Exotis ISSN 2398-2985

Reptiles

Phenobarbital

Synonym(s): Epiphen, Phenobarbitone, Fenobarbital

Contributor(s): Vetstream Ltd, David Perpinan

Introduction

Name

  • Phenobarbital.
  • Phenobarbital sodium.

Class of drug

  • Anticonvulsant/antiepileptic.
  • Long-acting barbiturate.
  • Schedule IV controlled drug (non-narcotic basic class) and available by prescription only.

Description

Chemical name

  • 5-ethyl-5-phenyl-1,3-diazinane-2,4,6-trione.

Molecular formula

  • C12H12N2O3.

Molecular weight

  • 232.

Physical properties

  • White, odorless small crystals or crystalline powder.
  • One gram is soluble in 1 L of water and 10 mL of alcohol.
  • Phenobarbital sodium occurs as bitter-tasting, white, odorless, flaky crystals or crystalline granules or powder. Very soluble in water and soluble in alcohol.

Storage requirements

  • Store in tight, light-resistant containers or vials at room temperature.

Uses

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Indications

  • Uncommonly used in reptiles to manage seizures (idiopathic or toxic in origin).
  • Seizures caused by hypocalcemia or secondary hyperparathyroidism are not usually treated with phenobarbital.
  • Acute seizuring may be treated with phenobarbital if diazepam Diazepam/midazolam Midazolam are not available.

Administration

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Pharmacokinetics

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Precautions

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Interactions

with other drugs

  • Phenobarbital in reptiles increases activity of cytochrome P450.
Drugs increasing effect of phenobarbital
  • Chloramphenicol.
  • Central nervous system (CNS) depressants (antihistamines, narcotics, phenothiazines).
Drugs affected by phenobarbital (enhanced metabolism/decreased effect)
  • Corticosteroids.
  • Beta-blockers (propranolol).
  • Metronidazole.
  • Oral anticoagulants.
  • Quinidine.
  • Theophylline.
Griseofulvin
  • Phenobarbital may decrease absorption; avoid giving them together.
Anti-epileptics
  • Barbiturates may enhance the effect of other anti-epileptics.
  • Phenobarbital reduces total plasma benzodiazepine concentration.

Adverse Reactions

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Further Reading

Publications

Refereed papers

Other sources of information

  • Meredith A (2015) Ed BSAVA Small Animal Formulary. Part B: Exotic Pets. 9th edn. BSAVA, United Kingdom. pp 338.
  • Plumb D (2015) Plumb’s Veterinary Drug Handbook. 8th edn. Wiley Blackwell. pp 1296. 
  • Tennant B (1999) Small Animal Formulary. 3rd edn. BSAVA, Cheltenham, UK.

Organisation(s)

  • National Office of Animal Health (NOAH) Compendium of Data Sheets for Animal Medicines. Website: www.noahcompendium.co.uk.

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