POM-V
Prescription Required
Companion Animal
Phenocoat 50 mg Film-coated Tablets for Dogs
Active ingredient: Phenobarbital
Form
Tablet
Species
Dogs
Manufacturer
Alfasan Nederland B.V.
VMD MA No.
36408/5035
What it's used for
Phenobarbital is an antiepileptic agent for use in the control of epilepsy in the dog.
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Paying less for Phenobarbital
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Prescription required
Your vet must provide a written prescription on request. You can then purchase from any licensed online retailer.
Clinical information
Phenocoat 50 mg Film-coated Tablets for Dogs — SPC Details
Source: VMD Summary of Product Characteristics (SPC). Last updated 27 Mar 2026.
Phenobarbital is an antiepileptic agent for use in the control of epilepsy in the dog.
The recommended starting dose is 2.5 mg phenobarbital per kg body weight,
administered twice daily q12h (every 12 hours).
To ensure a correct starting dosage, body weight should be determined as
accurately as possible.
Tablets must be given at the same time each day to achieve successful therapy.
Steady state serum concentrations are not reached until 1-2 weeks after treatment is
initiated, and therefore initial efficacy of the medication may vary and doses should
not be increased during this time.
Any adjustments to the starting dose are best made on the basis of clinical efficacy,
blood concentrations of phenobarbital and the occurrence of adverse events.
Determining serum phenobarbital concentration is essential for providing appropriate
therapy, the time to reach steady state (1-2 weeks) and increased metabolism due to
auto-induction (6 weeks) should be kept in mind when determining a serum
concentration monitoring plan.
The phenobarbital concentrations considered therapeutically effective vary from 15
to 40 μg/ml, but in most dogs, serum phenobarbital concentration between 25−30
µg/ml is required for optimal seizure control.
Due to differences in the excretion of phenobarbital and differences in sensitivity, the
effective doses may vary considerably between patients (from 1 mg to 15 mg/kg
body weight twice a day).
In case of insufficient therapeutic efficacy, the dosage can be increased in steps of
20% at a time, with associated monitoring of serum phenobarbital concentrations.
Due to auto-induction of hepatic microsomal enzymes, in some dogs phenobarbital
half-life can become shorter than 20h after chronic treatment. In those cases, to
minimise therapeutically relevant fluctuation of serum concentrations, an 8-h dosing
interval could be considered.
If the seizures are not being satisfactorily prevented and if the maximum level
concentration is about 40 μg/ml, then the diagnosis should be reconsidered and/or a
second antiepileptic product should be added to the treatment protocol.
Plasma concentrations should always be interpreted in conjunction with the
observed response to therapy and a full clinical assessment including monitoring for
evidence of toxic effects in each animal.
Please note that this dosing table is intended as a guide for dispensing the veterinary
medicinal product at the recommended starting dose for each administration: 2.5
mg/kg. It states the number and type of tablets required to administer 2.5 mg
phenobarbital per kg bodyweight per administration.
Body
weight
Phenocoat
5 mg
Phenocoat
12.5 mg
Phenocoat
25 mg
Phenocoat
50 mg
2 kg4 kg5 kg7 kg AND10 kg20 kg30 kg AND40 kg50 kg AND60 kg
A suitable combination of tablet sizes should be used in order to administer the
optimal dosage for each dog.
administered twice daily q12h (every 12 hours).
To ensure a correct starting dosage, body weight should be determined as
accurately as possible.
Tablets must be given at the same time each day to achieve successful therapy.
Steady state serum concentrations are not reached until 1-2 weeks after treatment is
initiated, and therefore initial efficacy of the medication may vary and doses should
not be increased during this time.
Any adjustments to the starting dose are best made on the basis of clinical efficacy,
blood concentrations of phenobarbital and the occurrence of adverse events.
Determining serum phenobarbital concentration is essential for providing appropriate
therapy, the time to reach steady state (1-2 weeks) and increased metabolism due to
auto-induction (6 weeks) should be kept in mind when determining a serum
concentration monitoring plan.
The phenobarbital concentrations considered therapeutically effective vary from 15
to 40 μg/ml, but in most dogs, serum phenobarbital concentration between 25−30
µg/ml is required for optimal seizure control.
