Phentermine vs Contrave: What’s better? (best together?)

January 9, 2024 |

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This article will give you all the information about Phentermine and Contrave. So, you could decide on the best diet pill to help you lose weight.

Both these appetite suppressants are effective for reducing food cravings and calorie intake.

However, Phentermine is a short-term appetite suppressant medication promising quick results, while Contrave offers relatively slower weight loss and so is prescribed for long-term usage.

In the following sections, we have described the mode of action for these medicines and their side effects on your body.

To make the decision easier for you, we have also included their efficacy reports from clinical trials and user reviews as well.

So, read till the end to get all the details about these two weight loss medicines.

Starting with a brief ingredient analysis to see how these drugs work;

What is Phentermine?

Phentermine formula

Phentermine is a sympathomimetic amine prescribed as an anorectic drug to overweight persons who struggle with binge eating.

This compound act as a nervous system stimulator, inducing appetite suppression and increased energy expenditure at rest.

This diet supplement is used for short-term (not more than 12 weeks) weight loss therapies. Usually, it is sold in the market under the names Phentermine HCL, Adipex-P, and Lomaira.

Because it is a prescription drug, you can only buy it with a recommendation from your physician.

In most cases, doctors prescribe it for a few weeks depending upon the health condition and lifestyle of the patient.

Coming to its mode of action, Phentermine targets synaptic receptors in the central nervous system to raise the level of certain neurotransmitters (dopamine, norepinephrine).

In turn, these neuromodulatory molecules induce hunger suppression and make you feel “full” for a long time.

What is Contrave?

Contrave is also another prescription supplement for weight loss.

It was initially formulated by Orexigen Therapeutics, later on, acquired by Nalpropion Pharmaceuticals in 2018, and then by Currax Pharmaceuticals in 2019.

Currax is a US-based pharmaceutical company focused on developing, acquiring, and commercializing specialty medicines. 

This pharma has earned a good reputation in a short time for its effective prescription drugs, and Contrave is the topmost of these products.

It is a combination of bupropion HCl and naltrexone HCl, usually prescribed to people having a body mass index (BMI) of 30 kg/m2 or above.

These ingredients are also separately used to treat physical and mental health issues. Bupropion is primarily used as an antidepressant, and its monotherapy is also prescribed to help people with weight loss.

Naltrexone is an opioid antagonist used to reduce cravings in patients with alcohol or opioid use disorder.

Its ability to suppress cravings also helps curb eating desire, making it a suitable ingredient for diet pills.

These molecules stimulate two parts of the central nervous system (the Hypothalamus and mesolimbic system) to reduce appetite and food cravings, helping you reduce your calorie intake.

However, each ingredient affects the brain in a different but synergistic way to lower the urge to eat.

Bupropion stimulates POMC neurons in the Hypothalamus to release hunger-reducing neurotransmitters, but this secretion can stop when your stomach is empty.

Here, Naltrexone comes into play and blocks the feedback receptors of these neurons to ensure a consistent release of hunger-reducing substances.

Similarly, these compounds affect the limbic reward system in the brain to reduce food cravings, but the exact neurochemical effects are not entirely understood yet.

Phentermine vs. Contrave – Which one is safer & effective?

Both diet pills promise great results, but which one should you choose? And are these anorectic drugs safe in the first place?

To eliminate these confusions, we have compiled their benefits, side effects, and user reviews for you to make an informed decision.

1. Benefits

Phentermine benefits

The number one benefit you get from Phentermine is obviously the loss of appetite and a constant satisfaction that keeps you from eating even when presented with delicious meals.

This satisfactory feeling results from high dopamine levels, while appetite loss is primarily due to the stress response induced by norepinephrine.

As a result, its hunger-curbing effects are significant. Plus, these effects persist for 2 to 3 days as the drug’s half-life is 19-24 hours.

According to a research journal, most individuals who used phentermine HCl 37.5 mg during a 12-week clinical trial significantly reduced weight, waist circumference, and cholesterol levels.

Over 80% of these participants lost 5% of their initial weight, and more than half reported up to 10% weight loss.

Plus, Phentermine has mild positive effects on metabolism.

These effects are credited to its thermogenic (heat-producing) properties. As a result, metabolic reactions speed up when the body’s temperature is slightly raised.

Moreover, evidence from research infers that energy expenditure at rest increases by 35% after taking Phentermine, eventually leading to an increased fat loss.

Another advantage that you get with Phentermine is a mood and energy boost. And the credit here also goes to dopamine which also has the nickname “feel-good hormone” because it makes you happier, satisfied, and energetic.

