A Rate Nephelometric Phenobarbital and Phenytoin

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Abstract
A new single-point calibration immunoprecipitation inhibition rate nephelometric assay for [the anticonvulsants] phenobarbital (PB) and phenytoin (PT) [in human serum] was evaluated on the Beckman ICS[intercellular substance]-II analyzer. Within-run precision (n = 20) coefficients of variation (CV) were < 4.0% for PB (10-44 .mu.g/ml) and < 5.7% for PT (12-34 .mu.g/ml). Between-run precision CV of pooled sera (n = 20) assay was < 4.2% for PB (7.5-33.8 .mu.g/ml) and < 8.7% for PT (4.5-17.8 .mu.g/ml). Linearity and recoveries were good over a broad range of drug levels for both assays. Excellent correlation was found with existing PB, ICS vs. EMT [enzyme multiplied immunoassay technique] on the IL Multistat III MCA [micro centrifugal Analyzer] (y = 1.26 + 1.00x; r = 0.994), ICS vs. Dupont aca (y = 0.832 + 1.01x; r = 0.997), and ICS vs. GLC (y = 0.08 + 0.99x; r = 0.998) methods, and PT, ICS vs. MCA (y = -1.76 + 1.04x; r = 0.985), ICS vs. aca (y = -2.02 + 1.054x; r = 0.987), and ICS vs. GLC (y = -0.26 + 0.990x; r = 0.999) methods. These assays provided accurate drug analyses, good stat or batching capability, and good correlation with existing methods.