Phenoba

Indications

Phenobarbitone (phenobarbital) is used to control epilepsy, including generalised tonic-clonic seizures (fits with stiffening and jerking) and focal seizures. The injection is used in hospital to stop prolonged or repeated fits (status epilepticus) and to treat seizures in newborn babies.

How It Works

It is a barbiturate. It strengthens the effect of GABA, the brain's natural calming chemical, which makes nerve cells less likely to fire in the bursts that cause seizures.

Dosage and Administration

• Adults with epilepsy: usually 60 to 180 mg once a day, often at bedtime, as prescribed. The doctor adjusts the dose to control fits with the fewest side effects.
• Children: dose is worked out by body weight; only as prescribed.
• Injection: given by a doctor or nurse in hospital.
• Take it at the same time every day. Do not stop suddenly, as this can bring on severe fits; the doctor will reduce the dose slowly if it needs to be stopped.

Interactions

• Alcohol, sleeping tablets, Diazepam and other benzodiazepines, opioid painkillers and sedating antihistamines add to drowsiness and can slow breathing dangerously.
• It speeds up the breakdown of many medicines and makes them weaker, including hormonal contraceptives, Warfarin, steroids, Doxycycline, some heart medicines, some HIV medicines and other epilepsy medicines such as Carbamazepine and Lamotrigine.
• Sodium Valproate raises phenobarbitone levels and can cause heavy drowsiness.

Contraindications

• Allergy to phenobarbitone or other barbiturates.
• Acute porphyria (a rare inherited blood disorder).
• Severe breathing problems or severe liver or kidney disease.

Side Effects

Common: drowsiness, tiredness, dizziness, unsteadiness, slowed thinking and poor memory or concentration. Children and older people may become restless, irritable or confused. Long-term use can lower folic acid and vitamin D levels and weaken bones.

Get urgent medical help if you have a skin rash with fever, blisters or mouth sores, yellow skin or eyes, unusual bruising or bleeding, very slow or shallow breathing, extreme sleepiness, or low mood or thoughts of harming yourself.

Pregnancy and Lactation

It can increase the risk of birth defects and can cause bleeding or withdrawal symptoms in the newborn. Do not stop it on your own if you become pregnant, because uncontrolled fits are also dangerous. Plan pregnancy with your doctor, who may advise folic acid. It passes into breast milk and can make the baby sleepy; breastfeed only with the doctor's advice and watch the baby for drowsiness or poor feeding.

Precautions and Warnings

It can cause dependence with long use, and stopping suddenly causes withdrawal and fits. It weakens hormonal contraception, so use another method. Do not drive or operate machinery if you feel drowsy. Use with care in older people and in people with depression, liver or kidney disease, or lung disease. Regular check-ups and sometimes blood level tests are needed. Keep it safely, as it is a controlled medicine.

Overdose

An overdose is dangerous and can cause deep sleep, slow breathing, low blood pressure, coma and death. Get emergency medical help at once.

Therapeutic Class

Antiepileptic (anticonvulsant), barbiturate.

Storage

Store below 30°C in a dry place, away from light and out of the reach of children.