phentermine / topiramate
Qsymia (phentermine / topiramate extended release) is a combination medication used to help with weight loss. It's approved for people over 12 who are considered obese and for some adults who are considered overweight. This medication is a tablet that you take once a day. You should also eat a balanced diet and exercise regularly for best results. Side effects include a "pins-and-needles" feeling, dry mouth, and constipation. You can only get this medication through the Qsymia REMS (Risk Evaluation and Mitigation Strategies) program because of the risk of birth defects if taken during pregnancy.
What is Qsymia (phentermine / topiramate ER)?
What is Qsymia (phentermine / topiramate ER) used for?
Weight loss and long-term weight management, together with diet and exercise, for certain people:
People age 12 years and older considered obese
Adults considered overweight with at least one weight-related condition (e.g., heart disease, high blood pressure, Type 2 diabetes)
How Qsymia (phentermine / topiramate ER) works
Qsymia (phentermine / topiramate ER) is a combination of two active ingredients that work to help with weight loss.
Phentermine is a sympathomimetic. It works in the brain to lower your appetite.
Topiramate is an antiepileptic (anti-seizure medication). Scientists don't know exactly how it helps you lose weight. But it's thought to lower your appetite and also makes you feel more full.
Drug Facts
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What are the risks and warnings for Qsymia (phentermine / topiramate ER)?
Qsymia (phentermine / topiramate ER) can cause some serious health issues. This risk may be even higher for certain groups. If this worries you, talk to your doctor or pharmacist about other options.
Harm to an unborn baby
Risk factors: Currently pregnant | People who can become pregnant
Qsymia (phentermine / topiramate ER) can harm an unborn baby. So, you can't take this medication if you're pregnant. Studies show that taking topiramate, an ingredient in Qsymia, early in pregnancy can raise the risk of birth defects like cleft lip.
Because of this risk, the FDA put a special program called a Risk Evaluation and Mitigation Strategy (REMS) in place for the medication. Under the Qsymia REMS program, only certified pharmacies can fill your prescription for this medication.
If you can become pregnant, you'll need to follow specific directions to take Qsymia (phentermine / topiramate ER). Your prescriber will ask you to take a pregnancy test before starting the medication. You'll also need to take one every month during treatment. Use reliable birth control if you're having sex while taking this medication.
Mood problems and suicidal thoughts or behavior
Risk factors: History of depression | History of attempted suicide
Qsymia contains the anti-seizure medication, topiramate. Topiramate can raise the risk of suicidal thoughts or behavior, depression, and anxiety. In particular, the risk of suicidal thoughts can be higher as early as the first week of treatment. People with suicidal thoughts or who've tried to hurt themselves shouldn't take Qsymia (phentermine / topiramate ER).
Watch for signs of worsening depression or any unusual changes in your mood or behavior. This is especially important during the first few months of treatment or when your dose changes. Tell a healthcare professional if you or your loved ones notice anything troubling. Your prescriber might need to lower your dose of Qsymia (phentermine / topiramate ER) or stop treatment.
Call 911 right away if there are any suicidal thoughts or behaviors. Your prescriber will stop your Qsymia (phentermine / topiramate ER) treatment.
Fast heart beat
Qsymia (phentermine / topiramate ER) can make your heart beat faster. In studies, some people's heart rates went up by 5 beats per minute (bpm) or more, sometimes even up to 20 bpm. It isn't known yet how this might affect people with heart conditions in the long run. Let your prescriber know if you have any heart conditions before you start this medication. They can weigh the risks and benefits of treatment to make sure you stay safe.
Call your healthcare team if it feels like your heart is beating really hard or fast while you're resting (when you're sitting and haven't done any physical activity recently). They might want to check your heart and see if you should keep taking Qsymia (phentermine / topiramate ER).
Vision problems
Qsymia (phentermine / topiramate ER) can cause eye problems and vision changes. They can sometimes be serious and lead to blindness if not treated. If these eye problems happen, the symptoms usually show up during the first month after you start the medication. But they can also happen at any time during treatment. Call your prescriber right away if you have sudden changes in your vision, trouble seeing far away, or eye pain.
