Qsymia Side Effects

Generic name: phentermine / topiramate

Medically reviewed by Drugs.com. Last updated on Jun 23, 2023.

Note: This document provides detailed information about Qsymia Side Effects associated with phentermine / topiramate. Some dosage forms listed on this page may not apply specifically to the brand name Qsymia.

Applies to phentermine / topiramate: oral capsule extended release.

Common side effects of Qsymia

Some side effects of phentermine / topiramate may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common

• back pain
• change in taste
• difficulty having a bowel movement (stool)
• ear congestion
• fear or nervousness
• loss of taste
• loss of voice
• memory problems
• pain or tenderness around the eyes and cheekbones
• sneezing
• stuffy or runny nose
• trouble sleeping

Less common

• belching
• cramps
• decreased appetite
• dry eyes
• eye pain
• hair loss
• heartburn or indigestion
• heavy bleeding
• irritability
• pain in the arms or legs
• rash
• stomach discomfort, upset, or pain

Incidence not known

• bloating
• false or unusual sense of well-being
• feeling that others are watching you or controlling your behavior
• feeling that others can hear your thoughts
• feeling, seeing, or hearing things that are not there
• hives or welts
• change in sexual ability, desire, drive, or performance
• severe mood or mental changes
• unusual behavior

Serious side effects of Qsymia

Along with its needed effects, phentermine/topiramate may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking phentermine / topiramate:

Less common

• chest discomfort
• decreased urine
• dry mouth
• fast, irregular, pounding, or racing heartbeat or pulse
• loss of appetite
• mood changes
• muscle pain or cramps
• nausea or vomiting
• numbness or tingling in the hands, feet, or lips
• seizures
• trouble breathing
• unusual tiredness or weakness

Rare

• blood in the urine
• pain in the groin or genitals
• sharp back pain just below the ribs

Incidence not known

• blistering, peeling, or loosening of the skin
• blisters on the mouth, trunk, scalp, or other areas
• blurred or decreased vision
• chest pain
• chills or shivering
• clumsiness
• continuing nausea or vomiting
• cough or sore throat
• dark urine
• diarrhea or light-colored stools
• dizziness
• headache
• increase in the frequency of seizures
• irregular heartbeat
• itching
• joint or muscle pain
• loss of appetite
• low body temperature
• muscle aches or weakness
• pain in the shoulders, arms, jaw, or neck
• red skin lesions, often with a purple center
• red, irritated eyes
• shakiness in the legs, arms, hands, or feet
• sores, ulcers, or white spots in the mouth or on the lips
• sweating
• swelling of the face
• tiredness and weakness
• trouble thinking, speaking, or walking
• upper right abdominal or stomach pain
• weak or feeble pulse
• weight gain
• yellow eyes or skin

For healthcare professionals

Applies to phentermine / topiramate: oral capsule extended release.

General

The most common adverse reactions in adult patients were paresthesia, dizziness, dysgeusia, insomnia, constipation, and dry mouth. The most common adverse reactions in pediatric patients aged 12 years and older were depression, dizziness, arthralgia, pyrexia, influenza, and ligament sprain.^[Ref]

Cardiovascular

• Very common (10% or more): Increased heart rate (up to 77.7%)
• Common (1% to 10%): Palpitations

Phentermine:

• Postmarketing reports: Elevated blood pressure, ischemic events

In clinical trials, a higher incidence of heart rate elevations was observed with this combination drug compared to placebo. In adult patients receiving phentermine 3.75 mg-topiramate 23 mg, increased heart rate greater than 5, 10, 15, and 20 beats per minute (bpm) occurred in 70%, 50%, 32.9%, and 15% of patients, respectively. In adult patients receiving phentermine 7.5 mg-topiramate 46 mg, increased heart rate greater than 5, 10, 15, and 20 bpm occurred in 74.7%, 50.4%, 33.1%, and 13.5% of patients, respectively. In adult patients receiving phentermine 15 mg-topiramate 92 mg, increased heart rate greater than 5, 10, 15, and 20 bpm occurred in 77.7%, 56.1%, 37.3%, and 19.6% of patients, respectively. In pediatric patients receiving phentermine 7.5 mg-topiramate 46 mg, increased heart rate greater than 5, 10, 15, and 20 bpm occurred in 70.4%, 55.6%, 33.3%, and 18.5% of patients, respectively. In pediatric patients receiving phentermine 15 mg-topiramate 92 mg, increased heart rate greater than 5, 10, 15, and 20 bpm occurred in 81.4%, 64.6%, 42.5%, and 23.9% of patients, respectively.

Dermatologic

• Common (1% to 10%): Alopecia, rash

Phentermine:

• Postmarketing reports: Urticaria

Topiramate:

• Frequency not reported: Oligohidrosis
• Postmarketing reports: Bullous skin reactions (including erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis), pemphigus

Oligohidrosis (decreased sweating), infrequently resulting in hospitalization, has been associated with topiramate. Decreased sweating and elevated body temperature above normal characterized these cases. Some cases were reported with topiramate after exposure to elevated environmental temperatures.

