Description

Phenobarbital Tablets: Comprehensive Product Description

Phenobarbital is a long-acting barbiturate primarily utilized for its anticonvulsant and sedative properties. As a central nervous system (CNS) depressant, it plays a pivotal role in managing various seizure disorders and providing sedation in specific medical contexts.

Chemical Composition and Properties

• Chemical Name: 5-Ethyl-5-phenylbarbituric acid
• Molecular Formula: C₁₂H₁₂N₂O₃
• Molecular Weight: 232.24 g/mol
• Physical Appearance: White, odorless, crystalline powder
• Solubility: Slightly soluble in water; soluble in alcohol and ether; sparingly soluble in chloroform

Pharmacodynamics and Mechanism of Action

Phenobarbital enhances the inhibitory neurotransmitter gamma-aminobutyric acid (GABA) by binding to GABA_A receptors, leading to increased chloride ion influx and neuronal hyperpolarization. This action elevates the seizure threshold and diminishes the spread of seizure activity, making it effective in controlling various types of seizures.

Pharmacokinetics

• Absorption: Approximately 70–90% absorbed when administered orally, with peak plasma concentrations reached within 8–12 hours.
• Distribution: Widely distributed throughout body tissues; crosses the blood-brain barrier and placenta.
• Metabolism: Metabolized primarily in the liver via hydroxylation.
• Elimination Half-Life: Ranges from 53 to 118 hours in adults, indicating prolonged action.
• Excretion: Excreted mainly via urine, with 25–50% as unchanged drug.

Indications

Phenobarbital tablets are indicated for:

• Seizure Disorders: Management of generalized tonic-clonic (grand mal) and partial seizures.
• Sedation: Short-term treatment of insomnia and preoperative sedation.
• Off-Label Uses: Occasionally used in the management of alcohol withdrawal symptoms and hyperbilirubinemia in neonates.

Dosage Forms and Strengths

Phenobarbital tablets are available in various strengths to accommodate individualized dosing requirements:

Strength (mg)	Imprint Code	Color	Shape	NDC Code
15	WW 445	White	Round	0143-1445
30	WW 450	White	Round	0143-1450
60	WW 455	White	Round	0143-1455
100	WW 460	White	Round	0143-1460

Dosage and Administration

• Adults:
  • Seizure Control: 60–200 mg daily, administered in divided doses.
  • Sedation: 30–120 mg daily, given in divided doses.
• Pediatric Patients:
  • Seizure Control: 3–6 mg/kg/day, administered in divided doses.

Special Populations

• Hepatic Impairment: Dose adjustments may be necessary due to reduced metabolism.
• Renal Impairment: Caution advised; monitor for signs of toxicity.

Contraindications

• Hypersensitivity to phenobarbital or other barbiturates.
• Severe respiratory insufficiency.
• History of acute intermittent porphyria.

Warnings and Precautions

• CNS Depression: May impair mental and/or physical abilities; caution patients against engaging in hazardous activities requiring mental alertness, such as operating machinery or driving.
• Dependence and Abuse Potential: Prolonged use can lead to physical dependence; monitor for signs of misuse or abuse.
• Withdrawal Symptoms: Abrupt discontinuation may precipitate withdrawal symptoms; taper dosage gradually under medical supervision.
• Suicidal Ideation: Monitor for emergence or worsening of depression, suicidal thoughts, or behavior.

Adverse Reactions

Common adverse reactions include:

• Drowsiness
• Dizziness
• Nausea
• Vomiting
• Headache

Serious adverse reactions may include:

• Respiratory depression
• Hypotension
• Stevens-Johnson syndrome
• Agranulocytosis

Drug Interactions

Phenobarbital is a potent inducer of hepatic enzymes and may interact with various medications:

• Anticoagulants: May decrease the efficacy of warfarin.
• Oral Contraceptives: May reduce contraceptive effectiveness; advise alternative contraceptive measures.
• CNS Depressants: Concomitant use with other CNS depressants (e.g., alcohol, benzodiazepines) can enhance sedative effects; use with caution.

Monitoring Parameters

• Regular monitoring of serum phenobarbital levels to ensure therapeutic concentrations (typically 15–40 mcg/mL).
• Periodic liver function tests due to hepatic metabolism.
• Complete blood counts to detect potential hematologic adverse effects.

 Phenobarbital is a prescription medication used primarily for the treatment of seizures, insomnia, and as a sedative before medical procedures. As a barbiturate, Phenobarbital works by depressing the central nervous system, leading to a calming effect on the brain and body. It is often used for its ability to prevent or control seizures in patients with epilepsy and to help manage symptoms of anxiety and insomnia.

Nembutal is also used in some cases for sedation in surgical or diagnostic procedures. Due to its potency and potential for dependence, this medication should be taken only under the supervision of a healthcare provider. Long-term use may lead to tolerance, dependence, or withdrawal symptoms. It is available in tablet form and must be used according to a doctor’s instructions.