Topamax

— THERAPEUTIC CATEGORIES —
  • Migraine and headache
  • Seizure disorders
PAGE CONTENTS
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  • Generic Name & Formulations
  • Indications
  • Dosage and Administration
  • Contraindications
  • Boxed Warnings
  • Warnings/Precautions
  • Pharmacokinetics
  • Interactions
  • Adverse Reactions
  • Clinical Trials
  • Note
  • Patient Counseling

    • Topamax Generic Name & Formulations

    Legal Class

    Rx

    General Description

    Topiramate 25mg, 50mg, 100mg, 200mg; tabs.

    Pharmacological Class

    Sulfamate.

    See Also

    How Supplied

    Tabs, Caps—60

    Manufacturer

    Janssen Pharmaceuticals, Inc.

    Generic Availability

    YES

    Mechanism of Action

    Topiramate blocks voltage-dependent sodium channels, augments the activity of the neurotransmitter gamma-aminobutyrate at some subtypes of the GABA-A receptor, antagonizes the AMPA/kainate subtype of the glutamate receptor, and inhibits the carbonic anhydrase enzyme, particularly isozymes II and IV.

    Topamax Indications

    Indications

    Migraine prophylaxis. Not been studied for use in acute treatment of migraines.

    Topamax Dosage and Administration

    Adult

    May swallow caps whole or sprinkle contents onto soft food (swallow immediately). Give in two equally divided doses. Titrate at 1-week intervals to target dose of 100mg/day. Initially 25mg once daily in the PM, then 25mg twice daily, then 25mg in the AM and 50mg in the PM, then 50mg twice daily. Renal impairment (CrCl <70mL/min): reduce dose by ½. Hemodialysis: may need extra dose.

    Children

    <12yrs: not established.

    Administration

    Do not break tablets (bitter taste).

    Nursing Considerations

    Do not break tablets (bitter taste). Counsel patients on effective birth control (potential decrease in efficacy with estrogen-containing birth control). Unexplained lethargy, vomiting, or changes in mental status may be symptoms of hyperammonemic encephalopathy. Watch for signs of decreased sweating and fever.

    Topamax Contraindications

    Not Applicable

    Topamax Boxed Warnings

    Not Applicable

    Topamax Warnings/Precautions

    Warnings/Precautions

    Discontinue if acute myopia and secondary angle-closure glaucoma syndrome occur. Consider discontinuing if visual field defects occur. Kidney stones. Maintain adequate hydration; avoid ketogenic diets. Measure serum bicarbonate at baseline, then periodically during therapy; consider reducing dose or discontinuing if metabolic acidosis develops and persists. Inborn errors of metabolism or reduced hepatic mitochondrial activity: increased risk of hyperammonemia; measure ammonia levels if encephalopathic symptoms occur. Monitor on growth (during prolonged therapy), oligohidrosis, and hyperthermia esp. in children. Suicidal tendencies (monitor). Discontinue at the 1st sign of a rash. Avoid abrupt cessation. Hepatic or renal impairment. Elderly. Fetal toxicity (eg, congenital malformations, oral clefts, small for gestational age). Labor & delivery. Pregnancy. Advise females of reproductive potential to use effective contraception during therapy. Nursing mothers.

    Topamax Pharmacokinetics

    Absorption

    • Peak plasma concentrations occurred at approximately 2 hours following a 400mg oral dose.

    Distribution

    • 15–41% plasma protein bound.

    Metabolism

    • Hepatic (minor). Metabolites are formed via hydroxylation, hydrolysis, and glucuronidation.

    Elimination

    • Renal.
    • Mean plasma half-life: 21 hours after single or multiple doses.

    Topamax Interactions

    Interactions

    Contraindicated with metformin during metabolic acidosis condition. Concomitant other carbonic anhydrase inhibitors (eg, zonisamide, acetazolamide); monitor closely for acidosis. Antagonized by phenytoin, carbamazepine, valproic acid, lamotrigine; dose adjustment may be needed. Antagonizes valproic acid levels. May potentiate phenytoin levels, hydrochlorothiazide, amitriptyline, diltiazem. May antagonize digoxin, oral contraceptives, risperidone, pioglitazone (monitor glucose control). CNS depression potentiated with alcohol, other CNS depressants. Hyperammonemia (w/ or w/o encephalopathy) and/or hypothermia possible with valproic acid. Caution with other drugs that interfere with temperature regulation (eg, anticholinergics, carbonic anhydrase inhibitors). Monitor lithium levels with high-dose topiramate.

    Topamax Adverse Reactions

    Adverse Reactions

    Paresthesia, anorexia, weight decrease, taste perversion, upper RTI, abdominal pain, diarrhea, hypoesthesia, nausea, dizziness, nervousness, fatigue, somnolence, cognitive-related dysfunction (eg, confusion, psychomotor slowing, difficulty with memory, difficulty with concentration/attention, speech or language problems), psychiatric/behavioral disturbances (eg, depression, mood problems), fever, infection, flushing; serious skin reactions (eg, SJS, TEN), decrease in bone mineral density.

    Topamax Clinical Trials

    See Literature

    Topamax Note

    Not Applicable

    Topamax Patient Counseling

    See Literature

    Topamax Generic Name & Formulations

    Legal Class

    Rx

    General Description

    Topiramate 25mg, 50mg, 100mg, 200mg; tabs.

    Pharmacological Class

    Sulfamate.

    See Also

    How Supplied

    Tabs, Caps—60

    Manufacturer

    Janssen Pharmaceuticals, Inc.

