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COMPARISON OF SINGLE‐POINT PHENYTOIN DOSAGE PREDICTION TECHNIQUES
Author(s) -
Yukawa E.,
Higuchi S.,
Ohtsubo K.,
Aoyama T.
Publication year - 1988
Publication title -
journal of clinical pharmacy and therapeutics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.622
H-Index - 73
eISSN - 1365-2710
pISSN - 0269-4727
DOI - 10.1111/j.1365-2710.1988.tb00196.x
Subject(s) - nomogram , phenytoin , mean squared error , mathematics , anticonvulsant , population , root mean square , chemistry , medicine , statistics , epilepsy , physics , environmental health , psychiatry , quantum mechanics
Summary To dose the anticonvulsant phenytoin (PHT) in a clinical situation is difficult because of the non‐linear metabolism of the drug. Therefore many techniques have been advocated to aid dosage adjustments based on a single‐point PHT concentration determined at steady‐state ( ss ). We retrospectively investigated six methods in a population of 130 out‐patients treated with PHT. The dose needed to achieve a desired PHT concentration at ss was calculated based on an observed 55 dose‐concentration pair using a Bayesian feedback method (B), the Richens and Dunlop nomogram (RD), the Rambeck nomogram (R), the Martin nomogram (M), a population clearance equation (PC), and the Wagner equation (W). The mean prediction error ( ME ), mean absolute error ( MAE ), and root mean squared error ( RMSE ) were separately calculated for each method, and served as a measure of prediction bias and precision. The MEs for B, RD, R, M, PC, and W, respectively, were ‐0·4, 1·2, 6·9, 3·4, ‐1·8, and 0·0 mg/day. The MAEs were 33·9, 38·5, 44·3, 50·4, 43·5, and 53·7 mg/day. The RMSE s were 43·7, 53·1, 65·2, 63·5, 56·0, and 68·2 mg/day. The MAE and RMSE showed lowest values for method B, followed by method RD. Therefore, we assume that method B is the most accurate in making routine PHT dosage adjustments.