Development of a sensitive enzyme immunoassay for OPC-7251, a novel antimicrobial agent for percutaneous application.

A sensitive enzyme immunoassay for OPC-7251, a novel pyridone carboxylic acid antimicrobial agent, was developed and applied for the determination of human plasma levels. OPC-7251 was coupled to bovine serum albumin through a formation of N-hydroxysuccinimide ester. By immunization of rabbits, highly specific antiserum was raised. Using the antiserum and beta-D-galactosidase-labeled hapten, the homologous assay system allowed the detection of 2 pg of this compound. Plasma samples were precisely analyzed down to the minimum value of 200 pg/ml after heat treatment. The system was further validated by the recovery test and correlation with the HPLC analyses. Percutaneous application of 10 g of 1% OPC-7251 cream to healthy volunteers resulted in the peak plasma value of 1.6 ng/ml about 8 hours after dosing, indicating extremely low absorption efficiency through a transdermal system.