Due to differences in the excretion of phenobarbital and differences in sensitivity, the
effective doses may vary considerably between patients (from 1 mg to 15 mg/kg
body weight twice a day).
In case of insufficient therapeutic efficacy, the dosage can be increased in steps of
20% at a time, with associated monitoring of serum phenobarbital concentrations.
Due to auto-induction of hepatic microsomal enzymes, in some dogs phenobarbital
half-life can become shorter than 20h after chronic treatment. In those cases, to
minimise therapeutically relevant fluctuation of serum concentrations, an 8-h dosing
interval could be considered.
If the seizures are not being satisfactorily prevented and if the maximum level
concentration is about 40 μg/ml, then the diagnosis should be reconsidered and/or a
second antiepileptic product should be added to the treatment protocol.
Plasma concentrations should always be interpreted in conjunction with the
observed response to therapy and a full clinical assessment including monitoring for
evidence of toxic effects in each animal.
Please note that this dosing table is intended as a guide for dispensing the veterinary
medicinal product at the recommended starting dose for each administration: 2.5
mg/kg. It states the number and type of tablets required to administer 2.5 mg
phenobarbital per kg bodyweight per administration.
Body
weight
Phenocoat
5 mg
Phenocoat
12.5 mg
Phenocoat
25 mg
Phenocoat
50 mg
2 kg4 kg5 kg7 kg AND10 kg20 kg30 kg AND40 kg50 kg AND60 kg
A suitable combination of tablet sizes should be used in order to administer the
optimal dosage for each dog.
Do not use in cases of hypersensitivity to the active substance or other barbiturates.
Do not use in animals with severe liver disease, serious renal or cardiovascular
disorders.
Do not use in animals with severe liver disease, serious renal or cardiovascular
disorders.
Dogs:
Very common
(>1 animal / 10 animals
treated):
polyphagia
, polydipsia
, lethargy
,
polyuria,
sedation
, ataxia
,
elevated liver enzymes
.
Common
(1 to 10 animals / 100 animals
treated):
hyperexcitation
.Uncommon
(1 to 10 animals / 1,000
animals treated):
blood dyscrasia (such as anaemia, and/or
thrombocytopenia, and/or neutropenia)
,
hypoalbuminaemia
, elevated serum lipids,
dyskinesia
,
anxiety
,
hepatic toxicosis
pancreatitis.
undetermined frequency
(cannot be estimated from
available data)
diarrhoea, emesis.
dermatitis
.
low thyroxine (T4)
1
These effects are usually transitory (10-21 days) and disappear with continued
medication.
These may be associated with non-pathological changes, but could also represent
hepatotoxicity.
Particularly observed after initiation of therapy. As this hyperexcitation is not linked
to overdosage, no reduction of dosage is needed.
Reversible with reduction of dosage or discontinuation of phenobarbital therapy.
Associated with long-term use of phenobarbital and high therapeutic doses (> 20
mg/kg/day) or high serum concentrations (≥
with discontinuation of the drug if identified early in the course of disease.
Superficial necrolytic dermatitis as part of the anticonvulsant hypersensitivity
syndrome (AHS).
Lower total T4 or free T4 serum levels may not be an indication of hypothyroidism.
Treatment with thyroid hormone replacement should only be started if there are
clinical signs of the disease.
Reporting adverse events is important. It allows continuous safety monitoring of a
veterinary medicinal product. Reports should be sent, preferably via a veterinarian,
to either the marketing authorisation holder or its local representative or the national
competent authority via the national reporting system. See the package leaflet for
respective contact details.
Very common
(>1 animal / 10 animals
treated):
polyphagia
, polydipsia
, lethargy
,
polyuria,
sedation
, ataxia
,
elevated liver enzymes
.
Common
(1 to 10 animals / 100 animals
treated):
hyperexcitation
.Uncommon
(1 to 10 animals / 1,000
animals treated):
blood dyscrasia (such as anaemia, and/or
thrombocytopenia, and/or neutropenia)
,
hypoalbuminaemia
, elevated serum lipids,
dyskinesia
,
anxiety
,
hepatic toxicosis
pancreatitis.
undetermined frequency
(cannot be estimated from
available data)
diarrhoea, emesis.
dermatitis
.
low thyroxine (T4)
1
These effects are usually transitory (10-21 days) and disappear with continued
medication.
