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G J Yuen

Publications and source records attributed to G J Yuen.

22 records · Page 2Linked to original sources
PubMed1983

Predicting phenytoin dosages using Bayesian feedback: a comparison with other methods.

A Bayesian feedback technique for predicting phenytoin dosage was compared to other dosing methods. Sixty-nine cases were selected on the basis of apparent reliability from 103 medical charts of epileptic patients with multiple phenytoin levels on different dosage regimens. Two published nomograms and a graphical, or computational, technique were compared to the Bayesian technique. Each method was assessed for absolute predictability using measures of bias and precision, i.e., mean percent error and root mean squared percent error, respectively. For a single previous data pair, the Bayesian method was similar to a published nomogram with regard to bias and precision. For multiple data pairs, the graphical or simultaneous equation technique tended to be less biased, but the Bayesian method had better precision. However, none of these differences was statistically significant (p greater than 0.05). The Bayesian method yielded the lowest percentage of predicted doses that exceeded 110% of the actual dose. The Bayesian method conveniently provides a single method applicable to the use of either single or multiple concentration-dosage data pairs and results in fewer extreme dosing errors.

Adult↗
PubMed1983

Phenytoin cumulation profiles.

his study was performed to determine the potential utility of the cumulation profile of phenytoin during multiple oral dosing and to examine, under ideal conditions, the variability in apparent steady state concentrations. Six male subjects were administered oral phenytoin sodium 5-6 mg/kg/d in divided doses every 12h for six days. Predose serum phenytoin concentrations were measured every 12 hours by gas liquid chromatography. The resulting data were analyzed in order to estimate maintenance doses. Subjects were then placed on the estimated daily dose and pre-dose concentrations measured daily for at least two weeks. At the end of the study, all data were fit using non-linear regression analysis to obtain the best estimates of individual kinetic parameters. Parameter values, particularly the Km value, were dependent upon the input function used, either first- or zero-order. In two subjects there was evidence of modest auto-induction. At steady-state the average coefficient of variation of predose concentrations was 10.6% (Range: 5.2-16.2%).

Administration, Oral↗