Plasma concentrations and relative bioavailability of naftidrofuryl from different salt forms

The relative bioavailability of the vasodilator naftidrofuryl from formulations containing its oxalate or citrate salt has been estimated using a specific HPLC assay, and a less specific fluorimetric assay, to measure plasma drug concentrations. The conclusions of the study were the same irrespective of the assay employed. The relative rate, but not the extent, of bioavailability of naftidrofuryl from the citrate salt (peak 1096 ng ml−1 at 0·76 h) was marginally greater (p = 0·003) than that from the oxalate salt (peak 922ng ml−1 at 0·94 h). The degree of intersubject variability was similar after administration of either salt form. The mean half‐life of naftidrofuryl was 1·8 h and its mean residence time was 2·5 h.