    Generic Availability

    YES

    Mechanism of Action

    Topiramate blocks voltage-dependent sodium channels, augments the activity of the neurotransmitter gamma-aminobutyrate at some subtypes of the GABA-A receptor, antagonizes the AMPA/kainate subtype of the glutamate receptor, and inhibits the carbonic anhydrase enzyme, particularly isozymes II and IV.

    Topamax Indications

    Indications

    Initial monotherapy and adjunct in partial-onset or primary generalized tonic-clonic seizures. Adjunct in Lennox-Gastaut syndrome.

    Topamax Dosage and Administration

    Adult

    May swallow caps whole or sprinkle contents onto soft food (swallow immediately). Give in two equally divided doses. Monotherapy: initially 50mg/day, increase at 1-week intervals by increments of 50mg/week for the 1st 4 weeks, then increase by 100mg/week for Weeks 5–6 to target dose of 400mg/day. Adjunctive therapy: ≥17yrs: Initially 25–50mg/day, increase at 1-week intervals by 25–50mg/day every week (see full labeling) to target dose of 200–400mg/day (partial onset seizures or Lennox-Gastaut) or 400mg/day (primary generalized tonic-clonic seizures); usual max 1.6g/day. Renal impairment (CrCl <70mL/min): reduce dose by ½. Hemodialysis: may need extra dose.

    Children

    May swallow caps whole or sprinkle contents onto soft food (swallow immediately). Give in two equally divided doses. Monotherapy: <2yrs: not established. 2–<10yrs: (dosing based on weight) initially 25mg/day in the PM for the 1st week, then increase to 50mg/day in the 2nd week; subsequently, may increase weekly by 25–50mg/day as tolerated. Titration to the minimum or max maintenance dose should be attempted over 5–7 weeks: see full labeling. ≥10yrs: initially 50mg/day, increase at 1-week intervals by increments of 50mg/week for the 1st 4 weeks, then increase by 100mg/week for Weeks 5–6 to target dose of 400mg/day. Adjunctive therapy: <2yrs: not established. 2–16yrs: initially 1–3mg/kg (max 25mg) per day given in the PM for 1 week, increase at 1–2 week intervals by 1–3mg/kg/day to target range of 5–9mg/kg/day in 2 divided doses. Renal impairment (CrCl <70mL/min): reduce dose by ½. Hemodialysis: may need extra dose.

    Administration

    Do not break tablets (bitter taste).

    Nursing Considerations

    Do not break tablets (bitter taste). Counsel patients on effective birth control (potential decrease in efficacy with estrogen-containing birth control). Unexplained lethargy, vomiting, or changes in mental status may be symptoms of hyperammonemic encephalopathy. Watch for signs of decreased sweating and fever.

    Topamax Contraindications

    Not Applicable

    Topamax Boxed Warnings

    Not Applicable

    Topamax Warnings/Precautions

    Warnings/Precautions

    Discontinue if acute myopia and secondary angle-closure glaucoma syndrome occur. Consider discontinuing if visual field defects occur. Kidney stones. Maintain adequate hydration; avoid ketogenic diets. Measure serum bicarbonate at baseline, then periodically during therapy; consider reducing dose or discontinuing if metabolic acidosis develops and persists. Inborn errors of metabolism or reduced hepatic mitochondrial activity: increased risk of hyperammonemia; measure ammonia levels if encephalopathic symptoms occur. Monitor on growth (during prolonged therapy), oligohidrosis, and hyperthermia esp. in children. Suicidal tendencies (monitor). Discontinue at the 1st sign of a rash. Avoid abrupt cessation. Hepatic or renal impairment. Elderly. Fetal toxicity (eg, congenital malformations, oral clefts, small for gestational age). Labor & delivery. Pregnancy. Advise females of reproductive potential to use effective contraception during therapy. Nursing mothers.

    Topamax Pharmacokinetics

    Absorption

    • Peak plasma concentrations occurred at approximately 2 hours following a 400mg oral dose.

    Distribution

    • 15–41% plasma protein bound.

    Metabolism

    • Hepatic (minor). Metabolites are formed via hydroxylation, hydrolysis, and glucuronidation.

    Elimination

    • Renal.
    • Mean plasma half-life: 21 hours after single or multiple doses.

    Topamax Interactions

    Interactions

    Contraindicated with metformin during metabolic acidosis condition. Concomitant other carbonic anhydrase inhibitors (eg, zonisamide, acetazolamide); monitor closely for acidosis. Antagonized by phenytoin, carbamazepine, valproic acid, lamotrigine; dose adjustment may be needed. Antagonizes valproic acid levels. May potentiate phenytoin levels, hydrochlorothiazide, amitriptyline, diltiazem. May antagonize digoxin, oral contraceptives, risperidone, pioglitazone (monitor glucose control). CNS depression potentiated with alcohol, other CNS depressants. Hyperammonemia (w/ or w/o encephalopathy) and/or hypothermia possible with valproic acid. Caution with other drugs that interfere with temperature regulation (eg, anticholinergics, carbonic anhydrase inhibitors). Monitor lithium levels with high-dose topiramate.

    Topamax Adverse Reactions

    Adverse Reactions

    Paresthesia, anorexia, weight decrease, dizziness, nervousness, abnormal vision, fever, fatigue, somnolence, cognitive-related dysfunction (eg, confusion, psychomotor slowing, difficulty with memory, difficulty with concentration/attention, speech or language problems), psychiatric/behavioral disturbances (eg, depression, mood problems), infection, flushing, taste perversion; sudden unexplained death in epilepsy, serious skin reactions (eg, SJS, TEN), decrease in bone mineral density.

    Topamax Clinical Trials

    See Literature

    Topamax Note

    Not Applicable

    Topamax Patient Counseling

    See Literature

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