India · Neonatal Seizures · Paediatric Epilepsy · Loading Dose · Maintenance · TDM · Gardenal · Luminal
Therapeutic: 15–40 mg/L (mcg/mL)
Neonatal acute: 20–40 mg/L
Toxic: >40 mg/L (sedation)
Dangerous: >60 mg/L (resp. depression)
Steady state: ~2–3 weeks (adults), ~1 week neonates
| Indication / Patient | Loading dose | Maintenance dose | TDM target | Route |
|---|---|---|---|---|
| Neonatal seizures (term) | 20 mg/kg IV over 15–30 min | 3–5 mg/kg/day OD | 20–40 mg/L | IV → oral once tolerating feeds |
| Neonatal seizures (preterm) | 20 mg/kg IV over 20–30 min | 3–4 mg/kg/day OD | 20–40 mg/L | IV — specialist NICU |
| Neonatal refractory (2nd dose) | 10–20 mg/kg IV (if seizures persist at 30 min) | Same maintenance | 20–40 mg/L | Max total loading: 40 mg/kg |
| Paediatric epilepsy | Not usually needed | 3–5 mg/kg/day OD at bedtime | 15–40 mg/L | Oral (once daily — long t½) |
| Status epilepticus (2nd/3rd line) | 15–20 mg/kg IV at 1 mg/kg/min | Specialist directed | 15–40 mg/L | IV — ICU only, resp. support |
| Adult epilepsy | Not usually needed | 60–180 mg OD at bedtime | 15–40 mg/L | Oral once daily |
Phenobarbitone (phenobarbital) remains the first-line drug for neonatal seizures in India and in most low-to-middle income country settings, recommended by the WHO and the National Neonatology Forum (NNF) India. It works by enhancing GABA-A receptor-mediated inhibition and reducing glutamate-mediated excitation, producing broad-spectrum anticonvulsant activity. Despite evidence that levetiracetam and phenytoin may be effective alternatives, phenobarbitone retains its first-line status in Indian NICUs due to its low cost, widespread availability, and decades of clinical familiarity.
The loading dose for neonatal seizures is 20 mg/kg IV, infused slowly over 15–30 minutes. Using Gardenal 200mg/ml injection: for a 3000g (3 kg) neonate at 20 mg/kg = 60 mg = 0.3 ml of 200mg/ml solution. This must be diluted — never give concentrated phenobarbitone undiluted IV. Dilute to 1–2 mg/ml with 5% glucose or normal saline before infusion. Monitor heart rate, respiratory rate, and oxygen saturation continuously during infusion — apnoea and bradycardia are the most serious acute adverse effects. Bag and mask ventilation must be immediately available.
If seizures persist 30 minutes after the initial 20 mg/kg loading dose, an additional dose of 10–20 mg/kg IV may be given, to a maximum cumulative loading dose of 40 mg/kg. Beyond this, second-line agents (phenytoin or levetiracetam) should be added. Respiratory depression risk increases significantly with cumulative doses above 30–40 mg/kg.
Maintenance dosing begins 12–24 hours after the loading dose. Start at 3–5 mg/kg/day as a single daily dose. In preterm neonates and those with renal or hepatic impairment, start at the lower end (3 mg/kg/day) and titrate based on TDM. The extremely long half-life in neonates (up to 200 hours in preterm infants) means once-daily dosing is appropriate and that dose changes take up to a week to reach a new steady state. Transition to oral phenobarbitone elixir (20mg/5ml) once the neonate is tolerating feeds and IV access is no longer needed.
In neonates: check a trough serum phenobarbitone level 24 hours after loading (before first maintenance dose) to confirm levels are within therapeutic range (20–40 mg/L for acute neonatal seizure control). Recheck 5–7 days after any dose change. Target levels for ongoing neonatal seizure suppression: 20–40 mg/L. Levels >40 mg/L cause excessive sedation and apnoea; >60 mg/L is life-threatening. For children on maintenance therapy for epilepsy: check trough levels (pre-morning dose) after steady state is reached (~2–3 weeks in children) with a target of 15–40 mg/L, guided by seizure control and tolerance. Most Indian tertiary hospitals can perform phenobarbitone assays by ELISA or immunoassay.