Diclofenac in vitro microdialysis study comparing different experimental setups to improve quantitative recovery

LC-MS/MS combined with blood-brain dual channel microdialysis for simultaneous determination of active components of astragali radix-safflower combination and neurotransmitters in rats with cerebral ischemia reperfusion injury: Application in pharmacokinetic and pharmacodynamic study

BACKGROUND

Astragali Radix-Safflower combination (ARSC) is widely utilized in clinic to treat cerebral ischemia/reperfusion injury (CI/RI). Whereas, there is no in-depth research of the pharmacokinetics (PK) and pharmacodynamics (PD) analysis of ARSC after intragastric administration in rats with CI/RI.

PURPOSE

The purpose of this research is to investigate the PK characteristics of eight active ingredients (astragaloside IV, calycosin, calycosin-7-O-β-glucoside, formononetin, ononin, hydroxysafflor yellow A, syringin and vernine) of ARSC, and the regulation of neurotransmitters disorders, revealing the pharmacodynamic substance basis and the mechanism of ARSC in treating CI/RI from the molecular level.

METHODS

We established a new method which based on blood-brain dual channel microdialysis (MD) coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) to continuously gather, and determine the components of ARSC and neurotransmitters related to CI/RI in vivo. The collected data were analyzed by sigmoid-E_max function. The neurotransmitters primarily regulated in CI/RI rat were discussed by principal component analysis and the compound most associated with total pharmacodynamics was chosen by partial least squares regression.

RESULTS

The validated LC-MS/MS method had specificity and selectivity to simultaneously analyze the concentration of eight active components of ARSC extract and five neurotransmitters of CI/RI rats. The recovery rates of brain MD probe and blood MD probe were stable within six hours. The MD probes recovery rates decreased with the increase of flow rates, but the solution concentration had little effect on the probes recovery rates. It was feasible to correct the recovery rates of probes in vivo by using reverse dialysis method. All eight active ingredients of ARSC could pass across the blood brain barrier after CI/RI. ARSC regulated the release of glutamate (Glu), γ-aminobutyric acid (GABA), dopamine (DA), 5-hydroxytryptamine (5-HT) and aspartic acid (Asp). Notably, astragaloside IV and hydroxysafflor yellow A might have better regulatory effect on neurotransmitters in comparison with other six measured components of ARSC, and Glu was the neurotransmitter mainly regulated in CI/RI rats.

CONCLUSION

The ARSC was able to treat CI/RI through ameliorating neurotransmitters disorders. There was a hysteresis between the peaked drug concentration and maximum therapeutic effect of ARSC. The drug effective concentrations range of ASIV, calycosin, calycosin-7-O-β-glucoside, syringin and vernine in blood microdialysate and calycosin, syringin, vernine in brain microdialysate were narrow, which need be paid attention in clinical use.

Accelerator mass spectrometry for quantification of micro- and therapeutic dose diclofenac in microdialysis samples

Background: Microdialysis sampling after drug microdosing may provide tissue pharmacokinetic data early in clinical drug development. However, low administered doses and small sample volumes pose an analytical challenge, particularly for highly protein-bound drugs. Materials & methods: Carbon-14 [¹⁴C]diclofenac was used as a model drug to assess the technical and analytical feasibility of in vivo microdialysis after microdose administration in an in vitro setup. Results: [¹⁴C]diclofenac dialysate concentrations were accurately quantified with accelerator MS. [¹⁴C]diclofenac dialysate recoveries were similar in the presence and absence of therapeutic diclofenac concentrations but were considerably decreased when albumin was added to the immersion solution, suggesting high protein binding. Conclusion: These results demonstrate the feasibility of combining microdosing and microdialysis to assess tissue pharmacokinetics.