Phenoleptil

10 x 10 pc

Tablet

Active substance

Phenobarbital : 100 mg

ATC code

QN03AA02 Phenobarbital

QN03AA Barbiturates and derivatives

QN03A Antiepileptics

QN03 Antiepileptics

QN Nervous system

Species

Dogs.

Indications

Prevention of seizures due to generalised epilepsy in dogs.

Dose to be administered and administration route

Oral use.

Amounts to be administered:

The recommended initial dosage is 2.5 mg phenobarbital per kg body weight twice daily. The crossed score line on one side of the tablet allows division into two (each part of 50 mg phenobarbital) or four (each part of 25 mg phenobarbital) equal parts.

Tablets must be given at the same time each day to achieve successful therapy. For accuracy of dosing, dogs under 10 kg should commence therapy with Phenoleptil 12.5mg or 25 mg Tablet.

The required dosage will differ to some extent between individuals and with the nature and severity of the disorder.

Eventual adjustments of this dosage should be made on the basis of clinical efficacy, blood levels and the occurrence of undesirable side effects. Also see the “Special precautions for safe use in the target species” section.

The serum phenobarbital concentrations should be measured after steady state has been achieved. 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. The ideal therapeutic range for serum phenobarbital concentration is between 15 and 40 µg/ml. If serum phenobarbital concentration is less than 15 µg/ml or the seizures are not controlled the dose may be increased by 20% at a time, with associated monitoring of serum phenobarbital levels up to a maximum serum concentration 45 µg/ml. The ultimate doses may vary considerably (ranging from 1 mg to 15 mg per kg body weight twice daily) because of the differences in phenobarbital excretion and differences in sensitivity among patients.

If the seizures are not being satisfactorily controlled and if the maximum level concentration is about 40 µg/ml, then the diagnosis should be reconsidered and/or a second antiepileptic veterinary medicinal product (such as bromides) should be added to the treatment protocol.

In stabilised epileptic patients, it is not recommended to switch this tablet formulation for another phenobarbital formulation. However, if this cannot be avoided then additional caution should be taken. It is recommended to try to achieve as similar dosages as possible compared with the previous formulation used, taking into consideration current plasma concentration measurements. Monitoring for increased side effects and for hepatic dysfunction should be conducted more regularly until stabilisation is confirmed. Stabilisation protocols as for initiating treatments should be followed. Withdrawal of therapy with Phenobarbital formulations should be made gradually to avoid precipitating an increase in the frequency of seizures.

Adverse reactions

Dogs:

Rare

(1 to 10 animals / 10,000 animals treated):

Ataxia ^a,d, Dizziness ^a Lethargy ^a

Very rare

(1 animal / 10,000 animals treated, including isolated reports):

Sleepiness – Neurologival disorder ^a, Sedation ^d

Hyperexcitation ^b

Polyuria ^c

Polydipsia ^c, Polyphagia ^c

Hepatic toxicosis ^e

Pancytopenia ^{f, g}, Neutropenia ^g, Low thyroxine ^h

^a During start of the therapy. These effects are usually transitory and disappear in most, but not all, patients with continued medication.

^b Paradoxical, particularly after first starting therapy. As this hyperexcitability is not linked to overdosage, no reduction of dosage is needed.

^c At average or higher therapeutic active serum concentrations; these effects can be diminished by limiting intake of both food and water.

^d Often become significant concerns as serum levels reach the higher ends of the therapeutic range.

^e Associated with high plasma concentrations.

^fImmunotoxic.

^g Consequences of deleterious effects of phenobarbital on stem cells from bone marrow. These reactions disappear after the treatment’s withdrawal.

^h 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.

If adverse effects are severe, a decrease in the administered phenobarbital dose is recommended.

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.