phenobarbital sodium at a glance
Medicine class
Barbiturate antiseizure treatment
Licensed role
Epilepsy other than absence seizures
Oral suspension
Shake well and measure with the supplied oral syringe
Important caution
May cause sleepiness, dizziness and impaired coordination
What is phenobarbital sodium used for?
The selected products are licensed as anticonvulsants.
Treatment of epilepsy in adults and children, except absence seizures.
The oral suspension may be used alone or with another antiseizure treatment.
How does phenobarbital sodium work?
Phenobarbital enhances inhibitory signalling at GABA-A receptors, keeping neuronal chloride channels open longer. This makes nerve cells less likely to fire and helps prevent seizure activity, while also causing sedative effects.
phenobarbital sodium preparations and strengths
Oral suspension
Route: Oral
Strengths: 50 mg/5 mL
Injection
Route: Parenteral
Strengths: 30 mg/mL, 60 mg/mL, 200 mg/mL
How to take phenobarbital sodium
Follow the product-specific instructions and prescription. The injection is administered by a healthcare professional.
Shake the oral suspension well before every administration.
Use the supplied oral syringe rather than a household spoon.
For a child, keep them upright and deliver the suspension slowly into the inside of the cheek.
The oral suspension may be given through compatible nasogastric or gastrostomy tubes, with flushing before and after administration.
Rinse the oral syringe with water and allow it to air dry.
phenobarbital sodium side effects
Common or expected effects
- Drowsiness or sedation
- Memory or concentration problems
- Behavioural change, agitation or aggression, particularly in children
- Nausea or vomiting
- Raised liver-enzyme results
- Skin rash
Get urgent medical advice
- Severe blistering or peeling skin reactions, including Stevens–Johnson syndrome, toxic epidermal necrolysis or DRESS
- Severe allergic reaction or respiratory depression
- Fever, rash, swollen glands or liver inflammation suggesting hypersensitivity syndrome
- Marked blood-cell abnormalities, with unexplained infection, bruising or bleeding
- New or worsening suicidal thoughts or behaviour
- Severe confusion, poor coordination or profound sedation
phenobarbital sodium in pregnancy
Exposure during pregnancy is associated with an increased risk of major congenital malformations, impaired fetal growth and possible adverse neurodevelopmental effects. Anyone planning pregnancy, pregnant or able to become pregnant needs specialist review. Do not stop antiseizure treatment suddenly because uncontrolled seizures can also cause serious harm. Discuss contraception and folic acid with the specialist: phenobarbital can reduce hormonal contraceptive effectiveness, and folic acid can affect phenobarbital concentrations.
phenobarbital sodium while breastfeeding
Phenobarbital enters breast milk and may sedate the infant; the oral-product information also identifies a small risk of methaemoglobinaemia. Breastfeeding is not recommended in the selected product information, and specialist advice is needed.
phenobarbital sodium interactions
Phenobarbital is a strong enzyme inducer with many clinically important interactions. Check all prescribed, non-prescribed and herbal products.
Alcohol and other central nervous system depressants
Can substantially increase sedation and respiratory depression; alcohol should be avoided.
Oestrogen- or progestogen-containing contraceptives
May reduce contraceptive effectiveness; discuss alternative contraception.
Common questions about phenobarbital sodium
Answers are fully visible for fast scanning and source review.
Does phenobarbital sodium treat absence seizures?
No. The selected products are licensed for epilepsy other than absence seizures, and the oral product information warns that absence seizures may be aggravated.
Why does phenobarbital sodium make people sleepy?
Its GABA-enhancing action reduces activity across the central nervous system as well as suppressing seizure activity.
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.