Measurement and pharmacokinetic study of tetramethylpyrazine in rat blood and its regional brain tissue by high-performance liquid chromatography.

We used a rapid, sensitive and reliable high-performance liquid chromatographic method for the determination of tetramethylpyrazine in rat brain tissue and plasma. The lower limit of quantification in plasma and brain tissue was 0.1 microgram/ml and 0.1 microgram/g, respectively, and only a small amount of plasma (100 microliters) or brain tissue (100 micrograms) was required for analysis. The decline in the concentration of tetramethylpyrazine in plasma was generally two-exponential at a dose of 2, 5, or 10 mg/kg administered intravenously. Concentrations of tetramethylpyrazine in various regions of the brain (cerebral cortex, brainstem, striatum, hippocampus, cerebellum and midbrain) were not significantly different at 15 min following drug administration (10 mg/kg, i.v.). In additional analysis, mean concentration of the tetramethylpyrazine in rat plasma was approximately five-times greater than the drug in brain tissue.