Phenobarbital
Pronouncation: (fee-no-BAR-bih-tahl)Class: Barbiturate, long-acting, Sedative and hypnotic Phenobarbital
Trade Names:
Solfoton
- Tablets 16 mg
- Capsules 16 mg
Trade Names:
Luminal Sodium
- Injection 130 mg/mL
Pharmacology
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Depresses sensory cortex, decreases motor activity, alters cerebellar function and produces drowsiness, sedation, and hypnosis.
Pharmacokinetics
Absorption
The T max is 8 to 12 h (oral).
Distribution
Rapidly distributed to all tissues and fluids with high concentrations in the brain, liver, and kidneys. Lipid solubility plays a dominant factor in distribution. Protein binding is 20% to 45%.
Metabolism
Detoxified in liver by microsomal enzyme system.
Elimination
Eliminated in urine (25% to 50% as unchanged), and small amount in the feces. The t ½ plasma is 53 to 118 h (adults), 60 to 180 h (children).
Onset
Onset of action is 30 min.
Duration
Duration is 5 to 6 h (oral).
Indications and Usage
Short-term treatment of insomnia; long-term treatment of generalized tonic-clonic and cortical focal seizures; emergency control of acute convulsions; preanesthetic sedation.
Unlabeled Uses
Treatment of febrile seizures in children; treatment and prevention of hyperbilirubinemia in newborns; management of chronic cholestasis.
Contraindications
Hypersensitivity to barbiturates; history of addiction to sedative/hypnotic drugs; history of porphyria; severe liver impairment; respiratory disease with dyspnea; nephritic patients.
Dosage and Administration
InsomniaAdults
PO / IM / IV 100 to 320 mg.
SedationAdults
PO 30 to 120 mg/day in 2 to 3 divided doses.
EpilepsyAdults
PO 60 to 250 mg/day.
ConvulsionsAdults
IV 100 to 320 mg. Repeat if needed (max, 600 mg per 24 h).
Status EpilepticusAdults
IV 10 to 20 mg/kg. Repeat if needed.
ChildrenIV 15 to 20 mg/kg over 10 to 15 min.
Preoperative SedationChildren
PO / IM / IV 1 to 3 mg/kg.
AnticonvulsantChildren
IM / IV 4 to 6 mg/kg/day. For 10ߙdays, then adjust to blood level. Alternatively, use IM / IV 10 to 15ߙmg/kg/day to reach therapeutic level more quickly. Max IV rate 60ߙmg/min. Max adult IM dose is 500ߙmg or 5 mL volume regardless of concentration.
General Advice
- For oral administration, tablets may be crushed and mixed with fluid or food.
- For IM administration, inject deeply into large muscle. Do not exceed max IM dose of 500 mg or 5 mL of volume (regardless of concentration).
- For IV administration, inject into large vein. Do not exceed max IV rate of 60ߙmg/min; respiratory depression, apnea and hypotension may result.
- Avoid inadvertent intra-arterial injection; arterial spasm, thrombosis, and gangrene may result.
Storage/Stability
Store at room temperature. Protect from light.
Drug Interactions
Alcohol, CNS depressantsMay enhance CNS depressant effects.
Anticoagulants (eg, warfarin), beta-blockers (eg, metoprolol, propranolol), doxycycline, metronidazole, quinidine, theophyllines, verapamilActivity of these drugs may be reduced.
AnticonvulsantsSerum concentrations of carbamazepine, valproic acid and succinimides may be reduced. Valproic acid may increase barbiturate serum levels.
CorticosteroidsMay reduce effectiveness of corticosteroids.
Estrogens, estrogen-containing oral contraceptivesMay reduce contraceptive effectiveness.
PhenytoinMay increase phenobarbital levels while phenytoin levels may increase or decrease.
Laboratory Test Interactions
May cause decreased serum bilirubin concentrations; false-positive phentolamine test results; decreased response to metyrapone; impaired absorption of radioactive cyanocobalamin.
Adverse Reactions
Cardiovascular
Bradycardia; hypotension; syncope.
CNS
Drowsiness; agitation; confusion; anxiety; headache; hyperkinesia; ataxia; CNS depression; paradoxical excitement; nightmares; psychiatric disturbances; hallucinations; insomnia; dizziness.
GI
Nausea; vomiting; constipation.
Hematologic
Blood dyscrasias (eg, agranulocytosis, thrombocytopenia).
Hepatic
Liver damage.
Respiratory
Hypoventilation; apnea; laryngospasm; bronchospasm.
Miscellaneous
Hypersensitivity reactions (eg, angioedema, rashes, exfoliative dermatitis); fever; injection-site reactions (eg, local pain, thrombophlebitis).
Precautions
Pregnancy
Category D .
Lactation
Excreted in breast milk.
Children
May respond with excitement rather than depression.
Elderly
More sensitive to drug effects; dosage reduction is required.
Renal Function
Use drug with caution; dosage reduction may be required.
Hepatic Function
Use drug with caution; dosage reduction may be required.
Abuse
Administer drug with caution to patients with history of drug abuse.
Debilitated patients
Use drug with extreme caution.
Dependence
Tolerance or psychologic and physical dependence may occur with continued use.
Seizure disorders
Status epilepticus may result from abrupt discontinuation.
Overdosage
Symptoms
CNS and respiratory depression, Cheyne-Stokes respiration, areflexia, constriction of pupils, oliguria, tachycardia, hypotension, lowered body temperature, coma, shock syndrome, pneumonia, pulmonary edema, cardiac arrhythmias, CHF, renal failure.
Patient Information
- Advise patient to increase intake of vitamin D-fortified foods (eg, milk products) while taking this medication.
- Explain the following importances of maintaining adequate intake of folic acid: fresh vegetables, fruits, whole grains, liver.
- Instruct patient to report the following symptoms to health care provider: nausea, vomiting, drowsiness, dizziness, fever, sore throat, mouth sores or easy bleeding or bruising.
- Caution patient to avoid intake of alcoholic beverages or other CNS depressants.
- Warn patient that medication may be habit forming, and for that reason, it is important to take medicine as directed.
- Advise patient that drug may cause drowsiness, and to use caution while driving or performing other tasks requiring mental alertness.
- Instruct patient not to stop taking medication abruptly without consulting health care provider.
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More Phenobarbital resources:
Phenobarbital - Includes detailed dosage instructions.
Phenobarbital Drug Interactions
Sedation, Seizures, Insomnia, Hyperbilirubinemia