Now let’s see what good does Contrave offers?

Contrave benefits

As we mentioned earlier, contrave targets two different brain areas.

Its activity on hypothalamus neurons inactivates the automatic hunger response when your stomach is empty and your body needs energy.

Thus, it makes your brain unaware of your lower calorie intake.

Besides the Hypothalamus, it also affects mesolimbic brain circuits (this system perceives fats and a carb-rich diet as a reward and makes you crave such food in the future).

Its influence on mesolimbic nerves benefits in two ways;

On one side, it reduces the craving for starchy and fatty foods like ice creams, chocolates, sweets, fried items, and fast food snacks.

While on the other side, increased dopamine induces a feeling of fullness even when you have taken just a few bites.

Under its influence, your food intake is minimized automatically as you are neither hungry nor craving food.

Clinical reports also confirm the efficacy of this drug.

A placebo-controlled trial from 2010 inferred that bodyweight dropped by 6.1% in Contrave users compared to placebo, who only lost 1.3% of their initial weight.
Plus, this drug also provides the mode improving effects of dopamine surge because Bupropion raises its level in the brain.

So, which to opt for?

Both medicines provide effective hunger control, but Phentermine shows quicker results as its simulative effects are relatively intense.

However, you cannot rely forever upon medicines for effective weight management. Instead, you need to incorporate healthy habits like a balanced diet and regular physical activity for long-term results.

In this respect, Contrave can help you more because it is meant for long-term usage, and you can easily modify your lifestyle and eating habits during this time.

2. Safety of Phentermine and Contrave

How safe is Phentermine?

Both of these pills are FDA-approved as prescription anorectic drugs.

However, Phentermine only has approval for short-term usage (up to three months) as it is a controlled substance and may cause dependence if used for long.

But Contrave can be used for a long time because none of its ingredients come in the “controlled substance” category.

Hence, Contrave weight loss therapies are usually one-year long.

In healthy persons, Phentermine is generally well tolerated. Its safety level is also confirmed by research.

This randomized trial infers that Phentermine was effective for weight reduction and produced only low to moderate intensity side effects in healthy but overweight people.

However, this medicine can cause serious health issues for persons with underlying cardiovascular or cerebral problems and pregnant women.

How safe is Contrave?

Similarly, Contrave is found to be tolerable with mild-intensity adverse effects.

To access its safety level, the health of 3475 individuals taking this medicine was monitored in a clinical trial.

The results have shown nausea (reported by 32.5% of participants), constipation (19.2%), and headache (17.6%) as the most frequent negative outcomes of this drug.

Other adversities were seen in less than 10% of users. Likewise, a negligible risk factor for cardiovascular ailments was indicated in this study.

Nonetheless, both research and the pharma itself state that serious side effects like suicidal thoughts, liver damage, vision problems, or manic behavior may occur after using this anorectic.

In the next section, we have listed the potential negative effects these drugs can cause.

Many of these effects are the same as Naltrexone, Bupropion, and Phentermine; all work by influencing brain cells.

3. Side effects of Phentermine and Contrave

Side effects of Phentermine

Phentermine users commonly complain of nausea, insomnia, headache, dry mouth, palpitations, tachycardia, constipation, and thirst.

  • Severe side effects include pulmonary hypertension, cardiovascular diseases, stroke, dyskinesia, and psychosis.
  • Different case studies enlisted in scientific chronicles indicate that phentermine usage may result in cardiac problems like valvular heart disease, ventricular fibrillation, and heart arrhythmias.
  • Similarly, phentermine usage has been associated with cerebral stroke, tardive dyskinesia, and Parkinsonism in people with a predisposition for brain diseases like cerebrovascular risk factors or a family history of Parkinson’s disease.
  • Plus, it may lead to psychotic behavior and anti-social thoughts if any person takes high doses or consumes this anorectic for a long time.

Besides that, it is contradicted for women who are either conceiving or planning to conceive because it increases the risk of gestational diabetes, and labor may become complicated by its effects.

Moreover, this anorectic pill can cause abnormalities and disorders in unborn babies like bilateral cysts, prenatal stroke, neural tube defects, etc.

You can check out our other article for complete details of phentermine side effects.

Side effects of Contrave

The common side effects of Contrave are nausea, headache, dry mouth, dizziness, constipation, vomiting, sleep disturbance, and diarrhea.

