Can phentermine cause heart failure? Risks, long-term effects and more

ByDonald L. Leech

Jun 17, 2022

A link may exist between phentermine and heart failure. Valvular heart disease has been reported rarely in people who have taken this anti-obesity drug.

Valvular heart disease involves damage to one or more of the heart’s valves. These valves open and close to regulate blood flow.

In addition, phentermine can cause another equally serious side effect: pulmonary hypertension. This is high blood pressure in the arteries of the lungs.

People with cardiovascular disease or conditions affecting the heart and lungs should not take phentermine.

This article discusses the association between phentermine and heart failure. It also looks at who shouldn’t take the drug, other risks, and alternative help for obesity.

Phentermine is a brain and spinal cord stimulating drug. It can suppress a person’s appetite, which makes it popular as a weight-loss drug.

In 1959, phentermine first appeared on the market as part of a combination drug for obesity. Then, in the 1980sresearchers found that phentermine and fenfluramine – another appetite suppressant – had a synergistic effect when a person took them together.

This means that their combined effect was greater than the sum of their two separate effects. At that time, the drug combination “fen-phen” became a mainstay in the treatment of obesity.

However, fen-phen had a strong link with pulmonary hypertension and valvular heart disease. The researchers also found a link between fenfluramine alone and these two conditions.

Consequently, the Food and Drug Administration (FDA) banned fenfluramine in 1997, but it continues to allow short-term use of phentermine.

Sometimes doctors prescribe phentermine alone. Alternatively, they prescribe a combination drug containing topiramate, an anticonvulsant. The possibility of heart failure differs when taking phentermine alone and when taking the combined drug.


Experts cannot rule out a link between phentermine alone and heart valve disease. There have been rare reports of the condition manifesting in people who have taken it.

Combination of phentermine and topiramate

The combination of phentermine and topiramate can increase resting heart rate up to 20 beats per minute (bpm). This means that someone who normally has a resting heart rate of 75 bpm would have a resting heart rate as high as 95 bpm.

Despite this adverse effect, the product label does not mention a risk of heart valve disease, as in phentermine alone.

Also, the combination of phentermine and topiramate can cause serious interactions with other drugs that can affect the heart. For example, when a person takes it with a selective serotonin reuptake inhibitor (SSRI) drug, it can cause serotonin syndrome. it can be very dangerous.

People with cardiovascular disease have a higher risk of cardiac side effects, so they should not take phentermine. This includes those who have:

Researchers cannot rule out an association between phentermine alone and pulmonary hypertension, a rare but often fatal disease. A person should stop taking phentermine if they develop symptoms such as difficulty breathing, chest pain, fainting, or swelling in the legs.

Besides the possibility of pulmonary hypertension and valvular heart disease, phentermine has the following health risks:

  • This can impair the ability to engage in hazardous activities: A person may not be able to operate machinery or drive a motor vehicle safely.
  • A person can develop a tolerance: This means that an individual may need a larger dose to receive the same effect. It is dangerous to exceed the recommended dose.
  • This can lead to abuse and addiction: Since phentermine is chemically related to amphetamine, it has these dangers.
  • It interacts negatively with alcohol: Individuals should not consume alcoholic beverages while taking phentermine.
  • It interacts negatively with certain drugs: People should not take other weight loss products or SSRIs while taking phentermine.

Although the FDA has approved phentermine for short-term use, more clinical trials regarding its long-term safety for use for 6 months or more are needed, notes a former 2014 study. Research on cardiovascular effects after more than a year of use is particularly sparse.

Here are some possible alternatives to phentermine.


Acupuncture is an alternative treatment that involves inserting fine needles into pressure points on the body.

A 2018 report assessed 21 studies involving 1,389 participants on the value of acupuncture for obesity. The authors concluded that it was a safe and effective treatment, but longer-term research is needed.

mediterranean diet

Doctors do not advise following fad diets for weight loss, as they are often unhealthy and unsustainable. However, nutritious and balanced diets such as the Mediterranean diet can lead to sustained and lasting weight loss.

The diet includes foods rich in nutrients and fiber, such as fruits, vegetables, nuts and whole grains. It also includes olive oil and oily fish.

Older research since 2010 assessed the effectiveness of the Mediterranean diet in preventing obesity in 10,376 participants. The authors concluded that it may slow age-related weight gain. Because the diet has a high palatability, it has strong adherence potential.

Other anti-obesity drugs

Besides phentermine, there are other anti-obesity drugs available. These to understand:

  • orlistat (Xenical), which reduces fat absorption
  • naltrexone-bupropion (Contrave), which decreases appetite or promotes feelings of fullness
  • liraglutide (Saxenda) or semaglutide (Wegovy), which mimics a hormone that can regulate appetite
  • setmelanotide (Mcivree), which may decrease appetite, increase feelings of fullness, and increase metabolism

However, it is important to note that all of the above have side effects and risks, some of which can be serious. If a person’s doctor thinks they should take obesity medication, they will prescribe the correct medication and dose.

weight loss surgery

Bariatric surgery may be an option for people with a body mass index of 35 or more. It promotes weight loss by making changes to a person’s digestive system. A common type, bariatric surgery, works by dividing the stomach to create a smaller upper pouch.

Options have a short term Side effects and long-term risks. However, when other medications and weight loss diets have not produced adequate results, doctors may consider surgery. A person must stick to a sustainable diet and exercise program to maintain their results.

The possible link between phentermine and heart failure stems from rare reports of valvular heart disease in people who took the drug. The drug can also cause pulmonary hypertension, which can be fatal.

Sometimes, instead of prescribing phentermine alone, doctors prescribe a drug that combines phentermine with topiramate. This combination can increase heartbeat.

If a person has any type of cardiovascular disease, they should not take phentermine. Also, before someone takes phentermine, they should disclose to their doctor what other medications and supplements they are taking to ensure that there is no risk of harmful interactions.