Key Takeaways

Topamax is an anticonvulsant medication used to manage seizures. One of the side effects is loss of appetite, so this medication is used off-label for weight loss in combination with an appetite suppressant called phentermine in addition to diet and exercise.
Topamax helps you lose weight through appetite suppression and by keeping you feeling full sooner. You will likely start on a low dose. There is no FDA-approved dosage.
Clinical trials show that using Topamax for weight loss can achieve about 5.34 kilograms (kg), which is about 11.7 pounds (lbs). You may start to notice some weight loss after about 4 weeks.

Topamax is an anticonvulsant medication that is used to manage seizures. Certain brands of Topamax are also used for migraine prevention.

Topamax is not specifically approved by the U.S. Food and Drug Administration as a weight loss drug but is used off-label for this purpose because of its effect of decreasing appetite.

Notably, when combined with another appetite suppressant called phentermine, Topamax is FDA-approved as a weight loss medication.

Please continue reading to find out more about the pros and cons of using Topamax to reduce body weight.

What is Topamax?

Topamax is a brand name product that contains the active ingredient topiramate, which is an anti-epileptic drug. This medicine is FDA-approved to treat seizure disorders and migraine prevention.

One of the side effects of Topamax is loss of appetite and weight loss. Clinical trials have shown that 6-17% of people who take this medicine lose weight. Topamax is, therefore, commonly used off-label for weight reduction, along with a reduced-calorie diet and exercise.

Who can take Topamax to lose weight?

A combination of two drugs, phentermine and topiramate, is available under the brand name Qsymia. Phentermine is an anorectic (appetite suppressant). Qsymia is used for chronic weight management, along with a reduced-calorie diet and increased physical activity.

This medicine is for people with a body mass index (BMI) of 30 kg/m2 (obese) and those with a BMI of 27 kg/m2 (overweight) with at least one weight-related health problem such as high blood pressure, high blood sugar levels, or high cholesterol.

Qsymia (phentermine and topiramate) is also approved for use in children aged 12 years and older whose BMI is at the 95th percentile or higher, standardized for age and gender.

How to take Topamax for weight loss?

Dosage and administration

Qsymia (phentermine and topiramate) comes in the form of extended-release capsules to be taken by mouth once a day in the morning. You can take the medicine with or without food.

Avoid taking the capsule in the evening, as phentermine is considered a stimulant, and it can cause sleep difficulties. Try to take your phentermine and topiramate at approximately the same time every day.

Regarding Topamax monotherapy, there is not an FDA-approved dose for weight loss. However, in studies, the dose range from 64 mg to 400 mg daily has been used and shows effectiveness in weight reduction. Unlike Qsymia, when used for weight loss, Topamax is taken twice daily in studies.

Read the prescription label carefully and follow the dosing instructions. Phentermine and topiramate can be habit-forming. Do not change the dose, dosing frequency, or treatment duration without talking to your health care professional.

Missed dose

If you miss a dose of your medicine, take it as soon as you remember. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not take extra medicine to make up for a forgotten dose.

Stopping treatment

Phentermine and topiramate help with weight loss only as long as you continue on the medicines.

Do not stop taking your weight loss medicine without talking to your doctor. Suddenly stopping this medicine can increase your risk of seizures. Your healthcare professional can tell you how to decrease the dose slowly.

How long does it take for Topamax to work for weight loss?

Topamax helps you lose weight through appetite suppression and by keeping you feeling full sooner. You may start to notice some weight loss on this medicine after about 4 weeks.

Your healthcare provider will likely start you on a starting dose of phentermine and topiramate combination (Qsymia 3.75 mg/23 mg) and increase the dose after 2 weeks.

They will evaluate your weight loss after 12 weeks of treatment. If you are not losing weight adequately, they may consider an additional dose increase.

Unlike Qsymia, Topamax monotherapy does not have an FDA-approved dosage for weight loss. Therefore, your doctor may increase the dose of Topamax at 1 to 2-week intervals based on your response to this medication while taking into consideration your overall health and other concurrent medications.

What is the average weight loss on Topamax?

