Top 300 Pharmacy Drug Cards

PHENOBARBITAL: Luminal, Various

Class: Long-Acting Barbiturate. C-IV

Dosage Forms. Tablet: 15 mg, 16.2 mg, 30 mg, 32.4 mg, 60 mg, 64.8 mg, 97.2 mg, 100 mg; Elixir, Solution: 20 mg/5 mL; Solution: 20 mg/5 mL


Common FDA Label Indication, Dosing, and Titration.

1. Epilepsy: Adults, 50-100 mg po bid-tid; Children, 15-50 mg po bid-tid (tablet) or 3-6 mg/kg/d po (solution)

2. Daytime sedation: Adults, 30-120 mg po divided into 2-3 doses, may titrate to 400 mg/d; Children, 6 mg/kg/d po divided into 3 doses

3. Sleep: Adults, 100-320 mg po as single dose

Off-Label Uses. None

MOA. Phenobarbital produces all degrees of depression of the central nervous system, from sedation to general anesthesia. Has been demonstrated to depress monosynaptic responses in the central nervous system only transiently, but synaptic recovery is delayed and a decrease in postsynaptic resistance is observed at some synapses.

Drug Characteristics: Phenobarbital


Medication Safety Issues: Phenobarbital


Drug Interactions: Phenobarbital


Adverse Reactions: Phenobarbital


Efficacy Monitoring Parameters. Control of seizures, achieving adequate sleep; phenobarbital serum levels: therapeutic 10-40 mcg/mL; toxic >40 mcg/mL.

Toxicity Monitoring Parameters. SCr, LFTs, and CBC annually.

Key Patient Counseling Points. Avoid activities requiring mental alertness or coordination until drug effects are realized, as drug may cause dizziness, light-headedness, or somnolence. Advise patient against sudden discontinuation of drug. Do not drink alcohol or use other CNS depressant drugs while taking phenobarbital. Many drug interactions; check with pharmacist when starting new medications or OTC products.

Clinical Pearls. Efficacy for inducing and maintaining sleep begins to decline after approximately 2 wk; should not be used long term. Avoid use in children and elderly who are at higher risk of toxicity. Avoid abrupt withdrawal to avoid risk of seizures.

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