title: Plasma total phenytoin: a possibly misleading test in developing countries.
abstract: The use of phenytoin has increased among the rural black population in South Africa, many of whom have albumin concentrations below the accepted reference range of 35-50 g/L, related to a combination of malnutrition and late-presenting renal and hepatic disease. Because albumin concentration has a major effect on the proportion of free phenytoin in the extracellular fluid, we instituted a study of the extent of hypoalbuminemia and of the difference between "total" phenytoin (measured by immunoassay), and "corrected" phenytoin (calculated using the Sheiner-Tozer equation, which is based on a mean albumin of 40 g/L). The differences were significant (higher than 20%) in 37% of patients and led us to propose that in populations in which there is a high proportion of patients who are hypoalbuminemic, it is corrected rather than total phenytoin that should be the value reported.
authors.affiliation: Department of Chemical Pathology, SAIMR and the University of the Witwatersrand Medical School, Gauteng, South Africa.
authors.forename: C
authors.initials: C
authors.lastname: Fedler
authors.forename: M J
authors.initials: MJ
authors.lastname: Stewart
mesh_terms: D000927:Anticonvulsants / Q000097:blood* / Q000493:pharmacokinetics; D003906:Developing Countries; D016903:Drug Monitoring / Q000706:statistics & numerical data*; D006801:Humans; D009748:Nutrition Disorders / Q000097:blood; D010672:Phenytoin / Q000097:blood* / Q000493:pharmacokinetics; D011485:Protein Binding; D012709:Serum Albumin / Q000378:metabolism*; D013019:South Africa
chemical_list: D000927:Anticonvulsants; D012709:Serum Albumin; D010672:Phenytoin