Nurses Compass
Drug Guide
Topiramate
Classification
Therapeutic: Anticonvulsant, for epilepsy and migraine prophylaxis
Pharmacological: Voltage-dependent sodium and calcium channel blocker; GABA enhancer
FDA Approved Indications
- Partial onset seizures in epilepsy
- Primary generalized tonic-clonic seizures
- Migraine prophylaxis
Mechanism of Action
Topiramate stabilizes neuronal membranes by blocking voltage-dependent sodium channels, enhancing GABA activity, and antagonizing glutamate receptors, leading to decreased neuronal excitability.
Dosage and Administration
Adult: Starting dose varies; typically 25-50 mg daily, titrated up to 100-200 mg daily divided in two doses.
Pediatric: Doses vary based on age and weight; typically initiated at 25-50 mg/day and titrated gradually.
Geriatric: Begin at lower doses due to potential for increased sensitivity and renal impairment, titrate cautiously.
Renal Impairment: Significant dose reduction required; dose adjustments based on renal function.
Hepatic Impairment: Use with caution; no specific dose adjustment indicated but monitor closely.
Pharmacokinetics
Absorption: Well absorbed from the gastrointestinal tract.
Distribution: Wide distribution; protein binding approximately 15%.
Metabolism: Minimal hepatic metabolism; mostly excreted unchanged.
Excretion: Primarily renal excretion; renal clearance is important.
Half Life: Approximately 20-30 hours, allowing once or twice daily dosing.
Contraindications
- Hypersensitivity to topiramate or any component.
- History of kidney stones.
Precautions
- Assess for renal stones, monitor for suicidal ideation, metabolic acidosis, increased intraocular pressure, visual disturbances, and cognitive dysfunction. Use with caution in pregnancy due to potential fetal harm.
Adverse Reactions - Common
- Paresthesia (Frequent)
- Weight loss (Common)
- Dizziness (Common)
- Fatigue (Common)
- Drowsiness (Common)
Adverse Reactions - Serious
- Acute myopia and secondary angle-closure glaucoma (Rare)
- Suicidal thoughts and behavior (Monitor closely)
- Metabolic acidosis (Uncommon)
- Kidney stones (Uncommon)
- Hypersensitivity reactions (Rare)
Drug-Drug Interactions
- Carbonic anhydrase inhibitors (e.g., acetazolamide)
- Oral contraceptives (may decrease effectiveness)
- Other CNS depressants
Drug-Food Interactions
N/ADrug-Herb Interactions
N/ANursing Implications
Assessment: Monitor renal function, serum bicarbonate, visual acuity, and mental health status.
Diagnoses:
- Risk for imbalanced fluid volume
- Risk for injury due to dizziness or cognitive impairment
- Ineffective coping related to side effects
Implementation: Administer with or without food, preferably twice daily. Educate patient about potential side effects and adherence.
Evaluation: Assess seizure control, decrease in migraine frequency, side effect profile, and laboratory parameters such as serum bicarbonate and renal function.
Patient/Family Teaching
- Take medication exactly as prescribed.
- Monitor for signs of metabolic acidosis, kidney stones, or visual changes.
- Maintain hydration to reduce kidney stone risk.
- Use caution when performing tasks requiring mental alertness.
- Do not stop medication abruptly.
Special Considerations
Black Box Warnings:
- Suicidal thoughts and behaviors.
- Eye effects (permanent vision loss, angle-closure glaucoma).
Genetic Factors: No specific genetic markers required for dosing but be aware of individual variability.
Lab Test Interference: May cause decreases in serum bicarbonate and urine pH; monitor accordingly.
Overdose Management
Signs/Symptoms: Drowsiness, speech disturbances, serious CNS depression, possible coma.
Treatment: Supportive care, activated charcoal if recent ingestion, monitor airway, breathing, circulation, and consider hemodialysis in severe cases.
Storage and Handling
Storage: Store at room temperature, 20-25°C (68-77°F). Protect from moisture and light.
Stability: Stable for approved shelf life, check manufacturer’s expiration date.