phendimetrazine
Phendimetrazine, formerly known as brand-name medication Bontril, is a prescription sympathomimetic medication typically used in combination with diet and exercise. It works as an appetite suppressant in the brain to help adults with weight loss. It's available as an immediate-release tablet taken by mouth two to three times per day, and an extended-release capsule taken once per day. Side effects include restlessness, headache, and high blood pressure.
What is Phendimetrazine?
What is Phendimetrazine used for?
Short-term treatment for weight management in adults with a body mass index (BMI) of:
30 kg/m2 or greater; or
27 kg/m2 or greater with other risk factors (e.g., high blood pressure, high blood sugar, high cholesterol)
How Phendimetrazine works
Phendimetrazine is a sympathomimetic. The exact way it helps with weight loss isn't well understood. But it's thought to lower your appetite by working in the part of your brain that controls hunger.
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What are the risks and warnings for Phendimetrazine?
Phendimetrazine 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.
Not safe with other weight loss medications
Phendimetrazine shouldn't be taken along with other medications for weight loss, including ones found over the counter. Talk with your care team if you have more questions about your treatment plan.
Lower response to the medication over time
Phendimetrazine might stop working as well over time, even for those who saw good results at the start. This is called tolerance. Raising the dose of phendimetrazine won't help and isn't safe because of the risk for serious side effects. Let your prescriber know if you've noticed weight gain or your appetite returning after you've been taking this medication. They'll need to recommend other treatment options for you.
Risk of misuse and dependence
Risk factors: Taking more phendimetrazine than prescribed
Similar to other stimulants, phendimetrazine has a risk of misuse and for causing dependence, which can lead to stimulant use disorder. To lower this risk, your healthcare professional will usually prescribe a limited amount at a time. Take phendimetrazine exactly as directed. It's meant for short-term use, typically just a few weeks. If interested, talk with your care team to learn more about long-term weight management options.
High blood pressure in the lungs (pulmonary hypertension)
Risk factors: Taking phendimetrazine for longer than 3 months
Although rare, phendimetrazine can cause pulmonary hypertension, or high blood pressure in the lungs. Pulmonary hypertension is serious and can be life-threatening. The risk is higher if you take medications that lower your appetite, including phendimetrazine, for longer than 3 months. If you experience trouble breathing, chest pain, fainting, or swelling in your legs, stop the medication and get medical help right away.
Heart valve problem
Risk factors: Long-term use | Taking high doses | Taking multiple medications that lower your appetite
People taking stimulants similar to phendimetrazine experienced heart valve problems.The risk is higher for those using the medication long-term or taking multiple appetite-suppressing medications. Let your prescriber know if you have dizziness, chest pain, leg or ankle swelling, irregular heartbeat, fatigue, or trouble breathing.
Risk of high blood pressure
Let your prescriber know if you have high blood pressure, even if your condition is well-controlled by medications. Taking phendimetrazine might raise your risk for high blood pressure so your care team might ask you to check your blood pressure more often during treatment.
Risk of low blood sugar in people with diabetes
Risk factors: Taking insulin or sulfonylureas
People with diabetes who are taking medications that lower blood sugar, such as insulin or sulfonylureas like glipizide, are at higher risk for low blood sugar during treatment with phendimetrazine. This can happen due to changes in eating habits and appetite with phendimetrazine. Your diabetes care team might need to adjust the dose of your blood sugar medications after you start phendimetrazine.
Always keep emergency glucose tablets or hard candy with you in case your blood sugar drops too low. If you experience symptoms of low blood sugar, such as feeling faint, shaking, and sweating, check and treat your low blood sugar levels right away. If your symptoms don't improve, get medical help.
What are the side effects of Phendimetrazine?
Common Side Effects
- Fast heartbeat
- High blood pressure
- Restlessness
- Trouble sleeping
- Nervousness
- Shakiness
- Sweating
Other Side Effects
- Dizziness
- Headache
- Blurry vision
- Nausea
- Diarrhea
- Constipation
- Stomach pain
- Dry mouth
- Frequent or painful urination
- Changes in your sex drive
Serious Side Effects
- Heart valve problems: dizziness, chest pain, leg or ankle swelling, irregular heartbeat, fatigue, trouble breathing
- High blood pressure in the lungs: trouble breathing, chest pain, fainting, swelling in the legs
Source:Â DailyMed
The following side effects have also been reported
Along with its needed effects, a medicine 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:
Rare
Seeing, hearing, or feeling things that are not there
severe mental changes
Incidence not known
burning while urinating
chest pain or discomfort
decreased ability to exercise
difficult or painful urination
dizziness
fainting
fast, irregular, pounding, or racing heartbeat or pulse
feeling of warmth
headache
hyperventilation
increased need to urinate
irritability
numbness or tingling in the arms or legs
pain or discomfort in the arms, jaw, back, or neck
passing urine more often
redness of the face, neck, arms, and occasionally, upper chest
restlessness
shakiness in the legs, arms, hands, or feet
shortness of breath
sweating
swelling of the feet or lower legs
trembling or shaking of the hands or feet
trouble with breathing
trouble with sleeping
trouble with thinking, speaking, or walking
vomiting
weakness
Get emergency help immediately if any of the following symptoms of overdose occur:
Symptoms of overdose
Abdominal or stomach cramps
blurred vision
change in consciousness
convulsions
discouragement
dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position
fast, slow, or irregular heartbeat
feeling sad or empty
lack of appetite
lightheadedness
loss of consciousness
loss of interest or pleasure
overactive reflexes
panic
physical attempt to injure
pounding in the ears
rapid breathing
sweating
tiredness
trouble with concentrating
unusual tiredness or weakness
violent actions
Some side effects 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:
Incidence not known
Decreased interest in sexual intercourse
difficulty having a bowel movement (stool)
inability to have or keep an erection
increased in sexual ability, desire, drive, or performance
increased interest in sexual intercourse
loss in sexual ability, desire, drive, or performance
stomach pain
unable to sleep
Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.
Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.
Pros and cons of Phendimetrazine
Pros
Comes in immediate-release and extended-release forms
Available as a lower-cost generic form
Cons
Risk of misuse and dependency
Typically recommended to be used for a short period of time (a few weeks)
Pharmacist tips for Phendimetrazine
You'll take phendimetrazine differently depending on the form you're prescribed. For the immediate-release tablet, take it 2 or 3 times a day as directed, 1 hour before a meal. For the extended-release capsule, take it 30 to 60 minutes before breakfast.
Use Phendimetrazine along with diet and exercise to help you lose weight more effectively. Work with your care team to come up with a plan for a healthy diet and regular exercise that works best for you.
Avoid alcohol while taking phendimetrazine as it can make the side effects worse.
Since phendimetrazine affects the brain, it can make tasks like driving harder. Avoid certain activities until you know how this medication affects you.
Phendimetrazine reduces your appetite, raising your risk of low blood sugar (hypoglycemia). If you have diabetes and take medications like insulin or glipizide, let your prescriber know. They might need to adjust your medication dose.
Phendimetrazine interacts with several medications, such as monoamine oxidase inhibitors (MAOIs). Tell your care team know about all the medications you're taking before starting phendimetrazine, as well as any you plan to take during treatment. They can make sure your medications are safe for you.
Weight loss medications like phendimetrazine must be avoided during pregnancy. Weight loss during pregnancy can cause harm to unborn babies. If you're pregnant or planning to be, tell your prescriber right away, as you'll need to stop using this medication.
It's not known if phendimetrazine is safe to take while breastfeeding. Similar stimulants pass into breast milk and can potentially cause serious side effects in your baby. Talk to your prescriber or OB-GYN about the risks and benefits of taking this medication while breastfeeding.
Frequently asked questions about Phendimetrazine
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Phendimetrazine dosage forms
| Dosage | Quantity | Price as low as | Price per unit |
|---|---|---|---|
| 35mg | 90 tablets | $16.30 | $0.18 |
Typical dosing for Phendimetrazine
Immediate-release tablets (35 mg): The typical dose is 1 tablet by mouth two or three times per day, 1 hour before meals. The maximum dose is 2 tablets three times per day.
Extended-release capsules (105 mg): The typical dose is 1 capsule by mouth every morning, 30 to 60 minutes before a meal.
Interactions between Phendimetrazine and other drugs
Using this medicine with any of the following medicines is not recommended. Your doctor may decide not to treat you with this medication or change some of the other medicines you take.
- Brofaromine
- Clorgyline
- Furazolidone
- Iproniazid
- Isocarboxazid
- Lazabemide
- Linezolid
- Moclobemide
- Nialamide
- Pargyline
- Phenelzine
- Procarbazine
- Rasagiline
- Selegiline
- Sibutramine
- Toloxatone
- Tranylcypromine
Using this medicine with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.
- Iobenguane I 131
How much does Phendimetrazine cost?
Phendimetrazine contraindications
Heart problems (e.g., coronary artery disease, stroke, irregular heartbeat, uncontrolled high blood pressure, congestive heart failure)
Currently take or have taken a monoamine oxidase inhibitors (MAOI) in the last 14 days
Using other weight-loss medications
Overactive thyroid (hyperthyroidism)
Feeling agitated or distressed
History of substance use disorder
Currently pregnant or breastfeeding
What are alternatives to Phendimetrazine?
Short-term treatment for weight management in adults with a body mass index (BMI) of:
30 kg/m2 or greater; or
27 kg/m2 or greater with other risk factors (e.g., high blood pressure, high blood sugar, high cholesterol)
30 kg/m2 or greater; or
27 kg/m2 or greater, and with at least one other weight-related condition (e.g., high blood pressure, high blood sugar, high cholesterol)
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References
Best studies we foundAcertis Pharmaceuticals, LLC. (2023). Phendimetrazine tartrate capsule, extended release [package insert]. DailyMed.
American Thyroid Association. (n.d.). Hyperthyroidism.
Apovian, C. M., et al. (2015). Pharmacological management of obesity: An Endocrine Society Clinical Practice Guideline. The Journal of Clinical Endocrinology & Metabolism.
Centers for Disease Control and Prevention. (1997). Cardiac valvulopathy associated with exposure to fenfluramine or dexfenfluramine: U.S. Department of Health and Human Services Interim Public Health Recommendations, November 1997. Morbidity and Mortality Weekly Report.
KVK-TECH, INC. (2024). Phendimetrazine tartrate tablet [package insert]. DailyMed.
MedlinePlus. (2024). Heart valve diseases.
National Institute on Drug Abuse. (2011). Misuse of prescription drugs research report: Overview.
Pilitsi, E., et al. (2019). Pharmacotherapy of obesity: Available medications and drugs under investigation. Metabolism.
World Health Organization. (2009). 4 Withdrawal management. Clinical Guidelines for Withdrawal Management and Treatment of Drug Dependence in Closed Settings.
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