Generic Name

Lamotrigine

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Classification

FDA Approved Indications

• Bipolar I disorder maintenance therapy
• Partial seizures
• Generalized seizures (including primary generalized tonic-clonic seizures)

Mechanism of Action

Lamotrigine stabilizes neuronal membranes by inhibiting voltage-sensitive sodium channels, which decreases the release of excitatory neurotransmitters like glutamate and aspartate, thereby exerting anticonvulsant and mood-stabilizing effects.

Dosage and Administration

Adult: Initial dose typically 25 mg once daily for 2 weeks, then titrated gradually based on response and tolerability.

Pediatric: Starting dose generally 0.3 mg/kg/day, titrated gradually.

Geriatric: Start at lower doses; titrate cautiously due to potential for increased sensitivity.

Renal Impairment: Adjust dose based on renal function; consult detailed dosing guidelines.

Hepatic Impairment: Use with caution; no specific dose adjustment provided, but monitor closely.

Pharmacokinetics

Absorption: Rapid and complete absorption from gastrointestinal tract.

Distribution: Approximately 55% bound to plasma proteins.

Metabolism: Metabolized mainly via conjugation with glucuronic acid; minimal hepatic oxidation.

Excretion: Excreted primarily in urine as metabolites.

Half Life: Approximately 25-33 hours in healthy adults; shorter in children.

Contraindications

• Hypersensitivity to lamotrigine or other ingredients.
• History of severe hypersensitivity reactions such as Stevens-Johnson syndrome.

Precautions

• Risk of aseptic meningitis; monitoring required.
• History of mood disorders or suicidality; caution advised.
• Use with caution in patients with kidney or liver impairment.
• Potential for serious skin reactions; initiate at low doses and titrate slowly.

Adverse Reactions - Common

• Dizziness (Common)
• Headache (Common)
• Nausea (Common)
• Somnolence (Common)
• Rash (Uncommon)

Adverse Reactions - Serious

• Stevens-Johnson syndrome (SJS) (Rare)
• Toxic epidermal necrolysis (TEN) (Rare)
• Aseptic meningitis (Rare)
• Blood dyscrasias (Rare)
• Suicidal thoughts or behavior (Potentially increased)

Drug-Drug Interactions

• Valproic acid (increases lamotrigine levels, risk of SJS)
• Oral contraceptives (may decrease lamotrigine levels)
• Carbamazepine (may decrease lamotrigine levels)
• Other enzyme inducers or inhibitors

Drug-Food Interactions

N/A

Drug-Herb Interactions

N/A

Nursing Implications

Patient/Family Teaching

• Take medication exactly as prescribed.
• Report any skin rash, fever, sore throat, or blisters immediately.
• Do not stop medication abruptly.
• Use caution when operating machinery until response is known.
• Inform about potential mood changes and suicidal thoughts.

Special Considerations

Black Box Warnings:

• Serious dermatologic reactions such as Stevens-Johnson syndrome and toxic epidermal necrolysis

Genetic Factors: HLA-B extsuperscript*1502 allele may increase risk of SJS in some populations (e.g., Asians).

Lab Test Interference: May affect some laboratory tests, such as blood counts.

Overdose Management

Signs/Symptoms: Dizziness, ataxia, nystagmus, altered mental status.

Treatment: Supportive care; consider activated charcoal if ingestion is recent; hemodialysis may reduce plasma levels in overdose.

Storage and Handling

Storage: Stored at room temperature, 20-25°C (68-77°F).

Stability: Stable up to the expiration date when stored properly.