Levothyroxine synthesis impurities are neither mutagenic nor genotoxic: Insilico, Ames test and micronucleus test studies.

In vitro and in silico tests were used to assess the possible genotoxicity and mutagenicity of five impurities that may be present in levothyroxine, a drug used for thyroid hormone replacement therapy. Neither ToxTree nor VEGA (Virtual Models for evaluating the properties of chemicals within a global architecture) identified cause for concern for any of the impurities. Ames test results (doses up to 1 mg per plate), with or without metabolic activation, were negative. The micronucleus test with TK6 (human lymphoblastoid) cells, at doses up to 500 µg/mL, with or without metabolic activation, also gave negative results.