A simple blood microdialysis in freely-moving rats for pharmacokinetic–pharmacodynamic modeling study of Shengmai injection with simultaneous determination of drug concentrations and efficacy levels in dialysate

[Display omitted] •A simple blood microdialysis system in freely-moving rats was established.•Simultaneous determination of drug concentrations and efficacy levels in dialysate for the PK-PD modeling study.•A LC–MS/MS method was developed to simultaneously determine seven components of Shengmai injection in blood dialysates.•The established PK-PD modeling of Shengmai injection characterized the dose-effect relationship of the drug. Microdialysis is a powerful in vivo sampling technique for pharmacokinetic–pharmacodynamic (PK-PD) modeling of drugs in pre-clinical and clinical studies. However, the noticeable limitations of previous studies using microdialysis were that animals anesthesia in the whole experiment and the combination of microdialysis and blood sampling for drug and (or) effect detection, which can obviously influence PK and PD behavior of drugs. In this study, a simple blood microdialysis sampling system in freely-moving rats was established for simultaneous study of PK and PD of Shengmai injection (SMI) effect on inducing real-time nitric oxide (NO) release on isoproterenol (ISO) induced myocardial ischemia rats. The LC–MS/MS and HPLC with fluorescence detection (HPLC-FLD) methods were developed to determine ginsenside Rg1, Rg2, Re, Rf, Rb1, Rd and Rc, the main effective components of SMI, and NOx−, the main oxidation products of NO, in dialysates respectively. Through simultaneous determination of drug concentrations and NO efficacy levels in dialysate, the developed methods were successfully applied to set up concentration-time and effect-time profiles followed by PK-PD modeling of SMI effect on inducing NO release after intravenous administration of 10.8 mL kg−1 SMI in myocardial ischemia rats. The PK-PD modeling characterized the dose-effect relationships of SMI and behaved good prediction ability. The established blood microdialysis in freely-moving rats is an appealing technology for rational PK-PD studies when selecting suitable blood endogenous micromolecule as effect marker.