SUMMARY OF PRODUCT CHARACTERISTICS

1 NAME OF THE MEDICINAL PRODUCT

Phenobarbital 30mg Tablets

2 QUALITATIVE AND QUANTITATIVE COMPOSITION

Each tablet contains 30mg phenobarbital Ph. Eur.

Excipient: Lactose monohydrate 18.8mg For full list of excipients, see section 6.1

3 PHARMACEUTICAL FORM

Tablets for oral use

Appearance: White, circular, biconvex tablets

4    CLINICAL PARTICULARS

4.1    Therapeutic indications

Phenobarbital tablets are indicated for the management of all forms of epilepsy except absence seizures.

4.2 Posology and method of administration

Adults and the elderly: 60 - 180mg daily at night.

Phenobarbitol clearance diminishes in the elderly. Therefore the dose of Phenobarbitol is usually lower in elderly patients.

Children: 5 - 8mg per kg bodyweight daily.

The dose of Phenobarbitol should be adjusted to meet the needs of the individual patients. This usually requires plasma concentration of 15 to 40 micrograms/ml (65 to 170 micromoles/litre).

Administration: Oral; the tablets should be swallowed with water.

4.3 Contraindications

1.    Known hypersensitivity to barbiturates.

2.    Hypersensitivity to any of the ingredients in this medicine.

3.    Acute intermittent porphyria.

4.    Severe respiratory depression.

5.    Severe impairment of renal and hepatic function.

4.4 Special warnings and precautions for use

Suicidal ideation and behaviour have been reported in patients treated with anti-epileptic agents in several indications. A meta-analysis of randomised placebo controlled trials of anti-epileptic drugs has also shown a small increased risk of suicidal ideation and behaviour. The mechanism of this risk is not known and the available data do not exclude the possibility of an increased risk for Phenobarbital.

Therefore patients should be monitored for signs of suicidal ideation and behaviours and appropriate treatment should be considered. Patients (and caregivers of patients) should be advised to seek medical advice should signs of suicidal ideation or behaviour emerge.

Steven-Johnson syndrome and toxic epidermal necrolysis Life-threatening cutaneous reactions Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) have been reported with the use of phenobarbital. Patients should be advised of the signs and symptoms and monitored closely for skin reactions. The highest risk for occurrence of SJS or TEN is within the first weeks of treatment.

If symptoms or signs of SJS or TEN (e.g. progressive skin rash often with blisters or mucosal lesions) are present, Phenobarbital treatment should be discontinued. The best results in managing SJS and TEN come from early diagnosis and immediate discontinuation of any suspect drug. Early withdrawal is associated with a better prognosis.

If the patient has developed SJS or TEN with the use of phenobarbital, phenobarbital must not be re-started in this patient at any time.

Care should be used in the following situations:

o Patients with the rare hereditary problems of galactose intolerance, the lapp lactase deficiency or glucose - galactose malabsorption should not take this medicine

o Respiratory depression (avoid if severe) o Young, debilitated or senile patients o Renal impairment o Existing liver disease

o Sudden withdrawal should be avoided as severe withdrawal syndrome (rebound insomnia, anxiety, tremor, dizziness, nausea, fits and delirium) may be precipitated

o Acute chronic pain - paradoxical excitement may be induced or important symptoms masked.

o Prolonged use may result in dependence of the alcohol-barbiturate type. Care should be taken in treating patients with a history of drug abuse or alcoholism.

This product contains lactose. Patients with rare hereditary problems of galactose intolerance, the Lapp lactase deficiency or glucose-galactose malabsorption should not take this medicine.

