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Brands and Forms

  • Topamax
    • tablet: 25mg, 50mg, 100mg.
    • capsule, sprinkle: 15mg, 25m

Uses of Topiramate

In psychiatry, Topiramate can be used in the treatment of Bipolar Disorder, Binge-Eating Disorder, Bulimia Nervosa, Obsessive-Compulsive Disorder, and preventing or reversing weight gain caused by psychotropic medications.

In general medicine, Topiramate is used for treating seizure disorders and migraine headaches.

How Topiramate Works

Topiramate is an anticonvulsant and mood-stabilizer. It blocks voltage-gated sodium channels to alter signal transmission in neurons, inhibits the release of glutamate, potentiates the activity of GABA, and is a carbonic anhydrase inhibitor.

Cautions when Using Topiramate

Avoid excessive heat exposure, as Topiramate can cause reduced perspiration and hyperthermia.

Use caution in people at risk for narrow angle-closure glaucoma.

Topiramate can decrease the efficacy of oral contraceptives.

Dosing of Topiramate

For Bipolar Disorder and other psychiatric uses, the usual therapeutic range of Topiramate is 50-300mg/day (for epilepsy, the range is 200-400mg/day, and in rare cases up to 1600mg/day can be used). It is given twice daily.

It can be started at 25-50mg/day, and increased in increments of 50mg/day every week.

When wanting to stop this medication, it should be tapered over a period of a few weeks.

Onset of action

Therapeutic effects for psychiatric conditions are usually not expected before a few weeks.

Kidney impairment

Reduce dose by 50% if Ccr is less than 70ml/min. In cases of severe kidney impairment, recommended dose is 25mg/day.

Liver impairment

Use with caution.

Side-effects of Topiramate

Below is a list of most of the reported side-effects of Topiramate. Most of these side-effects occur in only a minority of individuals, and many also resolve with time while the medication is continued.

Cardiovascular: hypertension; bradycardia; fainting.

Central Nervous System: paresthesia; dizziness; fatigue; somnolence; psychomotor slowing; unsteadiness; confusion; difficulty with concentration; difficulty with memory; speech disorders; nystagmus; language problems; insomnia; tremor; abnormal gait; hypoaesthesia; hyperkinesia; abnormal coordination; involuntary muscle contraction; decreased libido; hypertonia; hyporeflexia; stupor; vertigo; migraine; convulsions; headache; sensory disturbance.

Dermatologic: hair loss; itchiness; rashes of various sorts; acne; increased sweating; bullous skin reactions.

Endocrine/Metabolic: weight decrease; thirst; hypoglycemia; metabolic acidosis (due to elevated bicarbonate levels), weight increase (rare).

Eyes, Ears, Nose and Throat: taste perversion; abnormal vision; double vision; pharyngitis; blurred vision; conjunctivitis; decreased hearing; otitis media; tinnitus; abnormal visual accommodation; abnormal lacrimation; eye pain; myopia.

Gastrointestinal: loss of appetite; nausea; diarrhea; abdominal pain; dyspepsia; increased saliva; constipation; dry mouth; gastritis; gastroenteritis; vomiting; gastroesophageal reflux; taste loss; dysphagia; fecal incontinence; flatulence; gingivitis; glossitis; gum hyperplasia; pancreatitis; hepatitis.

Genitourinary: breast pain; urinary incontinence; urinary tract infection; cystitis; menstrual disorder; premature ejaculation; kidney stones; vaginal hemorrhage; amenorrhea; dysuria; hematuria; leukorrhea; menorrhagia; urinary frequency; prostatic disorder; intermenstrual bleeding; nocturia; renal tubular acidosis.

Hematologic: easy bruising; nose bleeds; anemia; leukopenia; hematoma; increased bleeding time; thrombocytopenia.

Muskuloskeletal: joint pains; leg cramps; muscle pains.

Psychiatric: anxiety; depressed mood; apathy; agitation; irritability; emotional lability.

Respiratory: upper respiratory tract infection; sinusitis; bronchitis; rhinitis; pneumonia; coughing; shortness of breath; asthma; respiratory disorder.

Common side-effects of Topiramate

Paresthesia (sensations of prickling, tingling or numbness on one's skin), dizziness, fatigue, somnolence, feeling physically slowed, anxiety, depressed mood, unsteadiness, confusion, difficulty with concentration, difficulty with memory, speech problems, taste perversion, abnormal vision, double vision, loss or appetite, weight loss, nausea, diarrhea, upper respiratory tract infection.

Rare but serious side-effects of note of Topiramate

  • Metabolic acidosis due to elevated bicarbonate levels
  • Sudden unexplained death in epilepsy has been reported at an incidence of 0.0035 per patient-year.
  • Reduced sweating and hyperthermia has been reported mainly in children.

Topiramate overdose

Abdominal pain, abnormal coordination, agitation, blurred vision, depression, double vision, dizziness, drowsiness, hypotension, lethargy, confusion, severe metabolic acidosis, speech disturbance, stupor, convulsions. Can be fatal.

Topiramate and pregnancy

Category C: some animal studies show adverse effects at very high doses, but no controlled human studies have been done; should only be used in pregnancy if clearly needed and if benefits outweigh potential risks.

Medical Monitoring for Topiramate

Measure serum bicarbonate levels prior to starting the medication and then periodically while medication is being used (risk of elevated bicarbonate levels leading to metabolic acidosis).

Drug Interactions with Topiramate

  • Topiramate can increase blood concentrations of Amitriptyline, Metformin, Phenytoin
  • Topiramate can decrease blood concentrations of Digoxin, Lithium, Pioglitazone, Risperidone, and Valproic Acid.
  • Topiramate blood concentrations can be lowered by Carbamazepine, Metformin, Phenytoin, and Valproic Acid.
  • Topiramate blood concentrations can be increased by Hydrochlorothiazide, Lamotrigine,
  • Topiramate can decrease the efficacy of oral contraceptives.
  • Use caution when combining Topiramate with other carbonic anhydrase inhibitors (eg. Acetazolamide), as this increases the risk of renal stone formation.