Randomized controlled trials have shown that people who took topiramate lost an average of 5.34 kg (11.77 lbs) of additional weight compared to the placebo group.

The dosage and duration of treatment are closely linked to the effectiveness of topiramate in aiding weight loss. At doses ranging from 96 mg to 200 mg, weight loss was higher (6.58 kg) in trials that lasted more than 28 weeks compared to trials that lasted less than 28 weeks (4.11 kg).

Other clinical studies have shown that the average weight loss from baseline after 24 weeks on topiramate was 2.6% in the placebo group, 5.0% in people who took 64 mg of topiramate, 4.8% with a 96-mg dose, 6.3% with a 192-mg dose, and 6.3% with 384 mg/day of topiramate.

Generally speaking, you can expect to lose around 5-10% of your body weight with Topamax treatment, according to findings from clinical studies.

Will 25 mg of Topamax cause weight loss?

When Topamax is used off-label for weight loss, the initial dose is usually 25 mg to 50 mg once daily. If you tolerate the current dose, the Topamax dose is further increased over a period of several weeks based on your response.

While Topamax dosage ranges from 64 mg to 400 mg per day in studies, when being prescribed off-label for weight loss, prescribers usually don’t exceed 200 mg of Topamax daily. While higher doses may result in more weight loss, they are also associated with more undesirable side effects.

The dosing of Qsymia for weight loss is as follows: Starting dose of phentermine 3.75 mg and topiramate 23 mg once daily for 14 days. This is followed by a maintenance dose of phentermine 7.5 mg and topiramate 46 mg once daily for 12 weeks.

If adult patients have not lost at least 3% of their baseline weight or pediatric patients have not had a 3% reduction in baseline BMI, the dose of Qsymia may be increased to phentermine 11.25 mg and topiramate 69 mg once daily for 14 days. Following this, the dose can be increased to phentermine 15 mg and topiramate 92 mg once daily for 12 weeks.

If adult patients have not lost at least 5% of their baseline body weight or pediatric patients have not had a reduction of at least 5% from baseline BMI, then Qsymia is discontinued because it is unlikely to result in clinically meaningful and sustained weight loss.

What are the side effects of phentermine and topiramate?

Common adverse effects of phentermine and topiramate include dizziness, unusual sensations (numbness, tingling, burning) or decreased sensations in the skin, problems with memory, speech difficulties, changes in taste, stomach pain, nausea, diarrhea, dysmenorrhea (pain with menstrual periods), common colds symptoms (fever, sore throat, nasal congestion), fever, and weight loss.

Who should not take Qsymia for weight loss?

Tell your doctor if you have had an allergic reaction to topiramate (Topamax, Eprontia, Trokendi XR, Qudexy XR), phentermine (Lomaira, Adipex-P), or the following medications: phenylephrine, midodrine (Orvaten), aspirin, tartrazine (a yellow dye), other drugs used to control seizures, other CNS depressants (central nervous system depressants), or any of the active or inactive ingredients in Qsymia capsules.

Also, tell your doctor if you are taking or have taken within the last 2 weeks drugs called monoamine oxidase inhibitors (MAOI) (for example, isocarboxazid (Marplan), selegiline (Eldepryl, Emsam, Zelapar), phenelzine (Nardil), and tranylcypromine (Parnate).

Certain medicines can interact with topiramate and phentermine. Give your doctor and pharmacist a full list of your medications, including prescription drugs, over-the-counter medications, dietary supplements, vitamins, and herbal products. This can help avoid potentially dangerous drug interactions between Qsymia (phentermine and topiramate) and your other medicines.

Taking topiramate may not be right for people with certain health conditions. Tell your doctor if you have glaucoma, hyperthyroidism (overactive thyroid gland), heart attack or stroke in the past 6 months, suicidal thoughts or behavior, depression, mood changes, an eating disorder, a history of drug abuse, irregular heartbeat, heart failure, metabolic acidosis, low potassium, weak bones (osteoporosis, osteopenia), seizures, ongoing diarrhea, trouble breathing, kidney stones, diabetes, lung disease, kidney disease, liver disease, or if you are on a ketogenic diet (low carbohydrate, high-fat diet).