4.5 Interaction with other medicinal products and other forms of interaction

o Anxiolytics and Hypnotics -clonazepam.

o Aprepitant - phenobarbital possibly reduces plasma concentration of aprepitant.

o Beta-blockers - metoprolol, timolol and possibly propranolol.

o Calcium channel blockers -phenobarbital causes reduced levels of felodipine, isradipine, diltiazem, verapamil, nimodipine and nifedipine

and an increase in dosage may be required.

o Cardiac Glycosides - blood levels of digitoxin can be halved by concurrent use.

o Ciclosporin or tacrolimus.

o Corticosteroids

o Cytotoxics - phenobarbital possibly reduces the plasma levels of etoposide or irinotecan.

o Diuretics - concomitant use with eplerenone should be avoided.

o Haloperidol- serum levels are approximately halved by concurrent used with phenobarbital.

o Hormone Antagonists - gestrinone and possibly toremifene.

o Methadone - levels can be reduced by concurrent use of phenobarbital and withdrawal symptoms have been reported in patients maintained on methadone when phenobarbital has been added. Increases in the methadone dosage may be necessary.

o Montelukast.

o Oestrogens - reduced contraceptive effect.

o Progestogens - reduced contraceptive effect.

o Sodium oxybate - enhanced effects, avoid concomitant use.

o Theophylline - may require an increase in theophylline dose.

o Thyroid hormones-may increase requirements for thyroid hormones in hypothyroidism.

o Tibolone

o Tropisetron

o Vitamins - barbiturates possibly increase requirements for vitamin D.

Phenobarbital may interfere with some laboratory tests including metyrapone test, phenlolamine tests and serum bilirubin estimation.

4.6 Fertility, Pregnancy and lactation

Phenobarbital therapy in epileptic pregnant women presents a risk to the fetus in terms of major and minor congenital defects such as congenital craniofacial, digital abnormalities and, less commonly, cleft lip and palate. The risk of

teratogenic effects developing appears to be greater if more than one antiepileptic drug is administered. The risk to the mother however is greater if phenobarbital is withheld and seizure control is lost. The risk: benefit balance, in this case, favours continued use of the drug during pregnancy at the lowest possible level to control seizures.

Patients taking phenobarbital should be adequately supplemented with folic acid before conception and during pregnancy (see section 4.5). Folic acid supplementation during pregnancy can help reduce the risk of neural defects to the infant.

Phenobarbital readily crosses the placenta following oral administration and is distributed throughout fetal tissue, the highest concentrations being found in the placenta, fetal liver and brain. Adverse effects on neurobehavioral development have also been reported.

Haemorrhage at birth and addiction are also a risk. Prophylactic treatment with vitamin K1 for the mother before delivery (as well as the neonate) is recommended, the neonate should be monitored for signs of bleeding.

Phenobarbital is excreted into breast milk and there is a small risk of neonatal sedation. Breast-feeding is therefore not advisable.

4.7 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.

4.8 Undesirable effects

Blood and lymphatic system disorders

Megaloblastic anaemia (due to folate deficiency), agranulocytosis, thrombocytopenia.

Psychiatric disorders

Paradoxical drug reaction (unusual excitement), hallucinations, restlessness, confusion in the elderly, mental depression, abnormal behaviour in children.

Nervous systems disorders

Hyperactivity, ataxia, nystagmus, memory and cognitive impairment, drowsiness, lethargy.

Vascular disorders Hypotension

Respiratory, thoracic and mediastinal disorders Respiratory depression

Hepatobiliary disorders Hepatitis, cholestasis.

Skin and subcutaneous tissue disorders

Allergic skin reactions (maculopapular morbilliform or scarlatiniform rashes), other skin reactions such as exfoliative dermatitis, erythema multiforme.

Severe cutaneous adverse reactions (SCAR): Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) have been reported (see section 4.4).

Frequency: very rare.

Musculoskeletal and connective tissue disorders Osteomalcia, rickets

General disorders and administration site conditions Hntiepileptic hypersensitivity syndrome (features include fever, rash, lymphadenopathy, lymphocytosis, eosinophilia, haematological abnormalities, hepatic and other organ involvement including renal and pulmonary systems which may become life threatening).

There have been reports of decreased bone mineral density, osteopenia, osteoporosis and fractures in patients on long-term therapy with phenobarbital.

