Evaluation of a Nomogram for Estimating the Rate of Phenytoin Accumulation

Levine, Marc; Orr, James; Chang, Tom

doi:10.1097/00007691-198706000-00007

Cited by 4 publications

(2 citation statements)

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“…When necessary the time to reach steady‐state was calculated. A few days to a week were allowed between the calculated time taken to reach steady state (8) and the blood collection to ensure that a steady state had been achieved. Total serum phenytoin concentrations were measured with a fluorescent polarization immunoassay using an automated TDxFLx R system (Abbott Laboratories, Diagnostic Division, North Chicago).…”

Section: Methodsmentioning

confidence: 99%

Optimization of phenytoin therapy in adults with epilepsy in the Western Cape, South Africa

Valodia

Seymour²,

Kies

et al. 1999

J Clin Pharm Ther

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Section: Methodsmentioning

confidence: 99%

Optimization of phenytoin therapy in adults with epilepsy in the Western Cape, South Africa

Valodia

Seymour²,

Kies

et al. 1999

J Clin Pharm Ther

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“…Levine et al (1987) evaluated the nomogram proposed by Vozeh and Follath (1980) as an aid in the dosing of phenytoin in patients who are near steady-state after beginning treatment. This was not a comparative trial, but rather the evaluation of an earlier nomogram.…”

Section: Pharmacokinetics-based Dosing Methodsmentioning

confidence: 99%

An Updated Comparison of Drug Dosing Methods

Pryka

Rodvold²,

Erdman³

1991

Clinical Pharmacokinetics

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The relationship between a dose of phenytoin and the resultant serum concentration is difficult to predict, and numerous dosing methods have been developed to quantify the dose required to achieve a specific concentration. This review brings up to date the earlier article in the Journal regarding predictive algorithms, various pharmacokinetics-based dosing techniques and Bayesian feedback methods for phenytoin dosing. The latest data support the original conclusions that dosing methods for phenytoin which incorporate an individualised approach or Bayesian principles tend to offer results superior to those from predictive algorithms. Bayesian methods have the additional advantage of using only 1 serum concentration, obtained under either steady-state or non-steady-state conditions. There is still a need for future investigations that include prospective evaluations of predictive performance and cost-effectiveness data.

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Therapeutic Drug Monitoring of Phenytoin Rationale and Current Status

Levine

Chang

1990

Clinical Pharmacokinetics

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The rationale fo r measuring serum drug concentrations as a guide to therapy is based on 2 assumptions: that there is a direct relationshi p between the drug concentra tion in serum and the concentration of the free drug at the receptor site. and that this de term ines the therapeutic effect (Koch-Weser 1975). This has evolved to the curre nt target concentra tion st rategy (Sheiner & Tozer 1978: Spector et a1. 1988) in which dosage adjustments are made to bring patients' serum drug concen trations into t he ta rge t or "therapeutic' ra nge. Concentrations below or above this range are considered to be ei ther ·subtherapeutic' or ·toxic'. respectively. Recently. Spector et a1. (1988) have questioned the val ue of routine therapeutic drug monitoring in generaL citing the aminoglycosides and digoxin as specific exam ples.It has been argued that therapeutic drug monito ri ng of phenytoin is panicularly justifiable because of its narrow therapeutic range and saturable eli minat ion kinetics (Morrow & Richens 1989: Perrucca & Richens 198I a). The clinical pharmacoki netics of phenytoi n are well known. and have been reviewed b y o t hers (Mani n et a1. 1977: Richens 1979: Winter & Tozer 1986). During the past 10 yea rs. therapeutic d rug monitoring of phenytoin has become rout ine i n the management of patients with epilepsy_ The therapeutic range is generally considered t o be 40 to 80 ~mol / L. and many clinicians employ the target concent ration strategy to individualise their patients· dosages. This anicle crit ically examines the basis fo r therapeutic mon ito ring of phenytoin and the appropriateness of the target concentration strategy. It considers the pharmacokinet ic methods available for the individualisation of phenytoin dosage and, in panicular. the potential advan tagt!s of Bayesian forecasting. It also exam ines the stat us o f the debate whether free or tOlal phenytoin concentration should be monitored. Finally, the authors consider the evidence for the cli nical utility of therapeutic monitori ng of phenytoin. and the need fo r fut ure research.

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Evaluation of a Nomogram for Estimating the Rate of Phenytoin Accumulation

Cited by 4 publications

References 0 publications

Optimization of phenytoin therapy in adults with epilepsy in the Western Cape, South Africa

Optimization of phenytoin therapy in adults with epilepsy in the Western Cape, South Africa

An Updated Comparison of Drug Dosing Methods

Therapeutic Drug Monitoring of Phenytoin Rationale and Current Status

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