- Drugs List
- Therapeutic Indications
- Precautions and Warnings
- Pregnancy and Lactation
- Side Effects
Oral formulations containing phenobarbital.
Epilepsy - except absence seizures
Adjust dose to meet the needs of the patient to achieve adequate control of seizures; this usually required plasma concentrations of 15 to 40mg per litre (60 to 170micromol per litre).
Tablets: 60 to 180mg at night.
Elixir: 60 to 200mg daily in two to three divided doses.
As clearance diminishes in the elderly, the dose is usually lower.
Tablets: 5 to 8mg/kg daily.
Elixir: 3 to 6mg/kg daily in two to three divided doses.
The following alternative dosing schedule may be suitable for children aged 1 month to 12 years:
Initially 1 to 1.5mg/kg twice daily, increased by 2mg/kg daily as required.
The usual maintenance dose is 2.5 to 4mg/kg once to twice daily.
Severe respiratory depression
Severe renal impairment
Severe hepatic disorder
Precautions and Warnings
History of drug misuse
History of alcohol abuse
Glucose-galactose malabsorption syndrome
Children under 18 years
Do not withdraw this drug suddenly
Advise impaired alertness may affect ability to drive or operate machinery
Pregnancy: Administer vitamin K in the last few weeks of pregnancy
Prolonged or excessive use may result in dependence
Tolerance may develop with continued use
Patients at risk of suicide should be closely supervised
Advise patient not to take St John's wort concurrently
Folic acid 5mg daily required pre-conception to end of 1st trimester
Rebound effect may occur after cessation of treatment
Hyperactivity may be exacerbated
Increased risk of osteomalacia; consider vitamin D supplement
May affect results of some laboratory tests
Some formulations contain lactose
Advise patients/carers to seek medical advice if suicidal intent develops
Neonate exposed in utero: Administer vitamin K at birth
Prescribe by manufacturer's product to ensure seizure control maintenance
Monitor for Antiepileptic Hypersensitivity Syndrome
Discontinue immediately if Antiepileptic Hypersensitivity Syndrome occurs
Advise patient to avoid alcohol during treatment
Advise patient to monitor for and report any skin changes
Suspend treatment if Stevens-Johnson syndrome is suspected
Suspend treatment if toxic epidermal necrolysis is suspected
Pregnancy and Lactation
Use phenobarbital with caution during pregnancy.
The manufacturer advises caution if phenobarbital is used during pregnancy. Available reports indicate a risk of teratogenic effects, this appears to be greater if more than one antiepileptic drug is administered.
Phenobarbital is contraindicated during breastfeeding.
The manufacturer does not recommend breastfeeding whilst taking phenobarbital. Phenobarbital is present in human breast milk and there is a small risk of neonatal sedation.
Mental status changes
Allergic skin reactions
Toxic epidermal necrolysis
Fixed drug eruption
Purpura exfoliative dermatitis
Liver function disturbances
Disturbed vitamin D metabolism
Metabolic bone disease
Effects on Laboratory Tests
Phenobarbital may interfere with some laboratory tests including metyrapone test, phentolamine tests and serum bilirubin estimation.
It is strongly recommended that the UK National Poisons Information Service be consulted on cases of suspected or actual overdose where there is doubt over the degree of risk or about appropriate management.
The following number will direct the caller to the relevant local centre (0844) 892 0111
Information may be obtained if you have access to ToxBase the primary clinical toxicology database of the National Poisons Information Service. This is available via password on the internet ( www.toxbase.org ) or if this is unavailable at the backup site ( www.toxbasebackup.org ).
Last Full Review Date: December 2019
Summary of Product Characteristics: Phenobarbital 15mg tablets. Accord UK Ltd. Revised February 2019.
Summary of Product Characteristics: Phenobarbital 30mg tablets. Accord UK Ltd. Revised February 2019.
Summary of Product Characteristics: Phenobarbital 60mg tablets. Accord UK Ltd. Revised February 2019.
Summary of Product Characteristics: Phenobarbital 60mg tablets. Teva UK Ltd. Revised January 2018.
Summary of Product Characteristics: Phenobarbital 15mg tablets. Bristol Laboratories Ltd. Revised September 2018.
Summary of Product Characteristics: Phenobarbital 30mg tablets. Bristol Laboratories Ltd. Revised September 2018.
Summary of Product Characteristics: Phenobarbital 60mg tablets. Bristol Laboratories Ltd. Revised September 2018.
Summary of Product Characteristics: Phenobarbital elixir. Thornton and Ross. Revised January 2016.
NICE Evidence Services Available at: www.nice.org.uk Last accessed: 11 November 2019
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Medscape UK | Univadis prescription drug monographs & interactions are based on FDB Multilex Content
FDB Disclaimer : FDB Multilex is intended for the use of healthcare professionals and is provided on the basis that the healthcare professionals will retain FULL and SOLE responsibility for deciding what treatment to prescribe or dispense for any particular patient or circumstance.