MDose · Veterinary drug reference
PHENOBARBITAL
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Source overview
Recorded excerpts for one species. Each dose remains a separate source entry; no regimen is selected.
Choose one species to view its source overview. All-species evidence remains available below.
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Pending clinical review (PROPOSED)Rule-based (RULE_BASED)— applies to the facts and dose entries in this species selection; individual source records retain their own status.
Indications2
Idiopathic epilepsy (first-line), status epilepticus, sedation
DogNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Dog · Plumb's Veterinary Drug Handbook, 7th ed., p. 958–961; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 624–626 — Indications table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Original excerpt: Idiopathic epilepsy (first-line), status epilepticus, sedation — Labeled (C-IV controlled)
- Dog · Plumb's Veterinary Drug Handbook, 7th ed., p. 958–961; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 624–626 — Indications table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Idiopathic epilepsy (drug of first choice), status epilepticus
CatNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Cat · Plumb's Veterinary Drug Handbook, 7th ed., p. 958–961; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 624–626 — Indications table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Original excerpt: Idiopathic epilepsy (drug of first choice), status epilepticus — Labeled
- Cat · Plumb's Veterinary Drug Handbook, 7th ed., p. 958–961; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 624–626 — Indications table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Dose regimens6
This calculator performs arithmetic only on the sourced dosing field shown for each result — it does not verify the field's accuracy, does not select which field to use for a patient, and does not replace a veterinarian's order. Not for clinical use. Confirm every result against the primary source before dispensing.
Choose one species above to view its dose calculator.
Adverse effects208
PU/PD/polyphagia, sedation, ataxia — Common, dose-related
DogCatNot applicable (NOT_APPLICABLE)2 source records · View provenance
- Dog · Plumb's Veterinary Drug Handbook, 7th ed., p. 958–961; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 624–626 — Side Effects / Adverse Effects table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
- Cat · Plumb's Veterinary Drug Handbook, 7th ed., p. 958–961; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 624–626 — Side Effects / Adverse Effects table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Elevated liver enzymes (ALP especially) — Common; not always hepatopathy
DogNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Dog · Plumb's Veterinary Drug Handbook, 7th ed., p. 958–961; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 624–626 — Side Effects / Adverse Effects table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Hepatotoxicity — Uncommon; more likely levels >30–40 mcg/mL
DogNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Dog · Plumb's Veterinary Drug Handbook, 7th ed., p. 958–961; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 624–626 — Side Effects / Adverse Effects table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Neutropenia, anemia, thrombocytopenia — Rare, idiosyncratic, reversible
DogNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Dog · Plumb's Veterinary Drug Handbook, 7th ed., p. 958–961; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 624–626 — Side Effects / Adverse Effects table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Superficial necrolytic dermatitis — Rare
DogNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Dog · Plumb's Veterinary Drug Handbook, 7th ed., p. 958–961; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 624–626 — Side Effects / Adverse Effects table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
These are counts of spontaneously reported events, not proven adverse effects, causal relationships, or incidence rates.
Bars compare report counts within each species; they do not show incidence.
More reportsFewer reportsDog
- Seizure NOS574 reports
- Lethargy (see also Central nervous system depression in 'Neurological')164 reports
- Vomiting153 reports
- Death by euthanasia102 reports
- Other abnormal test result NOS97 reports
- Lack of efficacy - NOS91 reports
- Ataxia85 reports
- Emesis85 reports
- Diarrhoea83 reports
- Death78 reports
- Elevated serum alkaline phosphatase (SAP)72 reports
- Anorexia69 reports
Cat
- Seizure NOS40 reports
- Death by euthanasia18 reports
- Lethargy (see also Central nervous system depression in 'Neurological')16 reports
- Twitching15 reports
- Behavioural disorder NOS14 reports
- Ataxia12 reports
- Vomiting11 reports
- Weight loss10 reports
- Emesis9 reports
- Not eating9 reports
- Anaemia NOS8 reports
- Weakness8 reports
Monitoring1
Serum phenobarbital levels 2–3 weeks after start/dose change: dog target ~15–35 mcg/mL, cat ~23–30 mcg/mL. CBC, chemistry (bile acids, albumin) periodically — watch hepatotoxicity as levels approach 30–35 mcg/mL.
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Plumb's Veterinary Drug Handbook, 7th ed., p. 958–961; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 624–626 — Monitoring Parameters · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Contraindications1
Known hypersensitivity, severe liver disease, nephritis or severe respiratory depression (large doses)
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Plumb's Veterinary Drug Handbook, 7th ed., p. 958–961; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 624–626 — Contraindications & Warnings table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Precautions4
Hypovolemia, anemia, borderline hypoadrenal function, cardiac/respiratory disease; give IV slowly (≤60 mg/min), never SC/perivascular (irritating/necrotic); pregnancy may increase seizure frequency
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Plumb's Veterinary Drug Handbook, 7th ed., p. 958–961; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 624–626 — Contraindications & Warnings table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Sample timing for serum levels is not time-critical relative to dose — draw any time during the interval.
