion were performed in rats. One was done using the racemate and the other used both L- and D- form of the test substance.
For the racemate:
After single and repeated oral administration, the test substance (racemate) was rapidly absorbed from the gastrointestinal tract. Absorption, however, was incomplete amounting to about 17-33 % of the dose applied. The excretion of the test substance was rapid with a urinary excretion half-life of about 3-6 hours.
For L- and D- form:
After single oral administration of L-test substance or D-test substance both test animal groups showed a comparable level of rapid absorption and rapid renal excretion of the test substances. Based on the test results it can be concluded that L-test substance and D-test substance both have no bioaccumulation potential.

Key value for chemical safety assessment

Bioaccumulation potential:
no bioaccumulation potential

Additional information

The test substance is a racemate. Besides the racemate both L- and D- forms of the substance are available. Therefore two studies for oral administration were performed to evaluate the absorption and excretion. One study investigated the absorption and excretion of the racemate while the other investigated both L- and D- form of the test substance.

Both studies used male Wistar rats and evaluated the absorption and excretion of the substances by measuring the amount of substance in the urine.

After single and repeated oral administration of the racemate, a rapid absorbtion in the gastrointestinal tract could be detected. Absorption, however, was incomplete amounting to about 17-33 % of the dose applied. The excretion of the test substance was rapid with a urinary excretion half-life of about 3-6 hours.

In the study performed with the two stereoisomeric test substances urine was collected at 6, 12, 24 h and subsequently in 24 h intervals up to 72 h after treatment. The mean nominal doses of the test substances administered to the animals was 523.5 mg/kg bw for L- test substance and 512.5 mg/kg bw for D- test substance. 72 h after application of L-test substance 36.82 % of the dose was detected in urine whereof 90 % were excreted within the first 12 h. Based on the assumption that the amount of test substance excreted in urine correlates to the bioavailability the absorption of L- test substance was 36.82 % of the dose. A similar observation was made for D- test substance which was excreted to 93 % after 12 h and after 72 h 38.74 % of the administered dose was found in urine.

After single oral administration of L-test substance or D-test substance both test animal groups showed a comparable level of rapid absorption and rapid renal excretion of the test substances. Based on the test results and, it can be concluded that L-test substance and D-test substance both have no bioaccumulation potential. As a key value for risk assessment the mean oral absorption of 37.78 %, calculated from the mean oral absorptions of L- and D- test substance, was used.