Rapid and slow release phenytoin in epileptic patients at steady state: Assessment of relative bioavailability utilizing Michaelis-Menten parameters

Ronald J. Sawchuk, Steven M. Pepin, Ilo E. Leppik, Robert J. Gumnit

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

The bioavailability of phenytoin from rapid release capsule and oral solution formulations relative to that of a slow release capsule formulation was assessed in five patients who had participated in a three-way crossover study performed at steady state. The subjects then underwent dosage adjustment utilizing the slow release formulation, and estimates of their Michaelis-Menten parameters thus obtained were utilized in calculating the relative bioavailabilities. In addition, expected changes in steady-state plasma phenytoin concentrations were calculated assuming initial levels of 15 mg/liter, with increases and decreases in bioavailability of 10%. The consequences of such alterations in the extent of phenytoin absorption or average content of the dosage form may be clinically significant, particularly where the initial phenytoin level is equal to or greater than the patient's operative Km.

Original languageEnglish (US)
Pages (from-to)383-391
Number of pages9
JournalJournal of Pharmacokinetics and Biopharmaceutics
Volume10
Issue number4
DOIs
StatePublished - Aug 1 1982

Keywords

  • Michaelis-Menten parameters
  • bioavailability
  • phenytoin

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