How Does Topirmate for Weight Loss Work?


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Topiramate, also sold under the brand name Topamax, is a drug approved by the U.S. Food and Drug Administration (FDA) for epilepsy and migraines. It’s also prescribed off-label for weight loss. But the combination of topiramate and phentermine, sold under the brand name Qsymia, is FDA-approved for weight management. 

Studies show topiramate causes a significant reduction in body weight. It’s unclear how exactly topiramate weight loss works, but we know that this medication can suppress your appetite and help you feel fuller for longer. 

Got questions? We’ve got answers. Keep reading to learn how topiramate works for weight loss, how long it takes to work and the side effects you should know about. 

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What Is Topiramate?

Topiramate is an antiepileptic agent. As the name suggests, it’s FDA-approved for epilepsy, as well as to prevent migraines. It’s also used as an adjunctive therapy — meaning it’s used with another, primary treatment — for those with mood disorders, eating disorders or alcohol use disorders. 

One of the side effects of this medication is weight loss, so topiramate is sometimes prescribed off-label to help people lose weight. For weight loss, topiramate is best used alongside diet and exercise changes. 

It’s also found in the drug Qsymia, which contains extended-release topiramate and phentermine and is FDA-approved for weight management. Qsymia is prescribed alongside a reduced-calorie diet and increased physical activity for those with a body mass index (BMI) of 30 or greater or a BMI of 27 or greater with at least one weight-related comorbidity — like high blood pressure, diabetes or high cholesterol. 

Studies on topiramate for weight loss are pretty positive. 

In a 2012 study, for example, 385 participants with obesity followed a lifestyle program and took either a placebo or topiramate for 24 weeks. Those on topiramate started on a daily dose of 16mg and gradually moved up to a daily dose of either 64mg, 96mg, 192mg or 384mg. 

At the end of the study, the placebo group had a mean weight loss of 2.6 percent. Those on topiramate lost more weight. And, for the most part, the higher the dose, the more weight they lost. 

Here’s what the results showed: 

  • Those taking 64mg had a mean weight loss of 5 percent 

  • Those taking 96mg had a mean weight loss of 4.8 percent

  • Those taking 192mg lost had a mean weight loss of 6.3 percent

  • Those taking 384mg lost had a mean weight loss of 6.3 percent 

While participants did experience side effects, most of these happened early in treatment, were dose-related and resolved by themselves. 

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How Does Topiramate for Weight Loss Work?

So, we know topiramate can cause significant weight loss, but how exactly does this effect happen? Well, it’s not entirely clear. 

It’s believed that topiramate can reduce your calorie intake, decrease fat gain and lower triglyceride and cholesterol levels. It may do this by: 

  • Suppressing appetite

  • Causing you to feel full for longer after you eat

  • Reducing leptin, a hormone correlated with weight reduction 

  • Altering reward pathways to reduce binge eating 

  • Stimulating the enzyme lipoprotein lipase and increasing thermogenesis (the production of heat) and substrate oxidation (the breakdown of nutrients), both of which can lead to weight loss

In Qsymia, phentermine may suppress appetite and increase metabolism, too.

In simple terms, you may feel less hungry and more full, leading you to consume fewer calories, curb hunger and lose weight. But there may be other mechanisms at play. 

As well as aiding weight loss, topiramate can help those with type 2 diabetes improve their glycemic control, or better manage their blood sugar levels. 

2013 study looked at 69 participants who took either topiramate or a placebo for 32 weeks while following the same lifestyle changes. Those taking topiramate saw a more significant reduction in BMI, more weight loss and lower systolic blood pressure and HgA1c (a measure of blood sugar levels) than those taking the placebo. 

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What’s the Best Topiramate Dosage for Weight Loss?

There isn’t one best topiramate dosage for weight loss — because the drug is prescribed off-label for weight loss, there haven’t been official clinical trials on this topic. 

Studies suggest that higher doses, such as 192mg and 384mg, are more effective than lower doses, such as 64mg and 96mg. But higher doses also come with a higher risk of side effects. 

Your healthcare provider may start you on a low dose of topiramate and slowly increase it over several weeks. The maximum dose of Topamax for weight loss will be different for everyone. 

Daily doses for topiramate weight loss are lower than they would be for epilepsy or migraines. 

But we know the best dosages for Qsymia, the phentermine-topiramate combo. If you take Qsymia, the starting dose is 3.75mg of phentermine and 23mg of topiramate daily for 14 days. The dose then increases to 7.5mg of phentermine and 46mg of topiramate daily for 90 days. 

If you need a higher dose after 90 days, your provider can prescribe up to 11.25mg of phentermine and 69mg of topiramate daily for 14 days, followed by 15mg of phentermine and 92mg of topiramate daily from there. 

Phew, that’s a lot of numbers. But don’t worry, your provider will tell you your ideal Topamax or Qsymia dosage for weight loss, including your starting dose and when to increase it.

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How to Take Topiramate for Weight Loss?

Take topiramate as directed by your provider and the prescribing label. 

There aren’t clear guidelines for the best time to take Topamax for weight loss, but you can ask your provider if they have any recommendations for when you should take topiramate. 

If not, pick the time that suits you and will reduce the likelihood of forgetting a dose — for example, first thing in the morning, before you make breakfast. 

And speaking of breakfast, you can take Topamax with or without food. 

Topiramate is available in tablet form in 25mg, 50mg, 100mg and 200mg doses, and in sprinkle capsules in 15mg and 25mg doses. 

