PHENOBARBITON

Phenobarbiton HF contains the active substance phenobarbital, which belongs to a group of medicines called barbiturates. These medicines reduce the brain activity responsible for epileptic seizures – according to the leaflet, all types of seizures except absence seizures.

The medicine is made by Hemofarm AD Vršac in strengths of 15 mg and 100 mg. Because it contains a controlled narcotic substance, it is supplied only on a prescription issued in duplicate.

What Phenobarbiton HF is used for and how to take it

Key facts about the medicine

Indications

According to the leaflet, Phenobarbiton HF is used to prevent epileptic seizures (all types except absence seizures). The medicine is prescribed and dosed by a doctor.

Dosage and method of administration

Take the tablets with water every day at the same time, exactly as your doctor has told you.

• Adults: 60–180 mg at bedtime.
• Children: 5–8 mg per kg body weight per day.
• Elderly: the doctor may prescribe a lower dose.

If you miss a dose, take it as soon as possible; if it is almost time for the next dose, continue with your usual schedule. Never take a double dose. Stopping suddenly can cause withdrawal symptoms: drowsiness, anxiety, tremor, light-headedness, nausea, convulsions and delirium.

Contraindications – when the medicine must not be used

• allergy to phenobarbital, other barbiturates or any of the excipients;
• acute intermittent porphyria;
• severe kidney or liver disease;
• severely impaired breathing (respiratory depression);
• acute poisoning with alcohol, sedatives, hypnotics, analgesics, psychostimulants or other CNS depressants.

Warnings and precautions

• a history of alcohol or drug dependence – prolonged use may lead to dependence;
• impaired liver or kidney function, respiratory disease, severely damaged heart muscle, acute or chronic pain;
• mood disorders in you or your family – a small number of people treated with antiepileptics have suicidal thoughts; seek help immediately;
• serious skin reactions (Stevens-Johnson syndrome, toxic epidermal necrolysis) and antiepileptic hypersensitivity syndrome, most often in the first weeks of treatment;
• avoid strong sunlight because the skin may become more sensitive to light;
• with long-term use, because of the effect on bones, regular check-ups and taking vitamin D and folic acid are recommended;
• special caution in children, the elderly and debilitated patients; monitoring of serum levels is recommended.

Interactions with other medicines, food and drink

Phenobarbital interacts with a large number of medicines. The leaflet lists, among others: calcium channel blockers, anticoagulants, some antibiotics (doxycycline, metronidazole, rifampicin), ciclosporin and tacrolimus, beta blockers, antifungals (voriconazole, itraconazole), antiviral medicines, oral contraceptives (possible contraceptive failure), theophylline, thyroid hormones, antidepressants, other antiepileptics, antipsychotics, corticosteroids, paracetamol, folic acid, vitamin D and St John's wort, which lowers phenobarbital levels. It can also affect the results of some laboratory tests. Alcohol must not be consumed during treatment.

Pregnancy and breast-feeding

Phenobarbital taken during pregnancy can cause serious birth defects (cleft lip and palate, heart defects and others); the risk of major malformations rises about 2–3-fold compared with the general population, and neurodevelopmental disorders have also been reported. It is used in pregnancy only if the benefit outweighs the risk, at the lowest effective dose. Women of childbearing potential should use effective contraception during treatment and for two months afterwards. Do not stop treatment without your doctor. Adequate folic acid supplementation before and during pregnancy is recommended. Do not breast-feed during treatment.

Driving and using machines

Phenobarbital strongly affects psychophysical abilities – driving and operating machinery are not permitted during treatment.

Possible side effects

Very common (more than 1 in 10 patients): memory disturbances, confusion, sedation, dizziness, vertigo, fainting, headache, movement disorder, loss of coordination, sexual dysfunction, tiredness, drowsiness, weakness and prolonged reaction time.

Common and less frequent side effects include paradoxical excitement and irritability, as well as other reactions listed in the patient leaflet. Signs of overdose are drowsiness, slurred speech, jerking movements, double vision, reduced reflexes, low body temperature and blood pressure, and difficulty breathing.

Composition, pack and manufacturer

• Active substance: phenobarbital 15 mg (Phenobarbiton HF 15 mg) or 100 mg (Phenobarbiton HF 100 mg) per tablet.
• Excipients (15 mg): lactose monohydrate; maize starch; potato starch; talc; magnesium stearate; gelatin.
• Excipients (100 mg): lactose monohydrate; maize starch; talc; magnesium stearate; gelatin.
• Pack: PVC/Al blister of 10 tablets; 3 blisters (30 tablets) per box.
• Marketing authorisation holder and manufacturer: Hemofarm AD Vršac, Beogradski put bb, Vršac, Serbia.

Storage

• Keep out of the reach and sight of children.
• Store below 25 °C in the original package to protect from light and moisture.
• Do not use after the expiry date.
• Return unused medicine to a pharmacy that collects unused medicines.

Frequently asked questions

Why are vitamin D and folic acid recommended with phenobarbital?

According to the leaflet, long-term use of phenobarbital may affect the bones, so regular check-ups and taking vitamin D and folic acid are recommended. Folic acid is especially important before and during pregnancy.

Does phenobarbital reduce the effect of birth control pills?

Yes. Phenobarbital can make hormonal contraceptives less effective. The leaflet advises effective contraception during treatment and for two months afterwards, with the method agreed with your doctor.

Can I drive while taking Phenobarbiton HF?

No. Phenobarbital strongly affects psychophysical abilities, so driving and operating machinery are not permitted during treatment.

What happens if I stop taking it suddenly?

Stopping suddenly can trigger seizures and withdrawal symptoms (anxiety, tremor, nausea, convulsions, delirium). Treatment is stopped only gradually, as instructed by your doctor.

Sources

• ALIMS – Patient leaflet for Phenobarbiton HF 15 mg and 100 mg tablets (Serbian)
• ALIMS – Summary of product characteristics for Phenobarbiton HF (Serbian)