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Contrave vs Phentermine: Comparing Two Popular Weight Loss Medications

Written by Andrew Le, MD

UpdatedFebruary 28, 2024

With obesity impacting over 70% of American adults and rates continuing to climb, many are turning to medications like Contrave and Phentermine for appetite management and weight loss.

These two popular drugs work differently, but both effectively suppress appetite. Contrave makes you feel fuller while decreasing cravings, whereas Phentermine blunts appetite.

In this article, we’ll compare Contrave and Phentermine - their approved uses, weight loss results, dosages, side effects, and costs. Learning the key differences will help determine which option suits your weight loss goals.

🔑 Key Takeaways

  • Contrave is approved for long-term obesity treatment in adults with a BMI over 30, while Phentermine is approved for short-term weight loss in obese adults.
  • Clinical trials show Contrave produces around 5% weight loss when combined with diet and exercise, while studies show Phentermine typically leads to at least 5% weight loss over 12 weeks.
  • The recommended total daily dosage of Contrave is two 8mg/90mg tablets twice daily, while Phentermine dosages vary by form from 15-37mg daily.
  • Common side effects of Contrave include dizziness, headache, and insomnia, while Phentermine may cause more severe side effects like increased blood pressure.
  • Contrave costs $99 monthly through a savings program, while generic Phentermine costs as little as $8.79 with a GoodRx coupon.
  • Contrave seems better for long-term use, while Phentermine produces faster initial weight loss but has more potential side effects.
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1. Approved Uses

Medications like Contrave and Phentermine can be valuable tools for tackling excess weight and improving health. But understanding their approved uses is key. Let’s explore these below.


Contrave is a prescription weight loss medication that contains two primary active ingredients: naltrexone and bupropion.

Naltrexone is an opioid antagonist that reduces food cravings, while bupropion is an antidepressant that can also assist in smoking cessation. When used together, these two components help patients reduce their cravings for food and increase feelings of fullness. This leads to reduced calorie intake and healthy weight loss.

One of its primary approved uses is in the treatment of obesity. It is indicated for use in adults with a BMI of 30 kg/m2 or greater.

Contrave is prescribed to help individuals with obesity manage their weight more effectively, aiming to reduce the health risks associated with this condition.

In addition to treating obesity, Contrave is also approved for overweight individuals with specific weight-related medical conditions. It can be used in overweight adults with a BMI of 27 kg/m2 or greater who have at least one weight-related medical problem.

These weight-related medical conditions may include issues such as:

By helping overweight individuals lose weight, Contrave may assist in improving or managing these associated health problems, which are often exacerbated by excess weight.

It's important to emphasize that Contrave-approved uses are not for cosmetic weight loss but rather for individuals who are at a higher risk due to their obesity or overweight status and related medical complications.

✅ Health Tip

To achieve the best results in weight management, Contrave should be used in conjunction with a reduced-calorie diet and increased physical activity. Patients should work closely with their healthcare provider to determine if Contrave is a suitable option for their specific medical circumstances and weight management needs.


Phentermine is a prescription stimulant medication that acts as an appetite suppressant. It increases the levels of certain neurotransmitters in the brain, including dopamine and norepinephrine.

This helps reduce cravings and hunger, and it also increases heart rate and blood pressure, which can lead to improved physical activity performance and higher energy levels.

Phentermine has several approved uses primarily related to weight management and treating obesity. It is also used as a medical intervention to address the health risks of excess body weight.

The medication is typically prescribed to individuals with a BMI of 30 kg/m2 or greater, indicating obesity. The use of Phentermine aims to assist in achieving weight loss and reducing the associated health risks often accompanying obesity.

In addition to the treatment of obesity, Phentermine is also employed in managing the weight of overweight individuals with a BMI of 27 kg/m2 or greater. This usage is particularly relevant if these individuals have additional risk factors such as:

  • High blood pressure
  • High cholesterol
  • Diabetes

One of the critical characteristics of phentermine's approved use is its designation for short-term intervention.

Phentermine is not meant for long-term use but as part of a temporary regimen. Typically, this regimen includes:

  • Exercise
  • Behavioral modification
  • Caloric restriction

The primary goal during this short-term use is to achieve initial weight loss and establish healthier habits. It is not intended as a cosmetic or long-term weight loss solution.

2. Effectiveness in Weight Loss

With obesity impacting so many individuals, effective medications for weight loss are critical. But how well do Contrave and Phentermine actually work?


Contrave is effective for weight management combined with a balanced diet and exercise. Clinical trials demonstrated that people who took Contrave with a reduced-calorie diet and increased physical activity lost more weight than those who did not.

In the Intent-to-Treat (ITT) population, people taking Contrave experienced a weight loss of approximately 5.4% compared to a 1.3% weight loss in the placebo group. Furthermore, a significant percentage of patients taking Contrave achieved a 5% or greater weight loss, considered clinically significant for health benefits.

The results from the clinical trials suggest that Contrave can be an effective tool for individuals who are struggling with weight management, mainly when used in combination with a balanced diet and exercise.

