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PetDosageChart

Luminal (Phenobarbital) Dosage for Dogs

Barbiturate anticonvulsant ⏱ Onset: 1-2 weeks for full seizure control ⏳ Duration: 12 hours per dose

This dosage information is for educational purposes only. Always consult your veterinarian before giving any medication to your pet. Dosages may vary based on your pet's health conditions, other medications, and individual factors.

Content reviewed by licensed veterinarians. This information is sourced from veterinary drug references including Plumb's Veterinary Drug Handbook and the Merck Veterinary Manual.

Dosage Calculator

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Luminal Dosage Chart for Dogs by Weight

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Weight Low Dose Standard Dose Max Dose Frequency
5 lbs (2.3 kg) 4.5mg 7mg 11.5mg (15mg tablet) Every 12 hours
10 lbs (4.5 kg) 9mg 13.5mg (15mg tablet) 22.5mg Every 12 hours
15 lbs (6.8 kg) 13.5mg (15mg tablet) 20.5mg 34mg Every 12 hours
20 lbs (9.1 kg) 18mg (15mg tablet) 27.5mg (2 × 15mg) 45.5mg (3 × 15mg) Every 12 hours
25 lbs (11.3 kg) 22.5mg 34mg 56.5mg (4 × 15mg) Every 12 hours
30 lbs (13.6 kg) 27mg (2 × 15mg) 41mg 68mg Every 12 hours
40 lbs (18.1 kg) 36mg 54.5mg 90.5mg (6 × 15mg) Every 12 hours
50 lbs (22.7 kg) 45.5mg (3 × 15mg) 68mg 113.5mg Every 12 hours
60 lbs (27.2 kg) 54.5mg 81.5mg 136mg (9 × 15mg) Every 12 hours
70 lbs (31.7 kg) 63.5mg (4 × 15mg) 95mg 158.5mg Every 12 hours
80 lbs (36.3 kg) 72.5mg (5 × 15mg) 109mg 181.5mg (12 × 15mg) Every 12 hours
90 lbs (40.8 kg) 81.5mg 122.5mg (8 × 15mg) 204mg Every 12 hours
100 lbs (45.4 kg) 91mg (6 × 15mg) 136mg (9 × 15mg) 227mg (15 × 15mg) Every 12 hours
120 lbs (54.4 kg) 109mg 163mg (11 × 15mg) 272mg (18 × 15mg) Every 12 hours
150 lbs (68 kg) 136mg (9 × 15mg) 204mg 340mg Every 12 hours

What is Luminal (Phenobarbital) used for in dogs?

Epilepsy Seizure disorders Status epilepticus management

How to give Luminal to your dog

Give phenobarbital tablets by mouth with food to reduce stomach upset. Administer at the same times every day, approximately 12 hours apart, to maintain stable blood levels. Do not crush or break tablets unless directed by your veterinarian. If using the oral liquid, shake well and measure with a syringe. Never skip or abruptly stop this medication without veterinary guidance.

Available Forms

Tablet, Oral liquid, Injectable

Give with Food?

Yes — give with food

Side effects of Luminal in dogs

Common side effects

Increased thirst and urination
Increased appetite and weight gain
Sedation and lethargy
Hind limb weakness or ataxia

Serious side effects

  • Liver toxicity with long-term use
  • Blood dyscrasias (anemia, low platelets)
  • Severe sedation or stupor
  • Paradoxical excitability
  • Pancreatitis

When to call the vet

Call your vet immediately if your dog shows any of these signs:

  • Seizures increase in frequency or severity
  • Yellowing of the gums, eyes, or skin (jaundice)
  • Severe sedation, inability to stand, or loss of coordination
  • Loss of appetite, vomiting, or diarrhea lasting more than 24 hours
  • Unusual bleeding or bruising

Related Medications for Dogs

Anticonvulsant

Keppra

Levetiracetam

For Epilepsy

View dosage chart
Anticonvulsant / Analgesic

Neurontin

Gabapentin

For chronic pain

View dosage chart
Antihistamine

Benadryl

Diphenhydramine

For allergies

View dosage chart
Serotonin antagonist and reuptake inhibitor (SARI)

Desyrel

Trazodone

For anxiety

View dosage chart

Sources & References

The dosage information on this page is compiled from the following veterinary and pharmaceutical references:

  • Plumb's Veterinary Drug Handbook — the standard veterinary pharmacology reference used by veterinarians worldwide.
  • Merck Veterinary Manual — a trusted, peer-reviewed resource for veterinary professionals and pet owners.
  • DailyMed (FDA Drug Labels) — official FDA-approved drug labeling and prescribing information for Phenobarbital.

Frequently Asked Questions

How long does a dog need to take phenobarbital?
Most dogs with epilepsy require lifelong phenobarbital therapy. Stopping the medication abruptly can trigger severe rebound seizures or status epilepticus, which is life-threatening. Your veterinarian may adjust the dose over time based on blood level monitoring, but discontinuation is rarely recommended.
What blood tests are needed for dogs on phenobarbital?
Dogs on phenobarbital need regular blood work including serum phenobarbital levels (checked 2-4 weeks after starting, then every 6 months), a complete blood count, and a liver chemistry panel. Liver enzymes should be monitored every 6-12 months since long-term use can cause hepatotoxicity.
Why is my dog so hungry and thirsty on phenobarbital?
Increased appetite (polyphagia), thirst (polydipsia), and urination (polyuria) are very common side effects of phenobarbital. These occur because the drug affects the brain centers that regulate hunger and thirst. Weight management through controlled feeding is important to prevent obesity.
Can phenobarbital cause liver damage in dogs?
Yes, long-term phenobarbital use can cause liver toxicity in some dogs. Signs include jaundice, loss of appetite, vomiting, and fluid accumulation in the abdomen. Regular liver enzyme monitoring helps detect problems early. If liver values become significantly elevated, your vet may switch to an alternative anticonvulsant.
What happens if I miss a dose of phenobarbital for my dog?
Give the missed dose as soon as you remember, unless it is nearly time for the next dose. Never double up. Missing doses can lower blood levels and trigger breakthrough seizures. Consistent twice-daily dosing at the same times is critical for maintaining therapeutic blood levels.

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