Gastrointestinal

• Very common (10% or more): Dry mouth (up to 19%), constipation (up to 16%)
• Common (1% to 10%): Nausea, diarrhea, dyspepsia, gastroesophageal reflux disease, gastroenteritis, oral paresthesia
• Frequency not reported: Upper abdominal pain

Topiramate:

• Postmarketing reports: Pancreatitis

Genitourinary

• Common (1% to 10%): Urinary tract infection, dysmenorrhea

Phentermine:

• Postmarketing reports: Impotence

Hepatic

Topiramate:

• Postmarketing reports: Hepatic failure (including fatalities), hepatitis

Metabolic

• Very common (10% or more): Decreased serum bicarbonate (up to 12.8%)
• Common (1% to 10%): Hypokalemia, decreased appetite
• Uncommon (0.1% to 1%): Markedly low serum bicarbonate values

Topiramate:

• Postmarketing reports: Hyperammonemia (with or without encephalopathy), hypothermia

In 1-year controlled trials of this combination drug, persistent decreases in serum bicarbonate below the normal range (levels of less than 21 mEq/L at 2 consecutive visits/at the final visit) occurred in 6.4% and 12.8% of adult patients with phentermine 7.5 mg-topiramate 46 mg and phentermine 15 mg-topiramate 92 mg, respectively. The incidence of persistent, markedly low serum bicarbonate values (levels of less than 17 mEq/L on 2 consecutive visits/at the final visit) was 0.2% for phentermine 7.5 mg-topiramate 46 mg and 0.7% for phentermine 15 mg-topiramate 92 mg. In a pediatric clinical trial, 60% to 70% of patients treated with this combination drug had a persistent bicarbonate level below the normal range (less than 21 mEq/L) compared to 43% of placebo-treated patients.

Hyperammonemia (with or without encephalopathy) has been reported with topiramate; the risk for hyperammonemia with topiramate appeared dose related and was reported more often when coadministered with valproic acid. In clinical trials of another condition, hyperammonemia occurred in 26% and 14% of pediatric patients (aged 12 to 17 years) taking topiramate 100 mg/day and 50 mg/day; an increased incidence of markedly increased hyperammonemia (50% above the upper limit of normal) also occurred at the 100 mg dose.

Musculoskeletal

• Common (1% to 10%): Back pain, pain in extremity, muscle spasms, musculoskeletal pain, neck pain
• Frequency not reported: Arthralgia, musculoskeletal chest pain, ligament sprain, reduced height velocity, decreased bone mineral density (BMD), reduced bone mineral acquisition

This combination drug has been associated with a reduction in height velocity (cm of height gained per year) in obese pediatric patients aged 12 to 17 years. In a 56-week study, average height increased from baseline in both patients treated with this combination drug and placebo-treated patients; however, a lower height velocity of -1.3 to -1.4 cm/year was observed in patients treated with this combination drug compared to placebo-treated patients.

This combination drug was associated with less bone mineral acquisition in pediatric patients aged 12 to 17 years. In a substudy (n=66) evaluating bone mineralization via dual-energy X-ray absorptiometry (DEXA), increases in BMD at the lumbar spine and total body less head (TBLH) were smaller in pediatric patients treated with this combination drug compared to placebo-treated patients after 1 year of therapy. Declines in BMD Z-scores (standard scores) of -0.5 or greater from baseline for TBLH were observed with phentermine 7.5 mg-topiramate 46 mg (9%) and phentermine 15 mg-topiramate 92 mg (30%). The sample size and study duration were too small to determine if fracture risk was increased. Decreased BMD was not correlated with decreased serum bicarbonate (which commonly occurred with this combination drug) or changes in body weight. No patient had a BMD Z-score that went below -2 during the trial. Similar findings were observed in a 1 year, active-controlled trial of topiramate in pediatric patients with another condition.

Nervous system

• Very common (10% or more): Paresthesia (up to 20%), headache (up to 11%)
• Common (1% to 10%): Dysgeusia, dizziness, hypoesthesia, disturbance in attention
• Frequency not reported: Problems with attention/concentration, problems with memory, problems with language (word-finding)

Phentermine:

• Postmarketing reports: Tremor

In adult clinical trials, paresthesia (characterized as tingling in hands, feet, or face) and dysgeusia (characterized as a metallic taste) were reported. Paresthesia was also reported In pediatric patients.

In 1-year controlled trials of this combination drug, 5% and 7.6% of adult patients reported at least 1 cognitive-related adverse reaction with phentermine 7.5 mg-topiramate 46 mg and phentermine 15 mg-topiramate 92 mg, respectively. These adverse reactions primarily included problems with attention/concentration, memory, and language (word-finding) and occurred at any time during treatment with this combination drug.