Problems concentrating
Risk factors: Raising the dose of Qsymia (phentermine / topiramate ER) too fast | Drinking alcohol | Taking other medications that can affect your concentration
Qsymia (phentermine / topiramate ER) can make it hard to concentrate. It can also cause problems with memory, speech, or language. This is more likely if you start treatment at a higher dose of Qsymia (phentermine / topiramate ER) or if your dose gets raised too quickly.
Try to avoid alcohol or limit how much you drink while taking Qsymia (phentermine / topiramate ER). This is because alcohol can make these problems worse. Don't drive or do anything that needs a lot of focus until you know how this medication affects you.
Tell your prescriber if you have trouble thinking or focusing. Also let them know if you feel dizzy, drowsy, or unsteady on your feet. Your prescriber might need to lower your dose of Qsymia (phentermine / topiramate ER) or stop your treatment altogether.
Higher level of acid in blood (metabolic acidosis)
Risk factors: Kidney problems | Severe breathing problems | Serious seizure situation called status epilepticus | Diarrhea | Keto diet | Taking medications called carbonic anhydrase inhibitors
Although rare, some people have had high acid levels in the blood while taking Qsymia (phentermine / topiramate ER). This condition is called metabolic acidosis. If not treated for a long time, it can lead to kidney problems or weak bones.
Your prescriber might have you get regular blood tests so they can check your blood acid levels. Tell your prescriber right away if you have fast and shallow breathing, feel nauseous, feel very tired, and have a fast heartbeat. These can be signs of metabolic acidosis.
Possible lower kidney function
Qsymia (phentermine / topiramate ER) can cause a rise in the creatinine levels in your blood. This can be a sign that your kidneys aren't working as well as they should. In studies, these lab changes usually showed up after a month or two of treatment.
To help keep you safe, your prescriber will check your kidney function before you start Qsymia (phentermine / topiramate ER) and during treatment. If your creatinine levels stay too high, your prescriber might lower your dose or stop treatment.
Kidney stones
Risk factors: Keto diet | Taking medications called carbonic anhydrase inhibitors
Qsymia (phentermine / topiramate ER) might cause kidney stones. The risk might be higher if you're on a ketogenic (keto) diet. You can also be at risk if you take medications called carbonic anhydrase inhibitors like acetazolamide. Be sure to drink plenty of fluids to prevent kidney stones from forming.
High body temperature and inability to sweat
Risk factors: Being outside at very hot temperatures | Taking medications called carbonic anhydrase inhibitors | Taking anticholinergic medications
Some people who take topiramate, one of the ingredients in Qsymia, have had a lower ability to sweat. This can make it harder to control your body temperature. Pay attention to how much you sweat or how hot you feel while you're exercising or in hot weather. Stay hydrated and take rest breaks in the shade on hot days.
Serious allergic reactions and skin reactions
Risk factors: Allergy to Yellow No. 5 dye
Qsymia (phentermine / topiramate ER) can cause severe allergic reactions and skin reactions. Call your prescriber if you notice a rash. And get medical help right away if you have trouble breathing, swelling of the face or lips, blisters on the skin, or fever.
Possible slowed growth in children
Studies show that Qsymia (phentermine / topiramate ER) might slow down growth in children 12 and older who are considered obese. In one study, children who took the medication for a year grew about 1 cm less than those who didn't take it.
Make sure your child goes to all their checkups so their prescriber can keep track of their growth. If your child isn't growing as expected, the prescriber might need to lower the dose of Qsymia (phentermine / topiramate ER).
What are the side effects of Qsymia (phentermine / topiramate ER)?