However, as with any medication, individual responses may vary, and it's essential to consult a healthcare provider to determine if Contrave is a suitable option for your specific weight loss goals and health condition.


One study suggests that phentermine, when administered for a short duration (approximately 12 weeks), can lead to significant weight reduction.

Over 80% of subjects in the Phentermine group experienced a weight loss of 5% or more of their initial weight, and more than half achieved a weight loss of 10% or more. This indicates that Phentermine can help obese individuals reach their initial weight loss goals effectively and rapidly.

Another study further supports the weight loss benefits of phentermine. More than 45% of patients who took phentermine lost at least 5% of their body weight, with an average weight loss of 3.8 kg (8.3 lbs).

Although some patients experienced adverse events, only a tiny percentage (9%) discontinued the medication. This suggests that, on the whole, patients demonstrated good tolerance to phentermine.

3. Dosage Differences

To achieve optimal results, proper dosing of weight loss medications is essential. Here's an overview of the recommended dosages for Contrave and Phentermine.


Contrave is a medication that combines two active ingredients, Naltrexone Hydrochloride and Bupropion Hydrochloride, in a specific dosage. The recommended dosing schedule for Contrave is as follows:

  • Week 1: 1 tablet in the morning and none in the evening
  • Week 2: 1 tablet in the morning and 1 tablet in the evening
  • Week 3: 2 tablets in the morning and 1 tablet in the evening
  • Week 4 and onward: 2 tablets in the morning and 2 tablets in the evening

This schedule leads to a total daily dosage of two Contrave 8 mg/90 mg tablets in the morning and two tablets in the evening, amounting to 32 mg of Naltrexone Hydrochloride and 360 mg of Bupropion Hydrochloride per day.

Contrave should be taken by mouth in the morning and evening, and the tablets should not be cut, chewed, or crushed. It's important to note that total daily doses greater than 32 mg/360 mg per day are not recommended. The medication may be taken with or without meals, but it should not be taken with a high-fat meal.


The dosage of Phentermine may vary depending on the specific form of the medication and the medical condition being treated. For the treatment of obesity, the typical dosages for different forms of Phentermine are as follows:

  • Capsules: For adults and children 17 years and older, the dosage is 15 to 30 milligrams (mg) once a day, taken approximately 2 hours after breakfast. Use in children 16 years of age and younger is not recommended.
  • Disintegrating Tablets: Adults and children 17 years of age and older are typically prescribed one tablet once a day, taken in the morning. Use in children 16 years of age and younger is not recommended.
  • Extended-Release Capsules: For adults and children 16 years of age and older, the usual dosage is one capsule once a day before breakfast or 10 to 14 hours before sleeping. Use in children 15 years of age and younger is not recommended.

It's essential to follow the doctor's instructions regarding the appropriate form and dosage of Phentermine for your specific situation. The dosage may vary based on the strength of the medication and the individual's age and medical condition.

If a dose is missed, it should be taken as soon as possible, but if it's close to the next scheduled dose, it should be skipped. Double doses should not be taken. Proper storage instructions should also be followed, as provided by your healthcare professional.

4. Side Effects

While effective for weight loss, both Contrave and Phentermine can cause side effects that should be considered.


More common side effects:

Less common side effects:

  • Bladder pain
  • Bloody or cloudy urine
  • Difficult, burning, or painful urination
  • Fast, irregular, pounding, or racing heartbeat or pulse
  • Frequent urge to urinate
  • Lower back or side pain
  • Shakiness in the legs, arms, hands, or feet
  • Trembling or shaking of the hands or feet

Less common or rare side effects:

  • Chest pain or discomfort
  • Nausea
  • Pain or discomfort in the arms, jaw, back, or neck
  • Sweating
  • Vomiting
  • Changes in behavior
  • Thoughts of killing oneself
  • Aggressive or angry behavior
  • Anxiety
  • Blistering, peeling, or loosening of the skin
  • Chills
  • Clay-colored stools
  • Cough
  • Dark urine
  • Delusions of persecution, mistrust, suspiciousness, or combativeness
  • Diarrhea
  • Difficulty with moving
  • Difficulty with swallowing
  • Dry mouth
  • False beliefs that facts cannot change
  • Feeling that others are watching you or controlling your behavior
  • Feeling, seeing, or hearing things that are not there
  • Fever
  • Hives, itching, or rash
  • Hyperventilation
  • Joint or muscle pain
  • Significant, hive-like swelling on the face, eyelids, lips, tongue, throat, hands, legs, feet, or sex organs
  • Muscle stiffness
  • Puffiness or swelling of the eyelids or around the eyes, face, lips, or tongue
  • Red, irritated eyes
  • Restlessness
  • Severe mood or mental changes
  • Sore throat
  • Sores, ulcers, or white spots in the mouth or on the lips
  • Stomach pain or tenderness
  • Swelling of the feet or lower legs
  • Tightness in the chest
  • Unusual behavior
  • Yellow eyes or skin

Other side effects:

Some side effects may occur that usually do not need medical attention. These may go away as your body adjusts to the medicine. These side effects include: d

  • Difficulty having a bowel movement
  • Change or loss of taste
  • Continuing ringing or buzzing in the ears
  • Feeling of warmth
  • Hearing loss
  • Increased sweating
  • Redness of the face, neck, arms, and occasionally upper chest
  • Stomach pain

📓 Additional Note

During a placebo-controlled trial, the common side effects of Contrave include nausea, constipation, headache, vomiting, dizziness, insomnia, dry mouth, and diarrhea. Additionally, naltrexone/bupropion has been associated with increased resting heart rate and average blood pressure.