Ocular

• Common (1% to 10%): Blurred vision, dry eye, eye pain
• Postmarketing reports: Acute angle closure glaucoma, increased intraocular pressure

Topiramate:

• Postmarketing reports: Maculopathy

Other

• Common (1% to 10%): Fatigue, thirst, procedural pain, chest discomfort, low serum potassium values
• Frequency not reported: Pyrexia, ear infection

In 1-year controlled trials of this combination drug, persistent low serum potassium values (less than 3.5 mEq/L at 2 consecutive visits/at the final visit) during the trial occurred in 3.6% and 4.9% of adult patients with phentermine 7.5 mg-topiramate 46 mg and phentermine 15 mg-topiramate 92 mg, respectively; of those reporting persistent low serum potassium, 88% were receiving treatment with a non-potassium sparing diuretic. The incidence of markedly low serum potassium (less than 3 mEq/L and a greater than 0.5 mEq/L reduction from pretreatment) at any time during the trial was 0.2% for phentermine 7.5 mg-topiramate 46 mg and 0.7% for phentermine 15 mg-topiramate 92 mg. Persistent markedly low serum potassium (less than 3 mEq/L and a greater than 0.5 mEq/L reduction from pretreatment at 2 consecutive visits/at the final visit) occurred in 0.2% and 0.1% of patients receiving phentermine 7.5 mg-topiramate 46 mg and phentermine 15 mg-topiramate 92 mg. Low serum potassium levels (less than 3.5 mEq/L) were not observed in a 56-week clinical trial of pediatric patients with obesity.

Psychiatric

• Very common (10% or more): Mood/sleep disorders (up to 21%), sleep disorders (up to 11%)
• Common (1% to 10%): Insomnia, depression, anxiety, irritability
• Frequency not reported: Mood problems
• Postmarketing reports: Suicidal ideation, suicidal behavior

Phentermine:

• Postmarketing reports: Euphoria, psychosis, changes in libido

In 1-year controlled trials of this combination drug, 15% and 21% of adult patients reported at least 1 adverse reaction related to mood and sleep disorders with phentermine 7.5 mg-topiramate 46 mg and phentermine 15 mg-topiramate 92 mg, respectively; these events were further categorized into sleep disorders, anxiety, and depression. Reports of sleep disorders were generally characterized as insomnia and occurred in 8.1% and 11% of patients treated with phentermine 7.5 mg-topiramate 46 mg and phentermine 15 mg-topiramate 92 mg, respectively. Reports of anxiety occurred in 4.8% and 7.9% of patients treated with phentermine 7.5 mg-topiramate 46 mg and phentermine 15 mg-topiramate 92 mg, respectively. Reports of depression/mood problems occurred in 3.8% and 7.6% of patients treated with phentermine 7.5 mg-topiramate 46 mg and phentermine 15 mg-topiramate 92 mg, respectively. Mood and sleep disorder adverse reactions occurred in patients with and without history of depression.

In a pediatric clinical trial, more patients treated with this combination drug reported at least 1 adverse reaction related to mood (e.g., depression, anxiety) and sleep disorders (e.g., insomnia) compared to placebo-treated patients.

Renal

• Common (1% to 10%): Nephrolithiasis, increased serum creatinine

In 1-year controlled trials of this combination drug, nephrolithiasis was reported in 0.2% and 1.2% of adult patients treated with phentermine 7.5 mg-topiramate 46 mg and phentermine 15 mg-topiramate 92 mg, respectively.

In 1-year controlled trials of this combination drug, serum creatinine increased from baseline, peaking between Week 4 to 8 in adult patients and at Week 16 in pediatric patients; serum creatinine values declined but remained elevated over baseline over 1 year of therapy. The incidence of increases in serum creatinine of at least 0.3 mg/dL at any time during therapy in adult patients was 7.2% for phentermine 7.5 mg-topiramate 46 mg and 8.4% for phentermine 15 mg-topiramate 92 mg; 17% of pediatric patients treated with phentermine 7.5 mg-topiramate 46 mg or phentermine 15 mg-topiramate 92 mg had a serum creatinine at least 0.3 mg/dL at any time post-randomization. Increases in serum creatinine of at least 50% over baseline occurred in 2% and 2.8% of adult patients receiving phentermine 7.5 mg-topiramate 46 mg and phentermine 15 mg-topiramate 92 mg, respectively.

Respiratory

• Very common (10% or more): Upper respiratory tract infection (up to 16%), nasopharyngitis (up to 13%)
• Common (1% to 10%): Sinusitis, bronchitis, cough, influenza, pharyngolaryngeal pain, nasal congestion, sinus congestion

Frequently asked questions

• How Does Qsymia work for weight loss?

Further information

Qsymia side effects can vary depending on the individual. Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.

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