What precautions should I take while on Topamax for weight loss?

Pregnancy

Before starting treatment with Topamax or Qsymia, tell your doctor if you are pregnant or planning a pregnancy in the near future. The use of phentermine and topiramate during pregnancy can cause serious birth defects in the unborn baby, including cleft lip and cleft palate. This can happen very early in the pregnancy before you know you are pregnant.

You can only receive phentermine and topiramate from special pharmacies that participate in the Qsymia REMS (risk evaluation and mitigation strategy) program.

You must take birth control pills (oral contraceptives) or use some other method of contraception to prevent pregnancy during weight loss treatment with phentermine and topiramate.

Your healthcare provider will have you take a pregnancy test before starting treatment and once a month while you are on this drug combination. If you become pregnant while on phentermine and topiramate, stop the medicine and call your doctor without delay.

Driving and other hazardous activities

Phentermine and topiramate can affect your vision, cause dizziness, and slow your thinking and reaction time. Do not drive a car or operate machinery until you know how this weight loss drug affects you.

Keep in mind that alcohol is considered a CNS depressant, so it can worsen drowsiness and dizziness. You should avoid alcohol consumption while taking this medication.

Heat exposure

Qsymia can prevent your body temperature from cooling down through sweating. This can raise your risk of developing heat stroke in hot weather. Avoid unnecessary heat exposure, stay well hydrated, and call your doctor if you have ongoing diarrhea, upset stomach, headache, fever, or muscle cramps.

Mental health changes

Taking phentermine and topiramate can cause unexpected changes in your mental health, including suicidal thinking and behaviors. This can happen within a week of starting treatment.

Call your doctor immediately if you notice any unusual mood changes. Your family members or caregivers should know when and how to seek care if you are unable to do so yourself.

Watch out for symptoms such as panic attacks, restlessness, agitation, aggression, violence, anger, irritability, anxiety, depression, impulsiveness, sleep difficulties, abnormally excited mood, or suicidal thinking or behavior.

Slowed growth in children

Long-term use of phentermine and topiramate can slow height gain in children. If your child is taking these medications for weight loss, keep all healthcare appointments so that your child’s provider can keep an eye on their height.

How safe is Topamax for weight loss?

Some of the risks of taking Topamax or Qsymia (phentermine and topiramate) for weight loss are listed below. Seek immediate medical attention for these serious side effects:

Increased heart rate (palpitations or racing heart).
Suicidal behavior or thinking.
Eye problems (acute myopia and secondary angle-closure glaucoma).
Mood changes and sleep difficulties.
Cognitive impairment (difficulties with concentration, attention, memory, speech).
Metabolic acidosis (too much acid and low serum bicarbonate levels).
Fetal harm in pregnant women.
Slowed growth in children.
Decreased kidney function.
Hypoglycemia (low blood sugar) (this medicine combination can affect blood sugar levels in diabetic patients who are on a medication prescribed to control blood glucose levels).
Hypotension (low blood pressure) in people taking antihypertensive drugs.
Risk of seizures with sudden withdrawal of the medicine.
Kidney stones.
Decreased sweating.
Low potassium.
Allergic reactions (unusual or allergic reaction, including serious skin reactions and breathing problems, can occur after taking topiramate and phentermine).

Note: This medication guide is for information purposes only. It should not be used as a substitute for a professional medical consultation. Always seek treatment from a qualified healthcare professional for weight management.

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References:

https://medlineplus.gov/druginfo/meds/a612037.html
https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=21628112-0c47-11df-95b3-498d55d89593
https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=40dd5602-53da-45ac-bb4b-15789aba40f9#
https://pubmed.ncbi.nlm.nih.gov/21438989/
https://onlinelibrary.wiley.com/doi/10.1038/oby.2003.102
https://www.mayoclinic.org/drugs-supplements/phentermine-and-topiramate-oral-route/precautions/drg-20075700?p=1
https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=21628112-0c47-11df-95b3-498d55d89593

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