Qsymia side effects — your complete guide

If you’re considering taking the oral weight loss medication Qsymia (phentermine/topiramate ER), you want to know about potential side effects. The most common Qsymia side effects include dry mouth, tingling, numbness, and constipation, but you might also experience symptoms like insomnia, taste changes, and dizziness, among others. 

In this guide, we cover all the possible Qsymia side effects and more, so you know exactly what to expect if you take it.

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What is Qsymia?

Qsymia (phentermine/topiramate ER) is a U.S. Food and Drug Administration (FDA)-approved oral weight loss medication that combines 2 medications, topiramate extended-release (ER) and phentermine, which work together to limit your food cravings and let you feel full longer. Phentermine is a popular short-term weight loss medication, while topiramate ER is a medication commonly used to treat migraines and epilepsy.

Unlike popular weight-loss injections like Saxenda, Wegovy, and Zepbound, Qsymia  kyoo-sim-EE-uh), is an oral capsule medication taken once a day in the morning. Like other weight loss medications, you need to combine Qsymia with exercise and diet and must have a qualifying body mass index (BMI) to take it.

Qsymia is approved by the FDA for adults with a BMI of 30 or higher, considered medically obese. It’s also approved for adults with a BMI of 27 or higher, as long as they also have at least 1 weight-related health issue, like heart problems, high cholesterol levels, type 2 diabetes, or high blood pressure. Qsymia is approved for children ages 12 or older in the obese range, which includes any BMIs in the 95th percentile or higher for their sex and age.

In Qsymia clinical trials, people taking it lost up to 10% of their initial body weight in 56 weeks. Some participants did have side effects. You may too if your provider prescribes it for you. Following is a breakdown of what you need to know.

Common side effects of Qsymia for weight loss

The most common Qsymia side effects experienced in clinical trials include the following.

• Numbness and tingling (paresthesia). You might experience some tingling or numbness in the face, feet, or hands if taking Qsymia. This side effect is typically more common with higher doses and may improve as your body gets used to the medication. 
• Dry mouth. Phentermine can reduce the amount of saliva your mouth makes, leading to dry mouth. Drink plenty of water throughout the day to combat a dry mouth. You can also try a saliva substitute, chew gum, or suck on hard candy to increase your saliva production.
• Constipation. You might get constipation when taking Qsymia, since phentermine can have a drying effect on your body. If you just have mild constipation, you can typically manage it by exercising regularly, drinking plenty of water, and increasing the amount of fiber you consume, in the form of whole grains, fruit, and vegetables.
• Upper respiratory tract infection. If you notice symptoms like a cough, fever, sore throat, or runny nose when taking Qsymia, you might have an upper respiratory tract infection. This side effect impacted about 16% of participants who were taking a low dose of Qsymia in a clinical trial.
• Headache. You might notice you have a headache from Qsymia, especially if you also have dizziness or insomnia. 
• Taste changes (dysgeusia). You might have a metallic taste in your mouth and other taste changes while taking Qsymia. These changes aren’t typically harmful, but impact quality of life for some people.
• Insomnia. Phentermine is a stimulant, and some people experience insomnia while taking Qsymia. Take it first thing in the morning to limit insomnia and avoid consuming caffeine. 
• Nasopharyngitis. You might experience nasopharyngitis when taking Qsymia. A fancy name for the common cold, nasopharyngitis is a throat and nose infection that causes symptoms like coughing, sneezing, and a runny nose.
• Dizziness. Much like tingling and numbness, dizziness is usually more common with higher doses of Qsymia and tends to improve as you adjust to it. Alcohol and other medications can worsen dizziness, so avoid drinking alcohol and check with your doctor before taking other medications at the same time as Qsymia.

Uncommon but milder side effects of Qsymia

There are uncommon but mild Qsymia side effects, including sinusitis, nausea, back pain, fatigue, diarrhea, bronchitis, urinary tract infections, cough, flu, joint pain, increased heart rate, and skin reactions.

Phentermine is a stimulant, so you might find that your heart rate increases while taking Qsymia. An increased heart rate can be scary, but as a Qsymia side effect, it’s typically not serious, and may or may not persist. That being said, it might not be the right medication for you if you have a history of heart issues.

Serious and rare side effects of Qsymia

Some of the more serious but rare Qsymia side effects include the following.

