Phenobarbital (Phenobarbitone) Pediatric Dose Calculator

Weight-based phenobarbital dosing for children — 3–6 mg/kg/day once daily · max 180 mg/day. Enter age and weight for the dose in mg and syrup mL, tablets or injection volume.

Category: NeurologyAges: Birth – adultUpdated: 2026-09-27For: cliniciansEmergency useHospital use

Pediatric dosing

Seizures / status epilepticus — IV loading dose Emergency

15–20 mg/kg/dose · single loading dose over ≥20 minutes (max 1 mg/kg/min) · max 1 g/dose

Duration: Once · Neonatal seizures: a further 10–20 mg/kg may be given if seizures persist (total 40 mg/kg) — neonatal unit protocol.

Have airway support and bag-valve-mask ready (respiratory depression, especially after benzodiazepines).

Neonatal seizures — maintenance Hospital

3–5 mg/kg/day once daily — once daily, starting 12–24 hours after the loading dose

Duration: Review need regularly; stop when seizure-free per unit protocol

Eligibility: ≤28 days

Epilepsy — oral maintenance

3–6 mg/kg/day once daily · max 180 mg/day — once daily at night (or in two divided doses)

Duration: Long term — do not stop abruptly · Start low and titrate; target the lowest dose that controls seizures.

Eligibility: ≥1 month

Phenobarbital (phenobarbitone) dose chart by age and weight

Epilepsy — oral maintenance. Weights are WHO/IAP reference medians for age — always dose on the measured weight.

Computed with the PediaRx dose engine from the regimen above; caps and age limits applied.
Age	Weight	Dose (mg)	Syrup 20 mg/5 mL	Frequency
15 days	3.8 kg	Below minimum age
1 month	4.3 kg	21.5 mg	5.4 mL	Once daily at night (or in two divided doses)
3 months	6.1 kg	30.5 mg	7.6 mL	Once daily at night (or in two divided doses)
6 months	7.6 kg	38 mg	9.5 mL	Once daily at night (or in two divided doses)
9 months	8.6 kg	43 mg	11 mL	Once daily at night (or in two divided doses)
1 year	9.3 kg	46.5 mg	11.5 mL	Once daily at night (or in two divided doses)
18 months	10.6 kg	53 mg	13.5 mL	Once daily at night (or in two divided doses)
2 years	11.8 kg	59 mg	15 mL	Once daily at night (or in two divided doses)
3 years	14.1 kg	70.5 mg	17.5 mL	Once daily at night (or in two divided doses)
4 years	16.2 kg	81 mg	20.5 mL	Once daily at night (or in two divided doses)
5 years	17.5 kg	87.5 mg	22 mL	Once daily at night (or in two divided doses)
6 years	19 kg	95 mg	24 mL	Once daily at night (or in two divided doses)
8 years	24.4 kg	122 mg	30.5 mL	Once daily at night (or in two divided doses)
10 years	31.1 kg	155.5 mg	39 mL	Once daily at night (or in two divided doses)
12 years	39.4 kg	180 mg	45 mL	Once daily at night (or in two divided doses)

Strengths in the calculator

Injection 200 mg/mL (dilute 1 in 10 with water for injection before IV use) (Intravenous / Intramuscular)
Syrup 20 mg/5 mL (Oral)
Tablet 30 mg (Oral)
Tablet 60 mg (Oral)

Different strength on your bottle? Use “Different strength on the bottle?” under the result.

Safety

Contraindications and cautions

Acute porphyria; severe respiratory depression.

Pregnancy and breastfeeding

Legacy FDA category D. Teratogenic risk; continue if needed for seizure control under specialist care (give folic acid, neonatal vitamin K).

Can sedate the infant — monitor.

Clinical notes

Controlled drug. Enzyme inducer with many interactions. Never stop abruptly (withdrawal seizures).

Adult and adolescent (≥40 kg) dose

60–180 mg — Once daily at night (individualised) (max 180 mg per dose, 180 mg per day).

Other names and brands

Also known as Phenobarbitone, Phenobarbital, Luminal.

India: Gardenal

Brand examples only — products and strengths vary by country. Always check the label.

Frequently asked questions

What is the phenobarbital dose for children?

Epilepsy — oral maintenance: 3–6 mg/kg/day once daily · max 180 mg/day. Usual duration: Long term — do not stop abruptly. Always use the child's measured weight and check the strength on the bottle.

How many mL of syrup 20 mg/5 mL for an 11.8 kg child?

For epilepsy — oral maintenance, an 11.8 kg child (about 2 years) needs 59 mg per dose — 15 mL of Syrup 20 mg/5 mL, once daily at night (or in two divided doses). Recalculate with the child's actual weight.

From what age can phenobarbital be given?

Age range in PediaRx: Birth – adult. Each indication can have its own age and weight limits, shown with its regimen.

Is phenobarbital safe in pregnancy?

Legacy FDA category D. Teratogenic risk; continue if needed for seizure control under specialist care (give folic acid, neonatal vitamin K).

Sources and editorial process

Guidelines on neonatal seizures (2011) — World Health Organization
Evidence-based guideline: treatment of convulsive status epilepticus in children and adults (Glauser et al., Epilepsy Curr 2016) — American Epilepsy Society
BNF for Children — Phenobarbital — NICE / BMJ Group / Royal Pharmaceutical Society

Dosing data last updated 2026-09-27. PediaRx is built and maintained by Dr. Shounak Pal, MBBS (Medical Officer, Government of West Bengal, India — founder and developer of PediaRx). Every regimen is encoded with explicit units, maximum doses and age/weight limits and is checked by automated tests before publication. Report an error: hello@pediarx.com.

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Clinical disclaimer: reference tool for qualified health professionals. Verify every dose against current guidance and the product label before prescribing.

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