Felis ISSN 2398-2950

Phenytoin

Contributor(s): Kyle Braund

Introduction

Name

  • Phenytoin sodium.

Class of drug

  • Anti-epileptic.

Uses

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Indications

  • It is used to control most forms of epilepsy   Epilepsy: idiopathic  in human medicine.
  • Metabolized very rapidly in dogs such that very high doses need to be given often, whereas cats metabolize the drug very slowly and toxicity easily develops.
  • These undesirable pharmacokinetc properties make it a secondary agent in veterinary medicine.
  • Its use in the cat cannot be recommended.

Administration

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Pharmocokinetics

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Precautions

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Interactions

with other drugs

Many interactions are reported in the human literature. This list includes only those which may be of veterinary significance.Drugs increasing plasma concentration of phenytoin Drugs decreasing effect of phenytoin (absorption, effects or plasma concentration)
  • Antacids.
  • Antineoplastic drugs.
  • Barbiturates.
  • Calcium.
  • Nitrofurantoin   Nitrofurantoin  .
  • Pyridoxine.
Drugs affected by phenytoin (increased metabolism)
  • Corticosteroids.
  • Doxycycline.
  • Estrogens.
  • Theophylline   Theophylline  .
  • Thyroxine.
Pethidine
  • The analgesic properties may be reduced by phenytoin whereas the toxic effects may be enhanced
Anti-epileptics
  • Concomitant administration of 2 or more anticonvulsants may enhance toxicity without a corresponding increase in anti-epileptic effect.

Adverse Reactions

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Further Reading

Publications

Other sources of information

  • Based onSmall Animal Formulary.Tennant Bryn (1999) 3rd edn. Cheltenham: BSAVA.

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