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Description of key information

Key value for chemical safety assessment

Bioaccumulation potential:
low bioaccumulation potential

Additional information

To determine the systemic availability and the pharmacokinetics of thymol after oral application to humans, a clinical trial was carried out in 12 healthy volunteers. Each subject received a single dose of a Bronchipret® TP tablet, which is equivalent to 1.08 mg thymol. No thymol could be detected in plasma or urine. However, the metabolites thymol sulfate and thymol glucuronide were found in urine

and identified by LC-MS/MS. Plasma and urine samples were analyzed after enzymatic hydrolysis of the metabolites. Thymol sulfate, but not thymol glucuronide, was detectable in plasma. Peak plasma concentrations were 93.1 ± 24.5 ng/ml and were reached after 2.0 ± 0.8 hours. The mean terminal elimination half-life was 10.2 hours.

In another trial male Wistar rats received 1 mmol/kg bw (150 mg/kg bw) thymol by stomach tube.The urinary excretion was very rapid. Only very small amounts were excreted after 24 hrs. Although large quantities of thymol were excreted unchanged (or as their glucuronide and sulphate conjugates) extensive oxidation of the methyl and isopropyl group also occurred. This resulted in the formation of derivatives of benzyl alcohol and 2-phenylpropanol and their corresponding carboxylic acid.
Ring hydroxylation was a minor reaction. Based on these study results no bioaccumulation potential is expected.