Comparing Contrave vs Phentermine

Contrave vs. Phentermine: A Comparison

Contrave and Phentermine are both FDA-approved weight loss medications with distinct mechanisms: Contrave, combining naltrexone and bupropion, reduces appetite and cravings, while Phentermine decreases appetite and boosts energy by stimulating the central nervous system. While both have proven effective in clinical trials, only Contrave is approved for long-term use.

Comparing Contrave vs Phentermine

Too busy for the full read? Here’s what you need to know:

  • Both Contrave and Phentermine are weight loss medications.
  • Contrave is designed to reduce appetite and control cravings, while Phentermine reduces appetite and boosts energy levels.
  • Contrave doesn’t boost energy levels or speed up metabolism as Phentermine does.
  • Contrave can be taken long-term, whereas Phentermine is often only prescribed for three months at a time.
  • Both medications have potential side effects, and the choice between them depends on an individual’s health circumstances.
  • Phentermine is available in a less expensive generic form.

If you are considering trying a medication to help you lose weight, the choice of treatments can seem overwhelming.

As part of our series on common weight loss drugs, we will explore the benefits and drawbacks of Contrave vs. phentermine so that you can decide if one of these tablets might suit you.

What is Contrave?

Contrave is a medication to treat obesity.

It contains two drugs, namely naltrexone, and bupropion, and should be taken in conjunction with a reduced-calorie diet and regular exercise.

When used alone, naltrexone is used to treat addiction, whereas bupropion is an antidepressant. In combination, these drugs can reduce your appetite, control cravings, and help you to feel fuller sooner. This makes it easier to eat less and therefore lose weight.

Contrave is only prescribed for adults whose body mass index (BMI) is 30 or higher or those with a BMI of 27 or above who also have a weight-related medical complication such as high cholesterol or type 2 diabetes. (1)

This tablet medication is only available on prescription.

Contrave Pill Picture
Image of Contrave tablet

When starting Contrave, a schedule is followed which ensures the dose is gradually increased for four weeks before reaching the recommended dose.

The full daily dosage is two tablets taken twice daily, equivalent to 32mg of naltrexone and 360mg of bupropion.

If Contrave successfully aids weight loss, it can be taken for a year or more. (2)

In clinical trials, those taking Contrave lost two to four times more weight than participants trying to lose weight with diet and exercise alone. (3)

What is Phentermine?

Phentermine is an FDA-approved prescription drug that aids weight loss in adults by reducing appetite and boosting energy levels.

The key ingredient is phentermine hydrochloride, and it is prescribed as a generic pill or under the brand name Adipex-P or Lomaira. (4)

The best results will be seen when this medication is taken with a hypocaloric diet and increased physical activity.

Phentermine stimulates the central nervous system, encouraging the release of neurotransmitters such as epinephrine. This induces a flight or fight response which increases the heart rate, reduces the appetite, and provides extra energy. (5)

Phentermine is available in various doses as a tablet, capsule, and extended-release capsule.

Pills Picture Phentermine
Picture of Adipex-P (left) and generic phentermine (right)

The dosing schedule can vary from one to three times daily, and your doctor will decide the best dose and frequency to suit you. Phentermine is often only prescribed for 12 weeks at a time. (5)

In a clinical trial, participants who took 37.5mg of phentermine for 12 weeks showed a clinically significant reduction in weight and waist circumference and improved cholesterol levels. More than half of those taking the medication lost 10% or more of their baseline body weight during the trial. (6)

Phentermine vs. Contrave: A Comparison

Contrave and phentermine both aid weight loss, but each medication has a different mechanism of action.

Our Contrave vs. phentermine side-by-side table will help you to understand the similarities and differences between the two prescription drugs.

Which is Better: Contrave or Phentermine?

Contrave contains two medications (naltrexone and bupropion) which work by reducing appetite and cravings. Phentermine’s main ingredient, phentermine HCL, stimulates the central nervous system to decrease appetite and increase heart rate and energy levels.

Both medications have been proven to aid weight loss in clinical trials.

At its full dose, some people find it convenient that phentermine only needs to be taken once daily. By comparison, two Contrave tablets should be taken twice a day.

Contrave is approved for longer-term use than phentermine, although some doctors may choose to prescribe 12-week courses of phentermine concurrently if it is successfully aiding weight loss. Unlike phentermine, there is no approved generic version of Contrave available, making it the more expensive of the two.

Both weight loss medications have possible side effects and can cause adverse clinical events in rare cases. It is, therefore, important that you and your doctor decide which drug will offer the greatest chance of weight loss with the lowest chance of complications based on your personal health circumstances.


Which medication is more effective for weight loss, Contrave or Phentermine?

Both Contrave and Phentermine have been found effective in clinical trials, but studies suggest that more participants lost a higher percentage of their baseline weight with Phentermine.

How much weight will you lose on Contrave vs. Phentermine?

In clinical trials, people taking Contrave have seen a 4% to 8% weight loss compared to their baseline body weight (3). In comparison, 50% of participants taking phentermine lost 10% or more of their baseline body weight during a clinical trial. (6)

Can you take Contrave and phentermine together?

You shouldn’t combine phentermine with any other weight loss medication, such as Contrave, as these combinations haven’t been studied enough. We recommend you talk to your healthcare provider about safe options.

Does Contrave give you energy like phentermine?

No, Contrave doesn’t boost energy levels. Contrave is a blend of naltrexone and bupropion and is thought to reduce feelings of hunger and control appetite.

Does Contrave speed up metabolism like phentermine?

No, Contrave doesn’t affect the metabolism. It raises the levels of dopamine to reduce hunger and control cravings.

Which drug is more expensive, Contrave or Phentermine?

Contrave is generally more expensive than Phentermine, particularly because Phentermine is available in a generic form, which tends to be cheaper.

Does insurance cover Contrave or Phentermine?

Some insurance plans may cover Contrave and Phentermine. However, the coverage will depend on your specific plan, and you should check with your insurance provider to confirm.


1. (Contrave).
2. (Contrave Indications).
3. (Contrave FAQs).
4. (Phentermine).
5. (About Phentermine).
6. Kim, K. K. et al. Effects on weight reduction and safety of short-term phentermine administration in Korean obese people. Yonsei Medical Journal. 2006; 47 (5): 614–625. 
7. (Phentermine). 
8. (Naltrexone Injection)
9. Patel, K. et al. Bupropion: a systematic review and meta-analysis of effectiveness as an antidepressant. Therapeutic advances in psychopharmacology. 2016; 6(2): 99–144. 
10. (Currax and Nalpropion).
11. (Phentermine Dosage). 
12. Early J. et al. Naltrexone/Bupropion (Contrave) for Weight Loss. American Family Physician. 2015; 91 (8): 554-546. 
13. (Purchase Contrave).
14. (Contrave Purchasing FAQs).
15. (Contrave Prescription).
16. (Purchase Contrave).
17. (Purchase Generic Adipex-P).
18. (Generic Contrave).