• Suicidal thoughts or actions. Suicidal thoughts and behaviors are another rare side effect of taking Qsymia. As an anti-seizure medication, topiramate is connected to an increased risk of suicidal thoughts. This side effect is most common within the first week of starting Qsymia, but can also happen at any time.
• Serious eye problems. In rare cases, taking Qsymia can lead to changes in vision. These vision changes tend to go away once you stop taking the medication, but occasionally, are connected to increased pressure in your eye, which tends to happen within the first month. Symptoms of increased eye pressure include sudden blurred vision or eye pain.
• Concentration, memory, or speech difficulties. You might have issues with focusing, thinking clearly, finding the right words, or remembering things while taking Qsymia. These attention and memory issues tend to be more common with higher doses or if you take Qsymia with alcohol, some anxiety medications, or other medications with sedative effects.
• Decrease in kidney function. Qsymia can lead to an increase in serum creatinine, which causes a decrease in kidney function. 
• Possible seizures. If you end up stopping Qsymia abruptly, you might experience seizures, especially if you have a history of epilepsy or seizures. If you need to stop taking Qsymia immediately, you should be monitored for seizures.

Drugs that can interact with Qsymia

Different drug interactions can happen when taking Qsymia.

• Birth control pills. Qsymia might affect the levels of birth control hormones in your body, which shouldn’t impact the effectiveness of your pills but might lead to breakthrough spotting or bleeding. 
• Alcohol. Mixing Qsymia with alcohol can increase the chance of side effects like drowsiness, dizziness, and difficulty with focus, so you should reduce your alcohol consumption or stop drinking while on Qsymia.
• Central nervous system (CNS) depressants. CNS depressants are any medications that slow down the activity in your brain, including opioids, barbiturates, and benzodiazepines. Taking these drugs with Qsymia can lead to dizziness and drowsiness.
• Other weight loss medications. Qsymia contains both phentermine and topiramate, and experts don’t recommend taking more than 1 weight loss medication with the same ingredient, since it could increase your side effects and damage your health.
• Some non-potassium sparing diuretics. Also known as water pills, some diuretics can lower your potassium. Since Qsymia can also potentially reduce your levels of potassium, taking a diuretic and Qsymia at the same time can lead to hypokalemia, meaning that your potassium drops too low. Hypokalemia can cause muscle cramps, weakness, and issues with your heartbeat.
• Some anti-seizure medications. The antiepileptic drugs phenytoin and carbamazepine can lower the levels of Qsymia in people with epilepsy, making it less effective. 
• Carbonic anhydrase inhibitors. When combined with Qsymia, valproic acid can increase your blood ammonia levels or lead to a dangerous drop in body temperature.
• Pioglitazone. A medication for diabetes, pioglitazone interacts with the topiramate found in Qsymia. When you take both medications at the same time, there’s a decrease in the exposure and effectiveness of pioglitazone.
• Amitriptyline. When you take both Qsymia and amitriptyline at the same time, there’s a large boost in the concentration of amitriptyline because of the topiramate found in Qsymia.
• Monoamine oxidase inhibitors (MAOIs). Used to treat Parkinson’s disease and depression, MAOIs can interact with Qsymia by increasing the risk for a hypertensive crisis, meaning that your blood pressure gets dangerously high.

Warnings for Qsymia

Speak to your doctor or pharmacist or read the Qsymia medication guide for a full list of side effects, including drug interactions, contraindications, serious side effects, and side effects for children. Since Qsymia includes phentermine, which is a Schedule IV controlled substance, Qsymia may cause abuse or dependence.

Here are some other warnings to keep in mind when taking Qsymia.

• Mood and sleep disorders. Qsymia can lead to insomnia and mood disorders like anxiety and depression. If you already have a history of depression, make sure your provider knows and use caution, because there’s an increased risk of depression and other mood disorders while taking Qsymia.
• Cognitive impairment. Qsymia can lead to cognitive dysfunction, including trouble finding the right words, problems with speech or language, trouble remembering things, and difficulty with attention or concentration.
• Metabolic acidosis. Qsymia can cause metabolic acidosis, which means that acids build up in your body, leading to an abnormally low serum bicarbonate level. Metabolic acidosis can cause symptoms like hyperventilation, anorexia, fatigue, or cardiac arrhythmias.
• Kidney stones. Qsymia is often connected with the formation of kidney stones, since the topiramate found in Qsymia limits carbonic anhydrase activity, reduces urinary citrate excretion, and increases urine pH. If you’re on a ketogenic diet, you’re at a higher risk for kidney stones. 
• Oligohidrosis and hyperthermia. The use of topiramate, found in Qsymia, has been associated with oligohidrosis or decreased sweating, which can lead to hospitalization. Decreased sweating can also cause hyperthermia or an increase in your body temperature beyond what’s normal.
• Hypokalemia. Qsymia can increase the risk of hypokalemia, or low potassium, due to it limiting carbonic anhydrase activity. Your provider will want to measure your potassium levels both before and during your Qsymia use to ensure your levels don’t get too low.
• Serious skin reactions. Some patients report serious skin reactions when taking topiramate, which is found in Qsymia. If you notice a skin reaction or rash while taking Qsymia, stop taking it immediately, unless you’re sure the skin reaction isn’t related to the drug.
• Allergic reactions due to inactive ingredient FD&C Yellow No. 5. Qsymia contains the inactive ingredient FD&C Yellow No. 5, also known as tartrazine, which can cause allergic reactions like bronchial asthma in some patients. 

