Abstract: AIM: To observe the influence of thyroid function on metabolism of diazepam and nordiazepam in rats.METHODS: HPLC method was used to determine the blood concentrations of diazepam and nordiazepam from rats with different thyroid function.RESULTS: Diazepam was metabolized rapidly in the rats with hyperthyroidism,the Cmax and AUC were decreased,and the T_1/2was cut short,but it showed an opposite results in the rats with hypothyroidism.WhilePharmacokineticParameters of diazepam were opposite in comparison with nordiazepam.CONCLUSION: Metabolism of diazepam increases in rats with hyperthyroidism.

Key words: pharmacokinetics, thyroid, diazepam, nordiazepam, drug metabolism