A graphical nomogram method for predicting toxic concentrations of unbound phenytoin.
The graphical nomogram method to estimate the phenytoin free concentration at any selected total serum phenytoin and/or albumin concentrations was applied using Scatchard binding equation. The binding parameters were calculated by the non-linear least-squares regression analysis of the binding data collected from 96 outpatients on common anticonvulsant therapy. Free phenytoin concentration was measured by the Amicon multi-micro ultrafiltration system. The mean values of N and Kapp were found to be: N = 1.03, and Kapp = 18,500 (M-1). Correlation coefficient for relationship between measured and predicted free phenytoin concentrations was very good (r = 0.94), but the results of prediction-error analysis (MPE = 0.153, and RMSE = 0.296) show that the nomogram method overpredicts the measured free phenytoin (PHT) concentration approximately about 10% higher (15-30 mg/l) than serum phenytoin levels.
Pospisil
J
J
Department of Clinical Pharmacology, Charles University of Prague, Czech Republic.
Pelclová
D
D
D000328:Adult; D062787:Drug Overdose; D006801:Humans; D008875:Middle Aged; D010672:Phenytoin / Q000097:blood* / Q000506:poisoning; D011237:Predictive Value of Tests; D011485:Protein Binding; D012709:Serum Albumin / Q000378:metabolism*
D012709:Serum Albumin; D010672:Phenytoin