Indications
Phenobarbitone Sodium (phenobarbital sodium) is the water-soluble form of phenobarbitone, an older anti-seizure medicine. It is used to treat many types of epilepsy (generalised tonic-clonic and focal seizures), to control prolonged or repeated seizures (status epilepticus) when other medicines have not worked, and to treat seizures in newborn babies. It is sometimes used for other conditions such as withdrawal from sedatives, under specialist care.
How It Works
Phenobarbitone enhances the action of GABA, the brain’s main calming chemical messenger, and reduces excitatory signals. This raises the threshold for seizures and stops abnormal electrical activity from spreading in the brain. It also causes sedation at higher doses.
Dosage and Administration
The dose depends on age, body weight and the type of seizures, and is adjusted gradually, so use it exactly as prescribed. Injections are given into a vein or muscle by a doctor or nurse, usually in hospital and with monitoring of breathing. Tablets or elixir are usually taken once a day, often at bedtime. Never stop it suddenly, as this can cause severe withdrawal seizures; the doctor will reduce the dose slowly if it needs to be stopped.
Interactions
- Phenobarbitone speeds up the breakdown of many medicines and makes them less effective, including Warfarin, hormonal contraceptives, corticosteroids, Doxycycline, some HIV medicines, Ciclosporin, Lamotrigine and Carbamazepine.
- Alcohol, opioids, benzodiazepines, sedating antihistamines and other sleep medicines: dangerous drowsiness and slowed breathing.
- Sodium Valproate: raises phenobarbitone levels, increasing sleepiness.
- Phenytoin: levels of either medicine may change.
- Folic Acid: may lower phenobarbitone levels; Phenobarbitone may lower folate.
Contraindications
Do not use if you are allergic to barbiturates, have acute porphyria (a rare inherited blood disorder), severe breathing problems, or severe liver or kidney failure, unless the specialist decides otherwise.
Side Effects
- Drowsiness, tiredness, slowed thinking and poor concentration.
- Unsteadiness and dizziness, especially in older people.
- Restlessness, excitability or behaviour changes in children and the elderly.
- Depression or low mood.
- With long-term use: low folate (anaemia), weak bones (low vitamin D), joint stiffness.
Get urgent medical help for slow or shallow breathing, extreme sleepiness or difficulty waking, a skin rash with blisters, peeling or mouth sores, fever with swollen glands, yellow skin or eyes, unusual bruising or bleeding, or thoughts of suicide or self-harm.
Pregnancy and Lactation
Phenobarbitone can increase the risk of birth defects and may affect the baby’s development, and newborns may have withdrawal symptoms or bleeding problems. However, uncontrolled seizures are also dangerous. Do not stop it on your own: speak to your doctor before pregnancy about the safest treatment and about Folic Acid supplements. It passes into breast milk and may make the baby drowsy; breastfeed only on medical advice and watch the baby closely.
Precautions and Warnings
It can be habit-forming and is a controlled medicine. Do not drive or operate machinery until you know how it affects you, and avoid alcohol. It reduces the effect of hormonal contraceptives, so use another reliable method. Use with care in the elderly, children, people with depression, liver or kidney disease, breathing problems or a history of drug or alcohol misuse. Regular blood tests may be needed.
Overdose
Overdose is a medical emergency and can cause deep sleep, coma, very slow breathing, low blood pressure, low body temperature and death. Call emergency services at once.
Therapeutic Class
Barbiturate anticonvulsant (anti-epileptic).
Storage
Store below 30°C in a dry place, away from light, in a secure place out of the reach of children. Injections: store as directed on the pack.
Prepared by the Oshud Alo team from standard drug references. For information only; always follow your doctor's advice.