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Plumb's Veterinary Drug Handbook, 7th ed., p. 958–961; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 624–626 — Clinical pearl · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Autoinduction of hepatic metabolism means dose requirements can drift upward over time even with stable seizure control — periodic rechecks are needed even in "stable" patients.
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Plumb's Veterinary Drug Handbook, 7th ed., p. 958–961; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 624–626 — Clinical pearl · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
C-IV controlled substance — standard controlled-drug logging/dispensing rules apply.
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Plumb's Veterinary Drug Handbook, 7th ed., p. 958–961; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 624–626 — Clinical pearl · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Interactions5
Levetiracetam — Phenobarbital ↓ levetiracetam half-life ~50% (dogs) — may need higher/more frequent dosing
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Plumb's Veterinary Drug Handbook, 7th ed., p. 958–961; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 624–626 — Drug Interactions table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Zonisamide — ↑ clearance, shortens zonisamide half-life — higher doses needed in combo
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Plumb's Veterinary Drug Handbook, 7th ed., p. 958–961; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 624–626 — Drug Interactions table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Chloramphenicol, cimetidine, azoles (itraconazole) — ↑ phenobarbital levels
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Plumb's Veterinary Drug Handbook, 7th ed., p. 958–961; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 624–626 — Drug Interactions table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Corticosteroids, cyclosporine, doxycycline, digoxin, theophylline, warfarin, beta-blockers — ↓ effect via induced hepatic clearance
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Plumb's Veterinary Drug Handbook, 7th ed., p. 958–961; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 624–626 — Drug Interactions table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
MAO inhibitors (amitraz, selegiline) — May prolong phenobarbital effects
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Plumb's Veterinary Drug Handbook, 7th ed., p. 958–961; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 624–626 — Drug Interactions table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Pharmacokinetics6
Bioavailability — ~90%
DogNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Dog · Plumb's Veterinary Drug Handbook, 7th ed., p. 958–961; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 624–626 — Pharmacokinetics table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Protein binding — 40–60%
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Plumb's Veterinary Drug Handbook, 7th ed., p. 958–961; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 624–626 — Pharmacokinetics table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Half-life — 12–125h (avg ~2 days), shortens with autoinduction; may drop <24h requiring TID dosing
DogCatNot applicable (NOT_APPLICABLE)2 source records · View provenance
- Dog · Plumb's Veterinary Drug Handbook, 7th ed., p. 958–961; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 624–626 — Pharmacokinetics table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
- Cat · Plumb's Veterinary Drug Handbook, 7th ed., p. 958–961; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 624–626 — Pharmacokinetics table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Metabolism — Hepatic, induces its own (and other drugs') CYP metabolism
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Plumb's Veterinary Drug Handbook, 7th ed., p. 958–961; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 624–626 — Pharmacokinetics table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Elimination — ~25% renal unchanged; rest hepatic metabolites
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Plumb's Veterinary Drug Handbook, 7th ed., p. 958–961; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 624–626 — Pharmacokinetics table · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Pregnancy / lactation considerations1
Human FDA category D. Papich canine/feline class B (safe if used cautiously/not near term). Excreted in milk — drowsiness reported in nursing offspring.
Species not recordedNot applicable (NOT_APPLICABLE)1 source record · View provenance
- Species not recorded · Plumb's Veterinary Drug Handbook, 7th ed., p. 958–961; Saunders Handbook of Veterinary Drugs (Papich), 4th ed., p. 624–626 — Pregnancy & Lactation · Not applicable · Not applicable (NOT_APPLICABLE) · Pending clinical review (PROPOSED) · Rule-based
Literature references11
References are linked to this drug. Species applicability is not recorded here, so the species filter does not narrow this list. Imported dates do not retain their original precision; confirm dates in the original citation.
- Antiseizure monotherapy with imepitoin or phenobarbital in feline idiopathic epilepsy: a multicenter, single-blinded, randomized and placebo-controlled study.
Study summary not available in the imported record. Open the original citation to review the study.
- Canine duodenal organoids as a functional platform for intestinal CYP regulation and drug metabolism studies.
Study summary not available in the imported record. Open the original citation to review the study.
- Pharmacometrics modeling and simulation to assist phenobarbital dose optimization in dogs.
Study summary not available in the imported record. Open the original citation to review the study.
- Effects of Phenobarbital and Prednisolone on Neurological Signs of Canine Distemper.
Study summary not available in the imported record. Open the original citation to review the study.
- MRI diagnostics and management of idiopathic epilepsy in ring-tailed lemur (Lemur catta).
Study summary not available in the imported record. Open the original citation to review the study.
Sources: PubMed, National Library of Medicine; openFDA, U.S. Food and Drug Administration; Plumb DC. Plumb's Veterinary Drug Handbook. 7th ed. PharmaVet Inc; 2011.
Owner information handout
Plain-language medication information to review with the owner. Open the handout to print it or download a PDF.
Available products
Products listed in the Health Canada Drug Product Database for this active ingredient. A listing does not establish that a product is authorized for the clinical uses described on this page.