phenobarbital at a glance
Class
Barbiturate antiseizure treatment
Licensed role
Epilepsy, except absence seizures
Administration
Taken by mouth; follow the prescription label
Liquid safety
Confirm the exact formulation before supply or administration; liquids differ in concentration and ethanol content
What is phenobarbital used for?
The selected oral elixir is licensed as an anticonvulsant.
Treatment of all forms of epilepsy except absence seizures.
How does phenobarbital work?
Phenobarbital strengthens inhibitory signalling through GABA-A receptors, making neurons less likely to fire repeatedly. This raises the seizure threshold and limits seizure spread, but can also cause sedation and respiratory depression at excessive exposure.
How to take phenobarbital
Take the elixir by mouth exactly as directed on the prescription label. Confirm the intended liquid formulation and do not switch products without professional review. Avoid alcohol and do not stop phenobarbital suddenly, as withdrawal can provoke seizures.
Check the medicine name and formulation with each new supply.
Do not share phenobarbital with anyone else.
Do not drive or operate machinery if drowsy, dizzy or otherwise impaired.
phenobarbital side effects
Common or expected effects
- Drowsiness or sedation
- Lethargy or dizziness
- Unsteadiness or impaired coordination
- Memory, concentration or cognitive difficulties
- Behavioural changes, including irritability or paradoxical excitement
Get urgent medical advice
- Severe skin reactions with blistering, peeling or mouth ulcers
- Hypersensitivity syndrome with fever, rash, swollen glands or organ involvement
- Respiratory depression or profound sedation
- Hepatitis, cholestasis or jaundice
- Blood disorders causing infection, mouth ulcers, bruising or bleeding
- Suicidal thoughts or behaviour
phenobarbital in pregnancy
Phenobarbital exposure during pregnancy is associated with increased risks of congenital malformations, impaired fetal growth and possible adverse neurodevelopmental effects. Anyone planning pregnancy, pregnant or possibly pregnant needs prompt specialist review, but phenobarbital must not be stopped suddenly because uncontrolled seizures can harm both parent and baby. Phenobarbital can also reduce the effectiveness of hormonal contraception.
phenobarbital while breastfeeding
Phenobarbital passes into breast milk. The selected product information advises against breastfeeding because of possible infant sedation and methaemoglobinaemia; feeding plans should be reviewed with the epilepsy and maternity teams without abruptly stopping treatment.
phenobarbital interactions
Phenobarbital induces hepatic enzymes and can lower the effectiveness of many medicines. Sedating combinations can also intensify central nervous system and respiratory depression.
Alcohol, opioids, sedatives and sedating antihistamines
May cause additive drowsiness and potentially serious respiratory depression; alcohol should be avoided.
Oestrogen- or progestogen-containing contraception
Accelerated hormone metabolism may cause contraceptive failure or breakthrough bleeding; alternative contraception requires professional discussion.
Coumarin anticoagulants such as warfarin
Accelerated metabolism may reduce anticoagulant effect, requiring clinical and laboratory review.
Common questions about phenobarbital
Answers are fully visible for fast scanning and source review.
Can phenobarbital treat absence seizures?
No. The selected elixir is licensed for epilepsy other than absence seizures.
Can phenobarbital be stopped suddenly?
No. Abrupt withdrawal can cause severe withdrawal symptoms and a return or worsening of seizures; changes require prescriber supervision.
Does phenobarbital cause drowsiness?
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.