The mechanism by which phenobarbital effects bone metabolism has not been identified.

Reporting of suspected adverse reactions

Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via the yellow card scheme at www.mhra.gov.uk/yellowcard.

4.9 Overdose

Toxicity varies between patients; tolerance will develop with chronic use. Features of poisoning are to be expected after ingestion of 1g in adults.

Features

Drowsiness, dysarthria, ataxia, nystagmus and disinhibition. There may also be coma, cardiovascular collapse, cardiac arrest, hypotension, hypotonia, hyporeflexia, hypothermia, hypotension and respiratory depression.

Barbiturates decrease gut motility, which may lead to slow onset and worsening of symptoms or cyclical improvement and worsening of symptoms.

Management

Consider activated charcoal (50g for an adult, 10-15g for a child under 5 years) if more than 10mg/kg body weight of phenobarbital has been ingested within 1 hour, provided the airway can be protected. Repeat dose activated charcoal is the best method of enhancing elimination of phenobarbital in symptomatic patients. In severe hypotension dopamine or dobutamine can be used. Treat rhabdomyolysis with urinary alkalinistion. Haemodialysis or haemofiltration may be required for cases of acute renal or severe hyperkalaemia.

Charcoal haemoperfusion is the treatment of choice for the majority of patients with severe barbiturate poisoning who fail to improve, or who deteriorate despite good supportive care.

5 PHARMACOLOGICAL PROPERTIES

5.1 Pharmacodynamic properties

Pharmacodynamic group: antiepileptics, barbiturates and derivatives ATC Code: N03 AA02

Phenobarbital has a widespread depressant action on cerebral function. It has sedative effects and has some protective action against all varieties of human partial and generalised epilepsy, with the exception of absence seizures. Phenobarbital is also effective in preventing seizures in the corresponding experimental animal models of epilepsy. In different studies phenobarbital appears to have had inconsistent effects in suppressing experimental epileptic foci, and epileptic after-discharges, but it inhibits synaptic transmission, at least in the spinal cord. The drug's probable biochemical mechanism of action is through prolonging the opening time of Cl^- ion channels in postsynaptic neuronal membranes. This effect causes membrane hyperpolarisation and thus impairs nerve impulse propagation. Phenobarbital also decreases intraneuronal Na⁺ concentrations, and inhibits Ca²⁺ influx into depolarised synaptosomes. It raises brain serotonin levels, and inhibits noradrenaline (norepinephrine) reuptake into synaptosomes. These additional biochemical actions may contribute towards the anticonvulsant effects of the drug.

5.2 Pharmacokinetic properties

Absorption - phenobarbital is readily absorbed from the gastrointestinal tract, although it is relatively lipid - insoluble; peak concentrations are reached in about 2 hours after oral administration.

Distribution - phenobarbital is about 45 to 60% bound to plasma proteins. Phenobarbital crosses the placental barrier and is distributed into breast milk.

Metabolism - the plasma half life is about 75 to 120 hours in adults but is greatly prolonged in neonates, and shorter (about 21 to 75 hours) in children. There is considerable interindividual variation in phenobarbital kinetics. Phenobarbital in only partly metabolised in the liver.

Elimination - about 25% of a dose is excreted in the urine unchanged at normal urinary pH.

5.3 Preclinical safety data

Preclinical information has not been included because of safety profile of Phenobarbital has been established after many years of clinical use. Please refer to section 4.

6 PHARMACEUTICAL PARTICULARS

6.1    List of excipients

Maize starch Lactose monohydrate Sodium lauril sulphate Sodium starch glycolate Magnesium stearate Stearic acid

6.2    Incompatibilities

Not applicable

6.3 Shelf life

3 years

6.4 Special precautions for storage

Do not store above 25°C Keep the container tightly closed Store in the original container

6.5 Nature and contents of container

Polypropylene tubes with low-density polyethylene caps Pack sizes: 28 and 1,000 tablets Not all pack sizes may be marketed