POM-V
Prescription Required
Companion Animal
Epiphen 60 mg Tablets
Active ingredient: Phenobarbital
Form
Tablet
Species
Dogs
Manufacturer
Vetoquinol SA
VMD MA No.
06462/3008
What it's used for
Phenobarbital is an antiepileptic agent for use in the control of epilepsy in the dog.
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Clinical information
Epiphen 60 mg Tablets — SPC Details
Source: VMD Summary of Product Characteristics (SPC). Last updated 26 Mar 2026.
Phenobarbital is an antiepileptic agent for use in the control of epilepsy in the
dog.
dog.
The required dosage will differ to some extent between individuals and
with the nature and severity of the disorder.
Dogs should be dosed orally, starting with a dose of 2-5mg per kg bodyweight
per day. The dose should be divided and administered twice daily.
Steady state serum concentrations are not reached until 1-2 weeks after
treatment is initiated. The full effect of the medication does not appear for
two weeks and doses should not be increased during this time.
If seizures are not being controlled, the dosage may be increased by 20% at
a time, with associated monitoring of serum phenobarbital levels. The
phenobarbital serum concentration may be checked after steady state has
been achieved, and if it is less than 15 mg/l the dose may be adjusted
accordingly. If seizures recur the dose may be raised up to a maximum
serum concentration of 40 mg/l (see special precautions for use). High
plasma concentrations may be associated with hepatotoxicity. Blood
samples could be taken at the same time to allow plasma phenobarbital
concentration to be determined preferably during trough levels, shortly
before the next dose of phenobarbital is due.
For accuracy of dosing, dogs under 6 kg should commence therapy with
Epiphen solution, and dogs between 6 and 12 kg should commence therapy
with either Epiphen solution or Epiphen 30mg tablets.
Tablets can be divided into quarters to ensure accurate dosing. To break a
cross scored tablet into quarters, place the tablet on an even surface and
apply pressure on the middle with your thumb.
with the nature and severity of the disorder.
Dogs should be dosed orally, starting with a dose of 2-5mg per kg bodyweight
per day. The dose should be divided and administered twice daily.
Steady state serum concentrations are not reached until 1-2 weeks after
treatment is initiated. The full effect of the medication does not appear for
two weeks and doses should not be increased during this time.
If seizures are not being controlled, the dosage may be increased by 20% at
a time, with associated monitoring of serum phenobarbital levels. The
phenobarbital serum concentration may be checked after steady state has
been achieved, and if it is less than 15 mg/l the dose may be adjusted
accordingly. If seizures recur the dose may be raised up to a maximum
serum concentration of 40 mg/l (see special precautions for use). High
plasma concentrations may be associated with hepatotoxicity. Blood
samples could be taken at the same time to allow plasma phenobarbital
concentration to be determined preferably during trough levels, shortly
before the next dose of phenobarbital is due.
For accuracy of dosing, dogs under 6 kg should commence therapy with
Epiphen solution, and dogs between 6 and 12 kg should commence therapy
with either Epiphen solution or Epiphen 30mg tablets.
Tablets can be divided into quarters to ensure accurate dosing. To break a
cross scored tablet into quarters, place the tablet on an even surface and
apply pressure on the middle with your thumb.
Not for use in pregnant animals.
Do not administer to animals with impaired hepatic function.
Do not use in cases of hypersensitivity to the active substance(s), to any other
barbiturates or to any of the excipients
Do not use in animals with serious renal and/or cardiovascular/respiratory
disorders.
Do not administer to animals with impaired hepatic function.
Do not use in cases of hypersensitivity to the active substance(s), to any other
barbiturates or to any of the excipients
Do not use in animals with serious renal and/or cardiovascular/respiratory
disorders.
Ataxia, somnolence, listlessness and dizziness may occur rarely at the
start of treatment. In some cases, these effects may persist for the entire
duration of treatment.
A paradoxical hyperexcitability may occur rarely, particularly after first
starting therapy. As this hyperexcitability is not linked to overdosage, no
reduction of dosage is needed.
Sedation and ataxia may very rarely become significant concerns as serum
levels reach the higher end of the therapeutic range.
Polyphagia, polyuria and polydipsia have been reported rarely, but these
effects are usually transitory and disappear with continued medication.
Revised: January 2026
AN: 01910/2025Page 4 of 8
Hepatotoxicity may develop very rarely at doses over 20mg/kg/day or when
serum Phenobarbital levels are high (see special precautions for use)
Phenobarbital can have deleterious effects on stem cells from bone
marrow, immunotoxic pancytopenia and/or neutropenia and anaemia
may occur very rarely.
Superficial necrolytic dermatitis may occur after administration of
phenobarbital very rarely.