Serious side effects:

  • Shortness of breath, even with mild exertion
  • Chest pain, feeling like you might pass out
  • Swelling in your ankles or feet
  • Pounding heartbeats or fluttering in your chest
  • Tremors, restlessness, trouble sleeping
  • Unusual changes in mood or behavior
  • Increased blood pressure (severe headache, blurred vision, pounding in your neck or ears, anxiety, nosebleed)

Common side effects:

  • Itching
  • Dizziness
  • Headache
  • Dry mouth
  • Unpleasant taste
  • Diarrhea
  • Constipation
  • Stomach pain
  • Increased or decreased interest in sex

📔 Additional Note

For phentermine, a study showed the common side effects of phentermine include dry mouth and insomnia. These side effects were reported more frequently in the group taking phentermine compared to the placebo group. Still, they were not severe enough to prevent participants from continuing the study.

Other potential side effects include palpitation, tachycardia, elevated blood pressure, dizziness, mood changes, tremor, headache, unpleasant taste, diarrhea, urticaria, impotence, and changes in libido. However, the study suggests that these side effects were not reported as significantly problematic.


The costs of Contrave and Phentermine can vary significantly. We'll compare some pricing options for both medications.


Contrave is available through the CurAccess Program, and the monthly cost for patients is $99 with free shipping. However, if your insurance covers Contrave, your out-of-pocket cost may be lower.

Patients participating in federal programs such as Medicaid, Medicare Part D, and TRICARE are eligible for the program. Still, it is processed as if the participant is a cash-paying customer.

With the CONTRAVE Savings Coupon Card, those with insurance may pay as low as $20, and those without insurance or insurance that doesn't cover Contrave will pay no more than $199. The actual payment may depend on your pharmacy and your insurance coverage.


Phentermine is available as a generic medication and is generally much more affordable compared to brand versions like Adipex-P.

Using a GoodRx coupon, you can access even more significant savings. The lowest GoodRx price for Phentermine (generic) is as low as $8.79, representing substantial cost savings for consumers.

The cost of Phentermine without insurance starts at $9.72 for a quantity of 30, 37.5 mg tablets using an RxSaver coupon. The actual retail price of Phentermine, as well as its brand counterparts, can vary depending on the pharmacy and location.

It's important to note that generic medications are typically more affordable than brand-name versions, making Phentermine a cost-effective option for individuals seeking weight loss medications.

Final Thoughts

Contrave may be better for long-term weight loss while Phentermine seems preferable for rapid short-term weight loss. Phentermine can produce faster initial weight loss but has more potential side effects like increased blood pressure. Contrave has fewer acute side effects but is more expensive, especially without insurance.

The right medication should be selected based on desired length of use, existing medical conditions, and cost considerations. Consulting a doctor is important to determine which option is best suited on an individual basis.

FAQs on Contrave and Phentermine

Do any weight loss pills have better results than Contrave?

Qsymia is generally considered more effective than Contrave, and it's also associated with a lower incidence of people discontinuing its use due to side effects.

Can I take Contrave and Phentermine together?

Combining Contrave and phentermine is not recommended. Phentermine should not be used in conjunction with other weight loss medications. Examples of such medications include Alli (Orlistat) and Contrave (naltrexone/bupropion).

What is stronger than Phentermine?

Brontil is a more potent dietary medication compared to Phentermine. Both Brontil and Phendimetrazine contain a higher stimulant content, making them more likely to lead to drug dependence. Phendimetrazine should be used for short periods, while Phentermine can be taken for up to 3 months.

Is Contrave the same as Xenical?

Xenical and Contrave belong to different drug classes. Xenical is a gastrointestinal lipase inhibitor, while Contrave is a combination of an opioid antagonist and an antidepressant. Some similar side effects of both Xenical and Contrave include stomach/abdominal pain, nausea, vomiting, diarrhea, headache, and skin rash.

Is Contrave just an appetite suppressant?

Contrave functions by targeting the areas of the brain that regulate hunger and cravings. However, it's important to note that Contrave is not solely an appetite suppressant. It works through a different mechanism to address weight loss.

What are the contraindications for Contrave?

Contrave should not be used in individuals with uncontrolled hypertension. It is contraindicated for those with a seizure disorder or a history of seizures. The use of other bupropion-containing products is also a contraindication.

Illustration of a healthcare provider asking questions on a smart phone.
Virtual weight loss solution
A personalized GLP-1 medication program delivered to you via our partner Korb Health
Illustration of a healthcare provider asking questions on a smart phone.
  • Free consultation; program starts at $269/mo
  • Checkmark Inside Circle.Customized online program and wellness coaching
  • Prescription medications and supplies shipped to your door