RESUMO
The treatment plan for chronic pain often proceeds from a single drug to drug combination therapy. Sinomenine and ligustrazine, natural alkaline substances derived from traditional Chinese medicines, are expected to provide a new choice for combination analgesic therapy strategies. Here we establish a microdialysis sampling and HPLC-MS/MS quantification method for sinomenine, ligustrazine, gabapentin, paracetamol, pregabalin and amitriptyline in rat blood and brain extracellular fluid. Blood and brain microdialysis probes were implanted in the jugular vein toward the right atrium and left corpus striatum zone (AP +0.2 mm, ML 3.0 mm, DV 3.5 mm) in rats. The blood and brain microdialysis probes were perfused with citric acid buffer solution and Ringer's solution, respectively. Blood and brain extracellular fluid microdialysate were collected at intervals of 20 min at a perfusion rate of 1.5 μL·min-1, and continuously collected for 24 h after administration. The liquid chromatographic separation used a C18-reversed phase chromatographic column (HSS T3 2.5 μm, 2.1 mm×50 mm), the mobile phase was methanol/water (containing 0.05‰ formic acid), and gradient elution was carried out at a flow rate of 0.3 mL·min-1. Mass spectrometric detection used an electrospray ion source, positive ion mode and multi-reaction monitoring method. The selected quantitative ions for sinomenine, ligustrazine, gabapentin, paracetamol, pregabalin, amitriptyline and internal standard naloxone were 330/181, 137/80, 172/154, 152/110, 160/142, 278/233 and 328/310 respectively. The specificity, linear range, matrix effect, accuracy, precision, stability and probe recovery were investigated and confirmed to be suitable for the determination of the above drugs in rat blood and brain extracellular fluid microdialysate. The calculated in vivo recovery of microdialysis probes ranged from 19.38% to 25.88%. After intravenous administration of sinomenine (50 mg·kg-1), ligustrazine (50 mg·kg-1), gabapentin (50 mg·kg-1), paracetamol (50 mg·kg-1), pregabalin (50 mg·kg-1) and amitriptyline (40 mg·kg-1) to rats, the peak concentration in the blood microdialysate was in the range of 0.2-10 μg·mL-1. Drug concentrations could also be detected in brain extracellular fluid microdialysate, however with lower levels (peak concentration: 0.1-6 μg·mL-1) than those of blood microdialysates at each time point. In conclusion, this method can be applied to microdialysis sampling and quantification of sinomenine, ligustrazine, gabapentin, paracetamol, pregabalin and amitriptyline in rats. The method will promote research in identifying herb-drug pharmacokinetic interactions, as well as safety concerns in combination-therapy strategies.