Fluorescent immunoassay for determining antiepileptic drug concentrations: clinical usefulness

The need for rapid and accurate antiepileptic drug measurement in blood is well established. A substrate-labeled fluorescent immunoassay (FIA) has been developed that can measure phenobarbital, phenytoin, primidone, and carbamazepine in serum. To our knowledge, the primidone and carbamazepine assays have not previously been tested in a field trial. We compared FIA and the well-established antiepileptic drug immunoassay technique EMIT for the quantitation of both carbamazepine and primidone. In our hands, the FIA method compared favorably with the EMIT method for accuracy and reliability but is somewhat more time consuming. This method has the advantage of being more sensitive, however, and requires only a finger-stick blood sample. Because of this and the simplicity of the equipment required, the FIA system should also be relatively inexpensive to set up and to operate.