Sprinkle capsules can be swallowed whole — like a regular tablet — or opened and sprinkled (hence the name) onto a small amount of soft food and swallowed immediately, for those who have trouble swallowing tablets.

If you’re taking Qsymia, consider taking it in the morning, as it can cause trouble sleeping if taken in the evening. You should take Qsymia at the same time each day, and — just like topiramate — you can take it with or without food. 

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How Long Will It Take Topiramate to Work?

There’s no set time frame for topiramate to start working for weight loss, as it’s not designed to be a weight loss medication. Research shows some people begin to experience weight changes in their second week on the drug and continue losing weight the longer they take it. 

But weight loss is highly individual, so this may vary from person to person. You may also see results more quickly if you combine topiramate with other healthy habits, like regular exercise and a healthy, reduced-calorie diet full of fruits and vegetables, whole grains and lean meats.

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Topiramate Side Effects

Common side effects of topiramate include: 

  • Weight loss — you probably knew this one

  • Paresthesia (skin tingling or numbness) 

  • Fatigue 

  • Dizziness 

  • Somnolence (drowsiness) 

  • Nervousness 

  • Psychomotor slowing (such as slowed thinking and movements) 

  • Memory problems 

  • Trouble concentrating or paying attention 

  • Cognitive problems 

  • Confusion 

  • Mood problems 

  • Anorexia 

  • Flushing 

  • Fever

  • Infection 

There are also some more serious side effects to watch out for. For example, antiepileptic drugs, including topiramate, can increase the risk of suicidal thoughts and behavior. Look out for unusual mood or behavior changes, worsening depression or thoughts about self-harm, and seek medical help immediately if you notice any changes. 

Adverse effects can also occur with Qsymia. Contact your healthcare provider if you have any concerns about side effects.

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What Should I Avoid While Taking Topiramate?

You should avoid drinking alcohol while taking topiramate. The combination can cause sleepiness and dizziness. 

Depending on how you’re feeling, you might want to avoid driving and operating machinery. 

Certain side effects of topiramate —  like psychomotor slowing, confusion, trouble concentrating and dizziness — can make these activities more dangerous. 

If you’re feeling any of these effects, consider avoiding situations where this could put you or others in danger —  AKA leave the car at home and call an Uber. 

Image Credit: Viktoria Korobova/Istockphoto.

Who Should Not Take Topiramate?

There are a few groups of people who shouldn’t take topiramate, while others may need a different dose than usual.

Let your healthcare provider know if you:

  • Are pregnant or trying to get pregnant, or if you become pregnant while on topiramate 

  • Are breastfeeding

  • Take any prescription drugs or over-the-counter vitamins or supplements 

  • Have kidney problems, including kidney stones

  • Have liver problems 

  • Have osteoporosis (weak or brittle bones) 

  • Have eye problems like glaucoma

  • Have depression or mood problems 

  • Have a history of metabolic acidosis (too much acid in the blood) 

  • Have lung or breathing problems 

  • Have diarrhea 

  • Have a growth problem  

  • Are on a ketogenic diet (high-fat, low-carb) 

If you take it during pregnancy, topiramate can cause your baby to develop a cleft lip or cleft palate. A healthcare professional can help you weigh whether the benefits of taking topiramate outweigh the risks in this case.

You shouldn’t take topiramate if you’re taking a carbonic anhydrase inhibitor — a class of medications used to treat conditions like glaucoma, altitude sickness and congestive heart failure. 

You should also avoid topiramate if you’re on any medications that can cause metabolic acidosis. In addition, topiramate itself can cause metabolic acidosis, and this affects what other drugs you can take. Metformin — the diabetes drug sometimes used for weight reduction — shouldn’t be used in those with metabolic acidosis, for example. 

Hypothermia and hyperammonemia — when your levels of ammonia are too high — have also been reported in those taking topiramate and valproic acid, a drug for certain types of seizures, mania and bipolar disorder. 

A healthcare professional may prescribe a different dose than usual if you’re undergoing hemodialysis or have kidney impairment, especially if you’re 65 or older. 

Word of warning: Topiramate may decrease the effectiveness of birth control pills. It can also increase breakthrough bleeding or spotting, especially at doses greater than 200mg a day. Talk to your healthcare provider about whether you need a different form of contraception while taking topiramate. 

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Topamax Weight Loss: Is It For You?

Topamax and weight loss could be a match made in heaven, but it’s not for everyone. And it’s not designed as a quick fix. The drug may be prescribed alongside diet and exercise changes to help you reach your weight loss goals.

Here are the key facts: 

  • Topiramate could help you lose weight. Research shows it can promote weight loss, reduce BMI and improve blood sugar control. It can act as an appetite suppressant and help you feel fuller for longer, although it’s not exactly clear how.

  • It’s not FDA-approved for weight loss. Topiramate weight loss is shown in studies, but it’s not approved as a weight loss drug on its own. It’s designed as an anticonvulsant for epilepsy and migraine prevention and prescribed off-label for weight loss. Qsymia, which contains topiramate, is FDA-approved for weight loss. 

  • Topiramate side effects exist. And they go beyond weight loss. Look out for fatigue, dizziness and mood changes, and contact a healthcare professional if you notice anything off. 

Speak to a healthcare provider to determine if topiramate is right for you. 

If not, or if you’re still exploring your options, don’t worry. Topiramate isn’t the only way to lose weight. In addition to lifestyle changes, there are other weight loss pills, weight loss injections and drug-free interventions available. You can learn more about the weight loss treatments out there.

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