  • It can also cause serious side effects like depression, mania, hepatitis, angle-closure glaucoma, and severe allergic reactions.
  • Bupropion can induce suicidal thoughts or manic behavior, especially in the initial phase of therapy. Plus, this compound is known to lower the seizure threshold, increasing the risk of seizures.
  • Besides that, this drug can lead to opioid-related issues due to Naltrexone, reducing the efficacy of opioid-based medicines and street drugs.

That is why you should tell your doctor about all the medication you use so he can determine if Contrave is suitable for you or not.

Like Phentermine, this drug is also listed in category X for use during pregnancy.

It is contradicted for mothers-to-be because its effects on the health of gravida and her unborn baby are not known yet.

Likewise, it is not suitable for breastfeeding mothers as both Bupropion and Naltrexone are secreted in milk and may cause harm to the infant.

User reviews of Contrave and Phentermine


Phentermine has been a popular dieting medicine for decades owing to its excellent weight loss results.

Most users start seeing results in the first month of usage with an average monthly weight drop of 4 to 8 pounds.

Moreover, its short-term usage reduces the risk of many adversities. That is why it gets more positive ratings on third-part forums.

On, Phentermine has a rating of 8.7 out of 10, with 84% of reviewers describing a positive experience. Nonetheless, 5% of users also reported a negative experience.

Phentermine user reviews on Drugs

Another health forum, WebMD, lists Phentermine oral with a 4.3 out of 5 rating from users.


Contrave also has positive reviews from most of its users.

Some of these folks found it more effective than Phentermine and mentioned that they lost more than 40 pounds in just three months (that equals more than 13 pounds a month!)

But others were not completely satisfied with the results.
Many users complained about its severe side effects, especially psychotic episodes, and nauseatic feelings.

Most probably, this drug is rated low by consumers due to significant adverse effects.

Contrave has an average rating of 6.9 out of 10 on and 66% of positive reviews. On this forum, 22% of the reviewers mentioned a negative experience with the drug.

Contrave user reviews

On WebMD, it has been rated 3.5 out of 5 for effective weight loss.

On both of these websites, it has fewer reviews than Phentermine.

Cost of Phentermine and Contrave?

Phentermine costs

Phentermine is a relatively cheaper diet supplement. It comes in both capsule (15mg, 30mg, 37.5mg) and tablet (37.5mg) forms.

You can buy these on prescription at different local and online pharmacies within the following price range;

  • 30 tablets of 37.5mg phentermine HCL cost $16.44 to $23.35.
  • 60 tablets of 37.5mg phentermine HCL cost $37.20.
  • 120 tablets of 37.5mg phentermine HCL cost $64.91.

Contrave costs

On the other side, Contrave is available as extended-release oral tablets (Bupropion 90mg/ Naltrexone 8mg).

It usually comes in two packing variations of 70 tablets and 120 tablets.

A bottle of 70 Contrave tablets costs $260.03, and the bottle containing 120 pills comes for $667.84.

Phentermine Pros and Cons


  • Reduce hunger pangs.
  • Induce satisfaction.
  • Improves metabolic rates.
  • Increases energy and happiness.


  • Disturbs sleep.
  • Unfit for pregnancy.
  • Relates to cardiovascular comorbidities.

Contrave Pros and Cons


  • Decreases appetite.
  • Reduces food cravings.


  • may cause seizures.
  • induce suicidal thoughts.
  • can cause hepatitis.
  • Potentially cause vision problems.

FAQs on Contrave vs. Phentermine

How much weight can you lose with Contrave?

On average, a 5 to 10% reduction in initial body weight is expected by using Contrave for 56 weeks.

However, many users have gained much better results; they reported up to 18% weight loss, dropping 30 to 50 pounds in a few months.

Can I take Phentermine with Contrave together?

No, it is not recommended to take these anorectic pills in combination.

Both are psychostimulants, and their combined effects can lead to severe health adversities.

Does Contrave speed up metabolism?

No, Contrave does not affect metabolic reactions.

It will only prevent excessive calorie intake, forcing your body to metabolize stored fats for energy. But it does not speed up the rate of metabolic reactions.


Phentermine and Contrave both show anorectic effects by triggering specific neurons in the brain to release hunger-reducing hormones.

Weight loss with Contrave is a relatively slow process and usually spans up to a year.

On the other side, Phentermine has more potent stimulatory properties, showing a faster reduction in weight.

Safety profiles of both drugs are also matching; however, psychic problems can be more severe with Contrave, while Phentermine can aggravate cardiovascular diseases.

To sum it up, Phentermine seems to be more effective, cheaper, and safer, but it’s best to discuss all the options with your doctor before starting an anorectic medication.

Because only he can provide a better insight by looking at your health condition and the drug’s efficacy.

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