Common Side Effects
- Feeling of pins and needles (up to 20%)
- Dry mouth (up to 19%)
- Constipation (up to 16%)
- Upper respiratory tract infection (up to 16%)
- Headache (up to 11%)
- Change in taste (up to 9%)
- Trouble sleeping (up to 9%)
- Dizziness (up to 9%)
- Depression (up to 4%)
- Nausea (up to 4%)
- Fever (up to 4%)
- Dizziness (up to 4%)
- Joint pain (up to 4%)
Other Side Effects
- Nausea
- Diarrhea
- Back pain
- Tiredness
- Blurry vision
- Lower blood pressure
- Sinus infection
- Bronchitis
- Cough
- Urinary tract infection (UTI)
- Feeling of pins and needles
- Anxiety
- Stomach pain
- Muscle pain in the chest area
- Tiredness
- Ear infection
Serious Side Effects
- Suicidal thoughts or behaviors
- Vision problems: sudden changes in vision, sudden eye pain
- High acid levels in your body (metabolic acidosis): fast and shallow breathing, loss of appetite, tiredness, irregular heartbeat
- Severe skin reaction: rash, blisters, peeling skin, fever, body aches
- Serious allergic reaction: dizziness, flushing, trouble breathing, nausea, vomiting, fast heartbeat, rash, swelling in the face or tongue, trouble swallowing
- Seizure (after suddenly stopping the medication)
Source: DailyMed
More on Qsymia (phentermine / topiramate ER) side effects
The following side effects have also been reported
Side effects that you should report to your care team as soon as possible:
- Allergic reactions—skin rash, itching, hives, swelling of the face, lips, tongue, or throat
- Difficulty with paying attention, memory, or speech
- Fast or irregular heartbeat
- Fever that does not go away, decreased sweating
- High acid level—trouble breathing, unusual weakness or fatigue, confusion, headache, fast or irregular heartbeat, nausea, vomiting
- High ammonia level—unusual weakness or fatigue, confusion, loss of appetite, nausea, vomiting, seizures
- Kidney injury—decrease in the amount of urine, swelling of the ankles, hands, or feet
- Kidney stones—blood in the urine, pain or trouble passing urine, pain in the lower back or sides
- Low potassium level—muscle pain or cramps, unusual weakness or fatigue, fast or irregular heartbeat, constipation
- Mood and behavior changes—anxiety, nervousness, confusion, hallucinations, irritability, hostility, thoughts of suicide or self-harm, worsening mood, feelings of depression
- Redness, blistering, peeling, or loosening of the skin, including inside the mouth
- Sudden eye pain or change in vision such as blurry vision, seeing halos around lights, vision loss
Side effects that usually do not require medical attention (report to your care team if they continue or are bothersome):
- Burning or tingling sensation in hands or feet
- Change in taste
- Constipation
- Dizziness
- Dry mouth
- Trouble sleeping
Pros and cons of Qsymia (phentermine / topiramate ER)
Pros
A pill that's taken once a day
Combines two ingredients that help lower appetite into one pill for convenience
An option for certain children 12 years and older, if diet and exercise aren't enough
Cons
Can raise the risk of depression or thoughts of self-harm
Controlled substance and only available through a REMS program
Not safe during pregnancy
Pharmacist tips for Qsymia (phentermine / topiramate ER)
Take Qsymia (phentermine / topiramate ER) in the morning with or without food. Taking it earlier in the day can help prevent insomnia (trouble falling and staying asleep), which can be a side effect of the medication.
If you can have children, your prescriber might ask you to take a pregnancy test before starting Qsymia (phentermine / topiramate ER). You'll also need to take one every month during treatment. This medication can harm an unborn baby, so it's important to make sure you're not pregnant.
If you can have children, also talk to your prescriber about birth control methods to use while you're taking Qsymia (phentermine / topiramate ER). You might have more spotting (bleeding between periods) with some birth control pills.
You might notice or feel your heart beating faster than usual while taking Qsymia (phentermine / topiramate ER). It's not always dangerous, but it might be concerning. Let your prescriber know if you feel your heart pounding or racing.
Qsymia (phentermine / topiramate ER) can make you feel dizzy or confused. It can also cause changes in vision or make it hard to focus. Don't drive or do anything that needs your full attention until you know how this medication affects you.
Stay well hydrated during treatment. This can prevent kidney stones, which can form when you take medications that contain topiramate (like Qsymia). Tell your healthcare team know if you have severe back or side pain or any blood in your urine. These can be signs of a kidney stone.
