Abstract: AIM: To investigate the pharmacokinetics of minocycline in rat blood and brain. METHODS: Microdialysis technique and HPLC were used to determine the plasma protein binding rate of minocylcine, and the concentrations of free minocycline in the blood and hippocampal CA1 region were determined at different intervals in 10 hours after the rat was received a single injection of minocycline via tail vein. RESULTS: The rat plasma protein binding rate of minocycline is 82.08%.Minocycline crossed the blood-brain barrier rapidly, and the concentration reached its peak (t_max) in 3.83 hours after injection, and then dropped slowly.The ratio of area under the curve (AUC_{0-10 h}) in the brain to that in the blood is up to 62.42%. CONCLUSION: Microdialysis technique combined with HPLC could be utilized to successfully determine the rat plasma protein binding rate of minocycline, and to achieve dynamic monitoring of the free minocycline concentration in rat blood and brain.The results suggest that minocycline could easily across the blood-brain barrier and maintained its concentration at a high level for a long time, thus playing its neuroprotective role.

Key words: Minocycline, Pharmacokinetics, Plasma protein binding rate, Microdialysis, HPLC