Hypoalbuminaemia was rarely reported. Phenobarbital may increase the
activity of serum alkaline phosphatase and transaminases. These may
demonstrate non-pathological changes, but could also represent
hepatotoxicity, so liver function tests are recommended (see section 4.5).
In very rare cases, change of behaviour such as aggression was reported.
If adverse effects are severe, it is recommended to decrease the daily dose.
The frequency of adverse reactions is defined using the following
convention:
- very common (more than 1 in 10 animals treated displaying
adverse reaction(s))
- common (more than 1 but less than 10 animals in 100 animals treated)
- uncommon (more than 1 but less than 10 animals in 1,000
animals treated)
- rare (more than 1 but less than 10 animals in 10,000 animals treated)
- very rare (less than 1 animal in 10,000 animals treated, including
isolated reports)
start of treatment. In some cases, these effects may persist for the entire
duration of treatment.
A paradoxical hyperexcitability may occur rarely, particularly after first
starting therapy. As this hyperexcitability is not linked to overdosage, no
reduction of dosage is needed.
Sedation and ataxia may very rarely become significant concerns as serum
levels reach the higher end of the therapeutic range.
Polyphagia, polyuria and polydipsia have been reported rarely, but these
effects are usually transitory and disappear with continued medication.
Revised: January 2026
AN: 01910/2025Page 4 of 8
Hepatotoxicity may develop very rarely at doses over 20mg/kg/day or when
serum Phenobarbital levels are high (see special precautions for use)
Phenobarbital can have deleterious effects on stem cells from bone
marrow, immunotoxic pancytopenia and/or neutropenia and anaemia
may occur very rarely.
Superficial necrolytic dermatitis may occur after administration of
phenobarbital very rarely.
Hypoalbuminaemia was rarely reported. Phenobarbital may increase the
activity of serum alkaline phosphatase and transaminases. These may
demonstrate non-pathological changes, but could also represent
hepatotoxicity, so liver function tests are recommended (see section 4.5).
In very rare cases, change of behaviour such as aggression was reported.
If adverse effects are severe, it is recommended to decrease the daily dose.
The frequency of adverse reactions is defined using the following
convention:
- very common (more than 1 in 10 animals treated displaying
adverse reaction(s))
- common (more than 1 but less than 10 animals in 100 animals treated)
- uncommon (more than 1 but less than 10 animals in 1,000
animals treated)
- rare (more than 1 but less than 10 animals in 10,000 animals treated)
- very rare (less than 1 animal in 10,000 animals treated, including
isolated reports)
The decision to start antiepileptic drug therapy with phenobarbital should be
evaluated for each individual case and depends on number, frequency, duration
and severity of seizures in dogs.
To achieve successful therapy, administration of tablets should occur at the
same time(s) each day and should be co-ordinated with feeding times in a
consistent manner.
Revised: January 2026
AN: 01910/2025Page 2 of 8
Withdrawal or transition from other types of antiepileptic therapy should be made
gradually to avoid precipitating an increase in the frequency of seizures.
Some dogs are free of epileptic seizures during the treatment, but some
dogs show only a seizure reduction, and some dogs are considered to be
non- responders.
i.
Caution is recommended in animals with:
- impaired hepatic and renal function
- hypovolemia, anaemia and
- cardiac or respiratory dysfunction
The chance of hepatotoxic side effects can be diminished or delayed using
an effective dose that is as low as possible. Monitoring of hepatic
parameters is recommended in case of a prolonged therapy.
It is recommended to assess the clinical pathology of the patient 2-3
weeks after start of treatment and afterwards every 4-6 months, e. g.
measurement of hepatic enzymes and serum bile acids. It is important to
know that the effects of hypoxia etc. do cause increased levels of hepatic
enzymes after a seizure.
Phenobarbital may increase the activity of serum alkaline phosphatase and
transaminases. These may demonstrate non-pathological changes but could
also represent hepatotoxicity. Therefore, in the case of suspected
hepatotoxicity, liver function tests are recommended.
Treating dogs with phenobarbital may lower TT4 or FT4 serum levels,
however this may not be an indication of hypothyroidism. Treatment with
thyroid hormone replacement should only be started if there are clinical signs
of the disease.
In stabilised epileptic patients, it is not recommended to switch between
phenobarbital formulations. However, if this cannot be avoided then
additional caution should be taken. This includes more frequent plasma
concentration sampling to ensure that therapeutic levels are maintained.
Monitoring for increased side effects and for hepatic dysfunction should be
conducted more regularly until stabilisation is confirmed.