Who shouldn’t take Qsymia?

You shouldn’t take Qsymia if you:

• Have thyroid problems or glaucoma
• Are pregnant, planning to become pregnant, or become pregnant while taking Qsymia
• Are allergic to sympathomimetic amines like phentermine, topiramate, or any Qsymia ingredients
• Currently take an MAOI or have taken them within the past 14 days

If you’re pregnant, planning to become pregnant, or become pregnant while taking Qsymia, stop taking it immediately and talk to your healthcare provider. Qsymia can cause fetal harm and birth defects, including congenital malformations, oral clefts, and low birth weight. Weight loss also offers no clinical benefit if you’re pregnant and may be harmful to you or your baby.

How to minimize Qsymia side effects

The best way to minimize the potential side effects of Qsymia is to start the medication at a low dose and work with your provider to gradually increase your dose to the best maintenance dose for you. Gradually increasing your dose lets your body get used to Qsymia and minimizes the risk of side effects. 

Your provider will likely have you start with the smallest available dose of Qsymia, which is a 3.75 mg/23 mg capsule, and stay at that dose for 14 days. After that, they may have you increase to the 7.5 mg/46 mg dose. Higher doses are available and can be used if after 3 months you haven’t lost at least 3% of your body weight.  

Make sure to let your healthcare provider know if you do get side effects at any time while taking Qsymia so they can adjust your medication if needed. 

You can also consider reporting any negative side effects to the FDA by visiting MedWatch or calling 1-800-FDA-1088.

How to manage the side effects of Qsymia

To help manage side effects like dry mouth and constipation and reduce your risk of getting kidney stones while on Qsymia, drink plenty of water and other fluids. And contact your provider immediately if you have annoying side effects or uncommon or serious side effects like increased heart rate, vision changes, and suicidal thoughts or behaviors.

What to do if you miss a dose of Qsymia

If you miss a dose of Qsymia, take the medication as soon as you can. If it’s almost time to take your next dose of Qsymia, simply skip taking the missed dose and take the next dose as planned. Never take a double dose of Qsymia, since this could increase your risk for side effects.

And if you overdose, consider contacting the Poison Help line at 1-800-222-1222, your provider, or call 9-1-1.

Key takeaways

• Qsymia is an FDA-approved oral weight loss medication that combines 2 medications, topiramate extended-release (ER) and phentermine, which work together to limit your food cravings and enable you to feel full longer so you lose weight.
• The most common Qsymia side effects experienced in clinical trials include tingling (paresthesia), dry mouth, constipation, upper respiratory tract infection, headache, taste changes (dysgeusia), insomnia, nasopharyngitis, and dizziness.
• Qsymia can have drug interactions, including birth control pills, alcohol, central nervous system (CNS) depressants, other weight loss medications, some diuretics, some anti-seizure medications, carbonic anhydrase inhibitors, pioglitazone, amitriptyline, and monoamine oxidase inhibitors (MAOIs). 
• Speak to your healthcare provider or pharmacist or read the Qsymia medication guide for a full list of side effects, including drug interactions, contraindications, serious side effects.

See if Qsymia is right for you

If you’re interested in taking weight loss medication, Qsymia might be the right medication for you. Speak to a provider on Klarity today to look into Qsymia and discover if it’s a medically necessary part of a weight loss treatment plan for you.

FAQs about Qsymia side effects

Does Qsymia have long-term side effects?

When used over the long term, Qsymia might slow the growth of children aged 12 years and up, affecting their height. Qsymia can also cause long-term vision changes, particularly if you don’t address vision changes that come up right away. 

Will the side effects of Qsymia go away?

Most side effects associated with Qsymia will go away, either when you stop taking the medication or as your body adjusts to taking it.