These may be associated with non-pathological changes, but could also represent
hepatotoxicity.
Particularly observed after initiation of therapy. As this hyperexcitation is not linked
to overdosage, no reduction of dosage is needed.
Reversible with reduction of dosage or discontinuation of phenobarbital therapy.
Associated with long-term use of phenobarbital and high therapeutic doses (> 20
mg/kg/day) or high serum concentrations (≥
with discontinuation of the drug if identified early in the course of disease.
Superficial necrolytic dermatitis as part of the anticonvulsant hypersensitivity
syndrome (AHS).
Lower total T4 or free T4 serum levels may not be an indication of hypothyroidism.
Treatment with thyroid hormone replacement should only be started if there are
clinical signs of the disease.
Reporting adverse events is important. It allows continuous safety monitoring of a
veterinary medicinal product. Reports should be sent, preferably via a veterinarian,
to either the marketing authorisation holder or its local representative or the national
competent authority via the national reporting system. See the package leaflet for
respective contact details.
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
Early treatment is warranted because repetitive seizures may create additional
seizure foci.
Therapeutic phenobarbital serum concentrations should be monitored to enable the
lowest effective dose to be used. The individual variability in phenobarbital
metabolism is high. Due to auto-induction of hepatic microsomal enzymes (see
section 4.3 pharmacokinetics) increasing dose increments might be necessary over
time to maintain the same serum concentration.
Some of the dogs are free of epileptic seizures during the treatment, but some of the
dogs show only a seizure reduction, and some of the dogs are considered to be non-
responders.
Special precautions for safe use in the target species:
Caution is required in animals with impaired liver and / or renal function,
hypovolaemia, anaemia and cardiac or respiratory dysfunction.
It is recommended that the clinical pathology (haematology and clinical chemistry,
including hepatic function and thyroid function) of the patient is evaluated prior to
initiation of therapy and monitored 2-3 weeks after initiation of therapy and
subsequently every 4-6 months.
The chance of hepatotoxic side effects can be diminished or delayed using an
effective dose that is as low as possible.
In the case of suspected hepatotoxicity, liver function tests are recommended. In
case of acute hepatic failure or chronic liver cell damage phenobarbital must be
discontinued and replaced by another type of antiepileptic therapy.
Withdrawal of phenobarbital or transition to or from another type of antiepileptic
therapy should be made gradually to avoid precipitating an increase in the frequency
of seizures.
In stabilised epileptic patients, caution should be taken when switching between
phenobarbital formulations.
Special precautions to be taken by the person administering the veterinary medicinal
product to animals
Phenobarbital may cause serious effects, such as sedation, disorientation, ataxia,
nystagmus, and can be fatal after accidental ingestion by children. To avoid
accidental ingestion, take utmost care that children do not come in contact with the
film-coated tablets. The tablets should be carefully kept away from children. Keep
the tablets in the original packaging prior to use.
In case of accidental ingestion, seek medical advice immediately and show the
package leaflet or the label to the physician.
Special precautions for the protection of the environment:
Not applicable.
evaluated for each individual case and depends on number, frequency, duration and
severity of seizures in dogs
Early treatment is warranted because repetitive seizures may create additional
seizure foci.
Therapeutic phenobarbital serum concentrations should be monitored to enable the
lowest effective dose to be used. The individual variability in phenobarbital
metabolism is high. Due to auto-induction of hepatic microsomal enzymes (see
section 4.3 pharmacokinetics) increasing dose increments might be necessary over
time to maintain the same serum concentration.
Some of the dogs are free of epileptic seizures during the treatment, but some of the
dogs show only a seizure reduction, and some of the dogs are considered to be non-
responders.
Special precautions for safe use in the target species:
Caution is required in animals with impaired liver and / or renal function,
hypovolaemia, anaemia and cardiac or respiratory dysfunction.
It is recommended that the clinical pathology (haematology and clinical chemistry,
including hepatic function and thyroid function) of the patient is evaluated prior to
initiation of therapy and monitored 2-3 weeks after initiation of therapy and
subsequently every 4-6 months.