A wide therapeutic range of phenobarbital concentration in the serum of 15
mg/l to 40 mg/l is often stated. Optimal seizure control is achieved in most
dogs with a serum phenobarbital concentration of between 25−30
High serum concentrations of more than 35 mg/l should be avoided due to
increased risk of hepatotoxicity. Below these ranges, in dogs with good
seizure control, no change of dose may be necessary, as the
concentration may be sufficient for that individual. As a general guide,
serum phenobarbital concentration should be the lowest to achieve a
decrease in seizure frequency of greater than 50%, or absence of seizures
Revised: January 2026
AN: 01910/2025Page 3 of 8
where possible, without intolerable side effects.
ii.
administering the veterinary medicinal product to animals
People with known hypersensitivity to phenobarbital or other barbiturates
should avoid contact with this veterinary medicinal product.
It is advisable to wear disposable gloves when handling the product, to
reduce skin contact.
Phenobarbital is a teratogen and developmental neurotoxicant and
transfers to breast milk.
The product should not be administered by pregnant women, women
intending to become pregnant or whose pregnancy status is unknown, as
well as lactating women.
Ingestion of Phenobarbital can cause neurotoxicity which may prove fatal.
Take utmost care that children do not come into any contact with the
product. Children are particularly at risk of intoxication. To prevent
accidental ingestion of tablets, the container should be closed immediately
after withdrawing the required number of tablets for one administration.
Part tablets should be placed back into the container and used at the next
administration, as even part tablets pose a health risk to small children if
ingested. The container should be stored in a safe place out of the sight
and reach of children.
In case of accidental ingestion, seek medical advice immediately and
show the package leaflet or the label to the physician. If possible, the
physician should be informed about the time and amount of ingestion, as
this information may help to ensure that appropriate treatment is given.
Wash hands thoroughly after use.
evaluated for each individual case and depends on number, frequency, duration
and severity of seizures in dogs.
To achieve successful therapy, administration of tablets should occur at the
same time(s) each day and should be co-ordinated with feeding times in a
consistent manner.
Revised: January 2026
AN: 01910/2025Page 2 of 8
Withdrawal or transition from other types of antiepileptic therapy should be made
gradually to avoid precipitating an increase in the frequency of seizures.
Some dogs are free of epileptic seizures during the treatment, but some
dogs show only a seizure reduction, and some dogs are considered to be
non- responders.
i.
Caution is recommended in animals with:
- impaired hepatic and renal function
- hypovolemia, anaemia and
- cardiac or respiratory dysfunction
The chance of hepatotoxic side effects can be diminished or delayed using
an effective dose that is as low as possible. Monitoring of hepatic
parameters is recommended in case of a prolonged therapy.
It is recommended to assess the clinical pathology of the patient 2-3
weeks after start of treatment and afterwards every 4-6 months, e. g.
measurement of hepatic enzymes and serum bile acids. It is important to
know that the effects of hypoxia etc. do cause increased levels of hepatic
enzymes after a seizure.
Phenobarbital may increase the activity of serum alkaline phosphatase and
transaminases. These may demonstrate non-pathological changes but could
also represent hepatotoxicity. Therefore, in the case of suspected
hepatotoxicity, liver function tests are recommended.
Treating dogs with phenobarbital may lower TT4 or FT4 serum levels,
however this may not be an indication of hypothyroidism. Treatment with
thyroid hormone replacement should only be started if there are clinical signs
of the disease.
In stabilised epileptic patients, it is not recommended to switch between
phenobarbital formulations. However, if this cannot be avoided then
additional caution should be taken. This includes more frequent plasma
concentration sampling to ensure that therapeutic levels are maintained.
Monitoring for increased side effects and for hepatic dysfunction should be
conducted more regularly until stabilisation is confirmed.
A wide therapeutic range of phenobarbital concentration in the serum of 15
mg/l to 40 mg/l is often stated. Optimal seizure control is achieved in most
dogs with a serum phenobarbital concentration of between 25−30
High serum concentrations of more than 35 mg/l should be avoided due to
increased risk of hepatotoxicity. Below these ranges, in dogs with good
seizure control, no change of dose may be necessary, as the
concentration may be sufficient for that individual. As a general guide,
serum phenobarbital concentration should be the lowest to achieve a
decrease in seizure frequency of greater than 50%, or absence of seizures
Revised: January 2026
AN: 01910/2025Page 3 of 8
where possible, without intolerable side effects.
ii.
administering the veterinary medicinal product to animals
People with known hypersensitivity to phenobarbital or other barbiturates
should avoid contact with this veterinary medicinal product.
It is advisable to wear disposable gloves when handling the product, to
reduce skin contact.
Phenobarbital is a teratogen and developmental neurotoxicant and
transfers to breast milk.
