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PHENOBARBITAL ELIXIR B.P.
NAME OF THE MEDICINAL PRODUCT
Phenobarbital Elixir B.P.
QUALITATIVE AND QUANTITATIVE COMPOSITION
Phenobarbital 15 mg/5 ml dose
For excipients, see 6.1.
For all forms of epilepsy except absence seizures.
To be used in accordance with the directions of an appropriate medical
Posology and method of administration
For oral administration.
The dose should be adjusted to the needs of the individual patient to achieve
adequate control of seizures; this usually requires plasma concentrations of 10
to 40 mcg/ml (40 - 160 micromol/litre). Usual doses are:Adults, the elderly and children over 12 years
20 - 60 ml (60 - 180 mg) daily, taken at night.
Children under 12 years
5 - 8 mg/kg daily.
Known hypersensitivity to barbiturates or any of the other ingredients, acute
intermittent porphyria, severe respiratory depression, severe impairment of
renal and hepatic function.
Special warnings and precautions for use
Phenobarbital should be used with caution in the young, debilitated or senile
patients and in those with renal impairment, existing liver disease or
respiratory depression (should be avoided if severe).
Prolonged use may result in dependence of the alcohol-barbiturate type and
particular care should be taken in treating patients with a history of drug abuse
Avoid sudden withdrawal to prevent rebound seizures.
Interaction with other medicinal products and other forms of interaction
Phenobarbital may induce liver microsomal enzymes and the rate of
metabolism of certain drugs can be increased and serum concentrations of the
following drugs may be reduced; coumarin anticoagulants, phenylbutazone,
systemic steroids including gestrinone, tibolone and oral contraceptives (which
may lead to contraceptive failure), griseofulvin, rifampicin, phenothiazines,
tricyclic antidepressants, mianserin, haloperidol, chloramphenicol,
doxycycline, metronidazole, telithromycin, voriconazole, HIV protease
inhibitors, cyclosporin, calcium channel antagonists (especially felodipine,
verapamil, nimodipine and nifedipine may require an increase in dosage),
theophylline, digitoxin, disopyramide, toremifene, montelukast and
Concomitant administration of phenobarbitone with other antiepileptics may
enhance toxicity without a corresponding increase in the antiepileptic effect.
Interactions are usually caused by hepatic enzyme inhibition or hepatic
enzyme induction. Oxcarbazepine, phenytoin and valproate often raise the
plasma concentration of phenobarbitone. Conversely, vigabatrin sometimes
lowers the plasma concentration of phenobarbitone. The plasma levels of
phenytoin, carbamazepine, lamotrigine, clonazepam, ethosuximide, tiagabine
and valproate are likely to be reduced when used concomitantly with
The phenobarbitone plasma concentration is possibly reduced by folic acid.
The effect of phenobarbital can be reduced by concomitant use of the herbal
remedy St. John’s wort (Hypericum perforatum).
Antidepressants and antipsychotics can produce antagonism of the
anticonvulsant effect by lowering the convulsive threshold.
Phenobarbital has been shown to reduce the response to thyroxine. Prescribers
should be alert for changes in thyroid status if barbiturates are added or
withdrawn from patients being treated for hypothyroidism.
Concurrent administration with alcohol may lead to an additive CNS
In addition, sedative effects may occur with phenytoin and sodium valproate.
Pregnancy and lactation
The use of phenobarbital in pregnancy, especially the first and third trimesters,
should be avoided unless it is considered to be essential. Phenobarbital can
cross the placental barrier and there is an increased risk of teratogenicity.
Neonatal bleeding may occur and prophylactic treatment with vitamin K1 for
mother before delivery (as well as for the neonate) is recommended.
Patients taking phenobarbital should be adequately supplemented with folic
acid before conception and during pregnancy.
Phenobarbital is excreted into breast milk and there is a small risk of neonatal
sedation. Breast feeding is, therefore, not advisable.
Effects on ability to drive and use machines
Phenobarbital may impair the mental and/or physical abilities required for the
performance of potentially hazardous tasks such as driving or operating
machinery. If patients are affected they should not drive or operate machinery.
Memory and cognitive impairment, hyperactivity and behavioural disturbance.
Drowsiness, lethargy, mental depression. Ataxia, nystagmus and respiratory
depression. Megaloblastic anaemia (due to folate deficiency). Hepatitis,
cholestasis and osteomalacia have been associated with barbiturate
administration. Allergic skin reactions-maculopapular, morbilliform or
scarlatiniform rashes. Severe reactions such as exfoliative dermatitis,
erythema multiforme and toxic epidermal necrolysis are extremely rare.
Drowsiness, coma, respiratory depression, hypotension and hypothermia. The
duration and depth of cerebral depression varies with the dose and tolerance of
the patient. Supportive measures alone may be sufficient if symptoms are
mild. If within 4 hours of ingestion, gastric aspiration or lavage may be of
benefit in adults. The prime objective of treatment is to maintain vital
functions while the majority of the drug is metabolised by hepatic enzymes.
Given normal renal function, forced alkaline diuresis (maintaining the urinary
pH at approximately 8 by intravenous infusion) may enhance the excretion of
the drug from the kidneys. Charcoal haemoperfusion is the treatment of
choice for the majority of patients with very severe barbiturate poisoning who
fail to improve, or who deteriorate despite good supportive care.
ATC Code: NO3A A Barbiturates and derivatives.
Phenobarbital is a long-acting barbiturate with anticonvulsant properties. It
has a protective action against all varieties of human partial and generalised
epilepsy, with the exception of absence seizures. It limits the spread of
seizure activity and elevates seizure threshold.
Phenobarbital is completely (>90%), but slowly, absorbed after oral
administration, with peak levels generally occurring in 6 - 18 hours. It is 40 - 60%
bound to plasma proteins. Phenobarbital diffuses across the placenta, and is excreted
in breast milk.
Up to about 25% of a dose is eliminated by pH-dependent renal excretion of
the unchanged drug. The remainder is inactivated by hepatic microsomal enzymes.
One major metabolite, the parahydroxyphenol derivative, is
inactive and is
excreted in the urine, partly as the glucuronide conjugate. Another major metabolite
is the n-glucoside derivative.
The plasma half-life of phenobarbital is about 100 hours in adults. It is
somewhat longer in neonates and shorter (about 75 hours) and more variable
in children. The half-life is increased in the elderly, in overdosage and in renal and
Preclinical safety data
No relevant data.
List of excipients
Terpeneless Orange Oil
Terpeneless Lemon Oil
Coriander Oil Flavouring
Sunset Yellow Eurocert 311831
Ethanol (96% v/v)
No major incompatibilities have been reported.
Special precautions for storage
Store in the original container.
Nature and contents of container
2000 ml white polythene bottle with a white plastic screw cap with an
aluminium faced EPE liner.
500 ml white polythene bottle with a white wadless screw cap.
100 ml amber glass bottle with a plastic Jay cap closure.
Not all pack sizes may be marketed.
Special precautions for disposal
MARKETING AUTHORISATION HOLDER
Wise Pharmaceuticals Limited,
Hani Wells Business Park,
MARKETING AUTHORISATION NUMBER(S)
DATE OF FIRST AUTHORISATION/RENEWAL OF THE
DATE OF REVISION OF THE TEXT
Source: Medicines and Healthcare Products Regulatory Agency
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