Phenobarbital Oral Dose for Epilepsy and Seizures
Phenobarbital guidance for tonic-clonic and focal epilepsy, with gradual titration and close safety monitoring.
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Source reviewed
October 2024
Guide category
Oral drugs
Safety boundary
Prescription medicine information for clinician-guided use.
Kenza Health Hub presents this medicine page as structured health education. Check dose, route, interactions, pregnancy or breast-feeding considerations, and local protocol with a qualified clinician or pharmacist. Read our medical editorial policy.
Quick clinical summary
| Item | Summary |
|---|---|
| Drug | Phenobarbital, also abbreviated PB |
| Class | Antiseizure medicine; barbiturate sedative |
| Common form | 60 mg tablet |
| Key use | Generalised tonic-clonic and focal seizures |
| Dose pattern | Start low, increase gradually according to response and tolerance |
| Stopping | Do not stop abruptly |
| Monitoring | Sedation, breathing risk, interactions, skin reactions, and seizure control |
Clinical context from Kenza
The sections below add practical explanation around the source-derived monograph. They are educational context and do not replace local protocols or clinician review.
Why phenobarbital dosing is gradual
Phenobarbital affects brain activity and can cause sedation, respiratory depression, and many medicine interactions. A gradual titration approach helps clinicians balance seizure control against adverse effects.
Why abrupt stopping matters
Stopping antiseizure treatment suddenly can worsen seizure control. This is why the source guidance says not to stop phenobarbital abruptly, even when changing to another antiseizure medicine.
Monitoring focus for long-term use
- Daytime drowsiness, dizziness, behaviour changes, and respiratory symptoms.
- Rash, fever, mouth ulcers, or bleeding, which require urgent medical review.
- Bone health, vitamin D status, pregnancy considerations, and interacting medicines.
Therapeutic action
Antiseizure (antiepileptic), sedative.
Indications
Epilepsy: generalised tonic-clonic seizures and focal (partial) seizures.
Forms and strengths
- 60 mg tablet.
Dose
Start with a low dose then increase gradually based on the patient's response and tolerance.
Due to the numerous and potentially severe adverse effects of PB, patients should be kept under close surveillance.
- Child 1 month to 11 years: start with 2 to 3 mg/kg once daily at bedtime or 1 to 1.5 mg/kg 2 times daily for 2 weeks; increase the daily dose by 1 to 2 mg/kg every week, up to 2 to 6 mg/kg once daily if necessary.
- Child 12 years and over and adult: start with 1 mg/kg, maximum 60 mg, once daily at bedtime for 2 weeks; increase the daily dose by 15 to 30 mg every week, up to 3 mg/kg once daily if needed, maximum 180 mg daily.
Duration
As long as required. Do not stop treatment abruptly, even if changing to another antiseizure medication.
Contra-indications, adverse effects, precautions
- Do not administer to patients with severe impairment of respiratory, renal, or hepatic function because of the risk of accumulation.
- Administer with caution in children, older patients, and patients with mild to moderate impairment of respiratory, renal, or hepatic function.
- May cause drowsiness, dizziness, headache, behavioural disturbances, respiratory depression, hypotension, vitamin D deficiency, osteoporosis, haematologic disorders, gastrointestinal disturbances, and rarely severe hypersensitivity reactions including Stevens-Johnson, Lyell, and DRESS syndromes.
- Early symptoms such as fever, rash, mouth ulcers, and bleeding require immediate medical attention.
- Avoid or monitor combination with mefloquine, drugs containing alcohol, benzodiazepines, opioid analgesics, antipsychotics, first-generation antihistamines, antidepressants, and other antiseizure medications.
- Use with extreme caution with benzodiazepines and opioid analgesics because of the increased risk of respiratory depression.
- PB may reduce the effect of many drugs including diazepam, midazolam, antimicrobials, some antiretrovirals, corticosteroids, tricyclic antidepressants, itraconazole, direct-acting antivirals for chronic hepatitis C, and warfarin. Adjust dosage if necessary.
- For implants and oral contraceptives, use injectable medroxyprogesterone or an intrauterine device.
- Avoid alcohol during treatment.
- Pregnancy: avoid because of the risk of facial and cardiac malformations, hypospadias, and small size for gestational age. If PB is the only option, use the lowest effective dose and administer folic acid 5 mg daily during the first trimester starting as early as possible.
- PB plasma concentrations may decrease during pregnancy. Monitor clinical response, increase dose if needed, then resume the usual dose after delivery. Monitor the child for a few days.
- Breast-feeding: administer with caution, reduce the dose if increased during pregnancy, and monitor the child for drowsiness, lethargy, and poor feeding.
- PB is not recommended for absence seizures because symptoms may worsen.
Frequently Asked Questions
Phenobarbital = PB oral dose and administration questions
What is phenobarbital oral used for?
This guide lists phenobarbital oral for epilepsy, including generalised tonic-clonic seizures and focal seizures.
What is the phenobarbital oral dose for children?
For children 1 month to 11 years, the guide starts with 2 to 3 mg/kg once daily at bedtime or 1 to 1.5 mg/kg twice daily for 2 weeks, then gradual weekly increases if needed.
What is the phenobarbital oral dose for adults?
For children 12 years and over and adults, the guide starts with 1 mg/kg, maximum 60 mg, once daily at bedtime for 2 weeks, then increases by 15 to 30 mg weekly if needed, up to 3 mg/kg once daily with a maximum of 180 mg daily.
Can phenobarbital be stopped abruptly?
No. The guide says treatment should not be stopped abruptly, even when changing to another antiseizure medication.
Source
MSF Essential drugs practical guidelines (January 2026)
This page combines source-derived medicine reference sections with Kenza editorial context, while leaving out the Storage and Remarks sections from the source batch.
Additional medical references
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