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How long does it take for Topamax to start working?

Medically reviewed by Leigh Ann Anderson, PharmD. Last updated on June 18, 2025.

Official Answer by Drugs.com

Your doctor will prescribe a lower dose of Topamax at the beginning. Your dose will be slowly increased to the amount needed to control your seizures or migraine and to help limit side effects.

Your dose is not usually increased more than once per week. Your dose will be gradually increased until you have an effective response, reach a maximum allowed dose, or have intolerable side effects.

Related: Topamax dosage (in more detail)

Take Topamax every day as directed by your doctor. Do not change your dose without speaking to your doctor first. Before stopping, it is recommended that the dose be reduced gradually.

When taken twice a day, the medicine is usually taken in the morning and evening. At the beginning of treatment for some uses, your dose may be taken only at night for a short while.

Why is Topamax prescribed?

Topamax (topiramate), classified as an anticonvulsant medicine, is an oral medication taken alone or with other medicines to control certain types of seizures due to epilepsy and for the prevention of migraine headaches.

It is approved by the FDA:

Topamax may cause drowsiness, dizziness, blurred vision or impair your thinking and reaction time. Avoid driving or operating machinery until you know how this medicine will affect you.

You can take Topamax with or without food. The tablets are bitter so do not break, crush or split them. Do not drink alcohol while taking Topamax as it may worsen side effects like drowsiness or dizziness. Drink plenty of fluids during the day to help prevent kidney stones.

Learn more: View Topamax side effects, warnings and drug interactions (in more detail)

This is not all the information you need to know about Topamax (topiramate) for safe and effective use and does not take the place of talking to your doctor about your treatment. Review the full patient information for Topamax and discuss this information and any questions you have with your doctor or other health care provider.

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How long does Topamax stay in your system?

Topamax stays in your system for approximately 4 to 5 days after the last dose, but this may vary depending on personal factors, such as your age, weight, dosage, and what other medications you currently take. This estimate is based on the half-life of Topamax which is about 21 hours and experts agree that it takes up to 5 half-lives for a drug without active metabolites to be completely removed from the body. A drug’s half-life is the time it takes for 50% of that drug to be removed from the body. Topamax does have some metabolites, but these are not considered active and only make up about 5% of an administered dose. This means it takes 84 to 105 hours for Topamax to leave your body. Continue reading

How does Trokendi XR help with weight loss?

Trokendi (topiramate) XR can lead to weight loss when used for prevention of migraine headaches or seizures, but it is not approved as a weight loss medicine. Loss of appetite and other digestive issues, which may contribute to weight loss, have been reported in topiramate studies. Continue reading

Are Topamax and Trokendi XR the same thing?

Topamax and Trokendi XR and are both approved by the FDA for seizure control in certain forms of epilepsy and for migraine headache prevention, but there are differences between these drugs, including approved ages for use, dosage forms, and dosing schedules. Continue reading

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