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Bioavailability and pharmacokinetics of phenytoin during pregnancy

European Journal of Clinical Pharmacology volume 27, pages 105–110 (1984)Cite this article

Summary

Five epileptic women needing to commence phenytoin therapy during pregnancy received a single intravenous and a single oral dose of phenytoin several days apart before starting regular intake of the drug. Plasma phenytoin concentration — time data were analysed by three different pharmacokinetic techniques. However assessed, the mean oral bioavailability of the drug proved to be about 90% of the intravenous bioavailability. This finding makes it unlikely that impaired bioavailability accounts for the increase in oral phenytoin dosage necessary in pregnancy to maintain plasma phenytoin concentrations at pre-pregnancy values. Phenytoin clearance in the pregnant subjects was approximately double the published values for phenytoin clearance in nonpregnant persons. This suggests that increased (metabolic) clearance accounts for the increased phenytoin dosage requirement of pregnancy.

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Authors and Affiliations

  1. Department of Medicine, University of Queensland, and Royal Women’s Hospital, Brisbane, Australia

    C. M. Lander, M. T. Smith, J. B. Chalk, C. de Wytt, P. Symoniw, I. Livingstone & M. J. Eadie

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  1. C. M. Lander
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  2. M. T. Smith
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  3. J. B. Chalk
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  4. C. de Wytt
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  5. P. Symoniw
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  6. I. Livingstone
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  7. M. J. Eadie
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Lander, C.M., Smith, M.T., Chalk, J.B. et al. Bioavailability and pharmacokinetics of phenytoin during pregnancy. Eur J Clin Pharmacol 27, 105–110 (1984). https://doi.org/10.1007/BF02395215

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  • DOI: https://doi.org/10.1007/BF02395215

Key words

  • phenytoin
  • epileptic women
  • pharmacokinetics
  • bioavailability
  • pregnancy