It's best to avoid alcohol while taking Qsymia (phentermine / topiramate ER). Alcohol can make side effects like dizziness worse. It can also make it even harder for you to think clearly. And alcohol has extra calories that can contribute to weight gain. This isn't helpful if you're trying to lose weight. Talk to your prescriber if you drink alcohol often to see what's best for you.
Tell your prescriber if you take any medications that can lower your potassium, like furosemide (Lasix) or hydrochlorothiazide. Your potassium levels might drop even more if you take them with Qsymia (phentermine / topiramate ER). You might need blood tests to check your potassium levels regularly. Let your care team know if you have muscle cramps, constipation, weakness, dizziness, or trouble breathing. These can be signs of low potassium.
Don't stop taking Qsymia (phentermine / topiramate ER) without talking to your prescriber first, especially if you've been taking it for a long time. Stopping it too quickly can raise your risk of having a seizure. Your prescriber can help you stop the medication safely by lowering your dose slowly over time.
Breastfeeding isn't recommended while you're taking Qsymia (phentermine / topiramate ER). This medication can pass into your breast milk. It can raise the risk of side effects in your baby, like sleep problems, fussiness, high blood pressure, vomiting, and weight loss. Talk to your prescriber or a lactation consultant about your options.
Frequently asked questions about Qsymia (phentermine / topiramate ER)
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Qsymia (phentermine / topiramate ER) dosage forms
Typical dosing for Qsymia (phentermine / topiramate ER)
The typical starting dose is Qsymia 3.75 mg/23 mg (phentermine/topiramate) by mouth once a day in the morning for 2 weeks.
After that, your prescriber will raise your dose to the recommended dose of Qsymia 7.5 mg/46 mg (phentermine/topiramate) once a day.
Depending on how well the medication is working for you, your prescriber might adjust your dose. You must take Qsymia (phentermine / topiramate ER) along with eating a balanced diet and getting regular exercise.
The maximum dose is Qsymia 15 mg/92 mg (phentermine/topiramate) once a day. The maximum dose might be different if you have kidney or liver problems.
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Qsymia (phentermine / topiramate ER) contraindications
Currently pregnant
Hyperthyroidism (overactive thyroid condition)
Currently take or have taken medications called monoamine oxidase inhibitors (MAOIs) within the last 14 days
Allergy to phentermine or topiramate
What are alternatives to Qsymia (phentermine / topiramate ER)?
Weight loss and long-term weight management, together with diet and exercise, for certain people:
People age 12 years and older considered obese
Adults considered overweight with at least one weight-related condition (e.g., heart disease, high blood pressure, Type 2 diabetes)
Obesty management in adults with a body mass index (BMI) of:
Weight loss in adults when combined with a lower-calorie and low-fat diet
Long-term weight management in certain adults
What is the latest news about Qsymia (phentermine / topiramate ER)?
Qsymia (phentermine / topiramate ER) images
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References
Best studies we foundGadde, K. M., et al. (2011). Effects of low-dose, controlled-release, phentermine plus topiramate combination on weight and associated comorbidities in overweight and obese adults (CONQUER): A randomised, placebo-controlled, phase 3 trial. Lancet.
Gordon, B. (2023). What is the ketogenic diet? Academy of Nutrition and Dietetics.
Johnson, D. B., et al. (2023). Topiramate and phentermine. StatPearls.
Lonneman, D. J., Jr. (2013). Phentermine/topiramate extended-release capsules (Qsymia) for weight loss. Pharmacy and Therapeutics.
MedlinePlus. (2023). Metabolic acidosis.
National Heart, Lung, and Blood Institute. (n.d.). Assessing your weight and health risk.
National Institute of Diabetes and Digestive and Kidney Diseases. (2021). Overweight & obesity statistics.
National Kidney Foundation. (2024). Metabolic acidosis.
Qsymiarems.com. (n.d.). Risk evaluation and mitigation strategy (REMS).
U.S. Food and Drug Administration. (2022). FDA approves treatment for chronic weight management in pediatric patients aged 12 years and older.
Vivus LLC. (2024). Qsymia- phentermine and topiramate capsule, extended release [package insert]. DailyMed.
Vivus LLC. (2024). Risk of birth defects with Qsymia.
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