The chance of hepatotoxic side effects can be diminished or delayed using an
effective dose that is as low as possible.
In the case of suspected hepatotoxicity, liver function tests are recommended. In
case of acute hepatic failure or chronic liver cell damage phenobarbital must be
discontinued and replaced by another type of antiepileptic therapy.
Withdrawal of phenobarbital or transition to or from another type of antiepileptic
therapy should be made gradually to avoid precipitating an increase in the frequency
of seizures.
In stabilised epileptic patients, caution should be taken when switching between
phenobarbital formulations.
Special precautions to be taken by the person administering the veterinary medicinal
product to animals
Phenobarbital may cause serious effects, such as sedation, disorientation, ataxia,
nystagmus, and can be fatal after accidental ingestion by children. To avoid
accidental ingestion, take utmost care that children do not come in contact with the
film-coated tablets. The tablets should be carefully kept away from children. Keep
the tablets in the original packaging prior to use.
In case of accidental ingestion, seek medical advice immediately and show the
package leaflet or the label to the physician.
Special precautions for the protection of the environment:
Not applicable.
Phenobarbital induces both plasma proteins such as ɑ1-acid glycoprotein and
hepatic microsomal cytochrome P450 (CYP) enzymes which can lead to drug-drug
interactions. Therefore, special attention must be paid to the pharmacokinetics and
doses of drugs administered simultaneously.
The induction of plasma proteins results in an increased binding to plasma proteins
and thus a lower unbound fraction of substances in plasma. The induction of CYP
enzymes may result in a higher metabolism of substances metabolized by these
enzymes, and thus a lower concentration of substances in plasma, including
phenobarbital itself.
The therapeutic effect of benzodiazepines, such as diazepam, may be decreased in
animals which are treated chronically with phenobarbital. This is particularly
important in cases of in animals treated chronically with
phenobarbital.
The plasma concentrations and thus the therapeutic effects of other anti-epileptic
drugs, such as levetiracetam and zonisamide, may be decreased by phenobarbital
when used simultaneously.
Phenobarbital is synergistic with other GABA-ergic drugs such as bromide.
As phenobarbital is partially metabolized by CYP enzymes, substances that inhibit
CYP enzyme activity, may cause an increased plasma concentration of
phenobarbital. Several substances have been identified as CYP inhibitors in humans
and laboratory animals and/or in-vitro studies. The clinical impact of these
interactions is considered low when these substances are used at therapeutical
doses, however possible interactions cannot be excluded completely. Examples of
such substances are: ketoconazole, griseofulvin, chloramphenicol, ɑ2-agonist
as medetomidine and xylazine, atipamezole, propofol.
hepatic microsomal cytochrome P450 (CYP) enzymes which can lead to drug-drug
interactions. Therefore, special attention must be paid to the pharmacokinetics and
doses of drugs administered simultaneously.
The induction of plasma proteins results in an increased binding to plasma proteins
and thus a lower unbound fraction of substances in plasma. The induction of CYP
enzymes may result in a higher metabolism of substances metabolized by these
enzymes, and thus a lower concentration of substances in plasma, including
phenobarbital itself.
The therapeutic effect of benzodiazepines, such as diazepam, may be decreased in
animals which are treated chronically with phenobarbital. This is particularly
important in cases of in animals treated chronically with
phenobarbital.
The plasma concentrations and thus the therapeutic effects of other anti-epileptic
drugs, such as levetiracetam and zonisamide, may be decreased by phenobarbital
when used simultaneously.
Phenobarbital is synergistic with other GABA-ergic drugs such as bromide.
As phenobarbital is partially metabolized by CYP enzymes, substances that inhibit
CYP enzyme activity, may cause an increased plasma concentration of
phenobarbital. Several substances have been identified as CYP inhibitors in humans
and laboratory animals and/or in-vitro studies. The clinical impact of these
interactions is considered low when these substances are used at therapeutical
doses, however possible interactions cannot be excluded completely. Examples of
such substances are: ketoconazole, griseofulvin, chloramphenicol, ɑ2-agonist
as medetomidine and xylazine, atipamezole, propofol.
This veterinary medicinal product does not require any special storage conditions.
Not applicable.
4.
4.
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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