Topamax: 7 things you should know
Medically reviewed by Carmen Pope, BPharm. Last updated on July 25, 2023.
1. How it works
- Topamax is a brand (trade) name of topiramate. Topamax reduces the frequency and duration of seizures and is used in the treatment of certain types of epilepsy. It also prevents the development of migraine headaches.
- Experts aren't sure exactly how topiramate works in either epilepsy or to prevent migraines but research suggests it dampens down excessive nerve firing, enhances the actions of GABA, and blocks the effects of other chemical messengers.
- Topamax belongs to the class of medicines known as carbonic anhydrase inhibitors or carbonic anhydrase inhibitor anticonvulsants. It may also be called an anticonvulsant.
- May be used by itself or in addition to other medications for the treatment of partial-onset or primary generalized tonic-clonic seizures in adults and children over the age of two.
- May be used in addition to other medications for the treatment of Lennox-Gastaut syndrome in adults and children over the age of two.
- May also be used for the prevention of migraine in adults and children over the age of 12. Topamax will not stop a migraine once it has started.
- Does not require monitoring of blood concentrations.
- May be taken with or without food.
- Available in four different strengths: 25mg, 50mg, 100mg, or 200mg.
- Topamax is available as a generic under the name topiramate. Sprinkle capsules contain small, white to off-white spheres and are available as 15mg and 25mg.
If you are between the ages of 18 and 60, take no other medication or have no other medical conditions, side effects you are more likely to experience include:
- Drowsiness that may affect your ability to drive or operate machinery. Alcohol should be avoided.
- Sudden eye pain and decreased vision associated with or without glaucoma have been reported; symptoms may occur in both children and adults and typically start within 1 month of starting therapy. Urgent medical attention should be sought. Drug discontinuation may be necessary to avoid permanent vision loss.
- Reduced ability to sweat and increased body temperature. This is more likely to occur in children, especially in hot weather or when used in conjunction with other drugs that also raise body temperature (such as acetazolamide or hyoscine). Hypothermia (low body temperature) has also been reported when Topamax is taken in conjunction with valproate.
- Confusion, difficulty with concentration/attention, forgetfulness, speech or language difficulties, depression or mood problems, flushing, fever, tiredness, fatigue, weight decrease, or tingling of the extremities are common side effects. Visual field disturbances have been reported following Topamax use. Most cases were reversible when the drug was stopped.
- The risk of kidney stones in people taking Topamax is two to four times higher than in the general population.
- May cause disturbances in bicarbonate levels leading to metabolic acidosis. The risk is greater when Topamax is coadministered with metformin.
- Rarely, Topamax has been associated with sudden unexplained death.
- The dosage needs to be gradually increased over at least six weeks.
- Topamax will not treat a migraine, it will only help prevent one from developing.
- As with other antiepileptics, Topamax may increase the risk of suicidal thoughts or behavior; monitor for worsening depression or mood changes.
- The dosage of Topamax may need to be reduced in people with kidney or liver disease. In people with CLCR of less than 70mL/min/1.73m2, one-half of the usual dosage is recommended. In people undergoing hemodialysis, a supplemental dose of Topamax may be required.
- May interact with several other drugs including seizure medications (such as phenytoin or carbamazepine), oral contraceptives, lithium, and pioglitazone.
- Reliable contraception should be used if Topamax is taken by women of childbearing age as the use of Topamax has been associated with cleft lip or palate in the developing baby.
Note: In general, seniors or children, people with certain medical conditions (such as liver or kidney problems, heart disease, diabetes, seizures) or people who take other medications are more at risk of developing a wider range of side effects. View complete list of side effects
4. Bottom Line
Topamax may be prescribed either alone or in combination with other medications for the treatment of certain types of epilepsy, or it may be given for the prevention of migraine. Drowsiness is a common side effect and it may occasionally cause visual or metabolic disturbances.
- Can be taken with or without food.
- Either swallow Topamax Sprinkle Capsules whole or carefully open and sprinkle the entire contents on a small amount (teaspoon) of soft food. Swallow the drug/food mixture immediately without chewing. Do not store for future use.
- Tablets have a bitter taste; do not break.
- Topamax is usually started at a low dosage and then titrated up slowly until an effective dose is reached (experts suggest increasing by 25 mg/day every week). Your doctor will explain this to you.
- Topamax should be discontinued slowly to minimize the potential for seizures unless a rapid withdrawal is justified.
- Do not drive or operate machinery or perform other hazardous tasks if Topamax makes you dizzy or drowsy. Alcohol can potentiate these effects so should be avoided.
- Seek urgent medical attention if you develop eye pain, blurred vision, or visual disturbances while taking Topamax.
- Also, report any changes in mood or the development of depression or suicidal thoughts to your doctor.
- Keep up your fluid intake and avoid dehydration as Topamax can increase the risk of kidney stones developing. Topamax may also make you sweat less or give you a fever. Contact your doctor if your fever does not go away, you develop abdominal pain with or without vomiting, or you are unable to sweat.
- Topamax should not be taken during pregnancy or while breastfeeding. If you inadvertently become pregnant while taking Topamax, talk with your doctor straight away.
6. Response and effectiveness
- Peak concentrations of Topamax are reached within two hours of oral administration. Some effects are apparent within a few days of taking Topamax; however, it may take up to eight weeks before the full effects are seen.
Medicines that interact with Topamax may either decrease its effect, affect how long it works, increase side effects, or have less of an effect when taken with Topamax. An interaction between two medications does not always mean that you must stop taking one of the medications; however, sometimes it does. Speak to your doctor about how drug interactions should be managed.
Common medications that may interact with Topamax include:
- antidepressants, such as monoamine oxidase inhibitors (eg, isocarboxazid, selegiline, or tranylcypromine)
- antiepileptics, such as carbamazepine, phenytoin, and valproate
- diuretics, such as HCTZ
- oral contraceptives
Alcohol may enhance the sedative effects of Topamax.
Note that this list is not all-inclusive and includes only common medications that may interact with Topamax. You should refer to the prescribing information for Topamax for a complete list of interactions.
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Related treatment guides
- Topamax (topiramate) [Package Insert]. Revised: 05/2023. Janssen Pharmaceuticals, Inc. https://www.drugs.com/pro/topamax.html
Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use Topamax only for the indication prescribed.
Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.
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