Relationship between MPA free fraction and free MPAG concentrations in heart transplant recipients based on simultaneous HPLC quantification of the target compounds in human plasma

A simple and sensitive HPLC method for the simultaneous analysis of free MPA and free MPAG was developed. Separation was achieved on a X-Terra RP18 column with acetonitrile–40 mM orthophosphoric acid as eluents using a gradient elution mode over 35 min at a flow rate of 1.5 ml/min. The assay was linear in the range 0.005 mg/L (LOQ) to 5 mg/L for free MPA and 0.05 mg/L (LOQ) to 200 mg/L for free MPAG. Isolation of free MPA and free MPAG was done by ultrafiltration and the ultrafiltrate was directly injected. A positive correlation between MPA free fractions and free MPAG concentrations was found. Likewise, free MPAG was related to total MPAG concentrations in the seven heart transplant patients.