The product should not be administered by pregnant women, women
intending to become pregnant or whose pregnancy status is unknown, as
well as lactating women.
Ingestion of Phenobarbital can cause neurotoxicity which may prove fatal.
Take utmost care that children do not come into any contact with the
product. Children are particularly at risk of intoxication. To prevent
accidental ingestion of tablets, the container should be closed immediately
after withdrawing the required number of tablets for one administration.
Part tablets should be placed back into the container and used at the next
administration, as even part tablets pose a health risk to small children if
ingested. The container should be stored in a safe place out of the sight
and reach of children.
In case of accidental ingestion, seek medical advice immediately and
show the package leaflet or the label to the physician. If possible, the
physician should be informed about the time and amount of ingestion, as
this information may help to ensure that appropriate treatment is given.
Wash hands thoroughly after use.
Phenobarbital may reduce the activity of some drugs by increasing the rate of
metabolism through induction of drug-metabolising enzymes in liver
microsomes.
A therapeutic dose of phenobarbital for antiepileptic therapy can
significantly induce plasma protein (such as
which bind drugs. Therefore, special attention must be paid to the
pharmacokinetics and doses of drugs simultaneously administered.
The plasmatic concentration of cyclosporine, thyroid hormones and
theophylline is decreased in the case of concurrent administration of
phenobarbital. The effectiveness of these substances is diminished, too.
Concurrent use with potassium bromide increases the risk of pancreatitis.
Concurrent use with other drugs having a central depressive effect can
result in an increase of the effect of central depressive drugs.
Phenobarbital may enhance the metabolism of, and therefore decrease
the effect of, antiepileptics, chloramphenicol, corticosteroids, doxycycline,
beta blockers and metronidazole.
The reliability of oral contraceptives is lower.
Phenobarbital may decrease the blood concentration of griseofulvin by
reducing its absorption and/or inducing hepatic microsomal enzymes.
The following drugs can decrease the convulsive threshold: quinolones,
high doses of
and propofol for example). Medications which may alter the seizure
threshold should only be used if really necessary and when no safer
Revised: January 2026
AN: 01910/2025Page 6 of 8
alternative exists.
Use of phenobarbital tablets in conjunction with primidone is not
recommended as primidone is predominantly metabolized to phenobarbital.
metabolism through induction of drug-metabolising enzymes in liver
microsomes.
A therapeutic dose of phenobarbital for antiepileptic therapy can
significantly induce plasma protein (such as
which bind drugs. Therefore, special attention must be paid to the
pharmacokinetics and doses of drugs simultaneously administered.
The plasmatic concentration of cyclosporine, thyroid hormones and
theophylline is decreased in the case of concurrent administration of
phenobarbital. The effectiveness of these substances is diminished, too.
Concurrent use with potassium bromide increases the risk of pancreatitis.
Concurrent use with other drugs having a central depressive effect can
result in an increase of the effect of central depressive drugs.
Phenobarbital may enhance the metabolism of, and therefore decrease
the effect of, antiepileptics, chloramphenicol, corticosteroids, doxycycline,
beta blockers and metronidazole.
The reliability of oral contraceptives is lower.
Phenobarbital may decrease the blood concentration of griseofulvin by
reducing its absorption and/or inducing hepatic microsomal enzymes.
The following drugs can decrease the convulsive threshold: quinolones,
high doses of
and propofol for example). Medications which may alter the seizure
threshold should only be used if really necessary and when no safer
Revised: January 2026
AN: 01910/2025Page 6 of 8
alternative exists.
Use of phenobarbital tablets in conjunction with primidone is not
recommended as primidone is predominantly metabolized to phenobarbital.
Do not store above
Protect from light.
Store in a dry place and replace the closure promptly.
Protect from light.
Store in a dry place and replace the closure promptly.
Revised: January 2026
AN: 01910/2025Page 7 of 8N/A.
5.
AN: 01910/2025Page 7 of 8N/A.
5.
This information is sourced from the official Summary of Product Characteristics (SPC) published by the Veterinary Medicines Directorate (VMD). It is provided for informational purposes only and does not replace professional veterinary advice. Always consult your vet before administering any medication.
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Related Conditions
Same active ingredient
Other Products Containing Phenobarbital
These products share the same active ingredient and may be suitable alternatives. Always consult your vet.
Epiphen 30 mg Tablets
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tablet
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Epiphen 30 mg Tablets
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tablet
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Epiphen 60 mg Tablets
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tablet
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Epiphen Solution 4% w/v, Oral Drops for Dogs
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drops
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Epiphen Solution 4% w/v, Oral Drops for Dogs
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drops
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Epityl 60 mg Flavoured Tablets for Dogs
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tablet
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