PT  - JOURNAL ARTICLE
AU  - Sirgo, Mark A.
AU  - Green, Paul J.
AU  - Rocci, Mario L.
AU  - Vlasses, Peter H.
TI  - Interpretation of serum phenytoin concentrations in uremia is assay‐dependent
AID  - 10.1212/WNL.34.9.1250
DP  - 1984 Sep 01
TA  - Neurology
PG  - 1250--1250
VI  - 34
IP  - 9
4099  - http://n.neurology.org/content/34/9/1250.short
4100  - http://n.neurology.org/content/34/9/1250.full
SO  - Neurology1984 Sep 01; 34
AB  - A 25-year-old man with sickle cell disease and chronic renal insufficiency had tonic-clonic seizures treated with phenytoin. Serum phenytoin concentrations, total and free, measured by two homogenous enzyme immunoassays (EMIT®, ACA®) were reported to be within the therapeutic range, yet the patient experienced seizures. Values on discharge exceeded the therapeutic range but were not associated with signs or symptoms of toxicity. Reanalysis of serum samples by a more specific, high performance liquid chromatographic (HPLC) method revealed the previous values were spurious, apparently due to phenytoin metabolite cross-reactivity. Values by fluorescence polarization immunoassay (TDX®,) correlated well with those by HPLC, as well as with the patient's clinical course.