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Contrave vs Phentermine: Main Differences and Similarities

As obesity is affecting more people each year, different treatment options have become available to help with weight management. Contrave (naltrexone/bupropion) and phentermine are two medications that are used with a reduced-calorie diet and exercise regimen to aid in weight loss. Although both medications have similar effectiveness, they work in different ways.

Contrave

Contrave is the brand name for the combination of naltrexone and bupropion. Naltrexone is classified as an opioid antagonist while bupropion is considered an aminoketone antidepressant. It is prescribed for those with a starting body mass index (BMI) of 30 kg/m2 or at least 27 kg/m2 with another condition such as hypertension, diabetes, or high cholesterol.

Contrave is only available as a brand medication with a prescription. It is taken as an extended-release oral tablet with a strength of 8 mg/90 mg of naltrexone/bupropion. The dose is often increased gradually over several weeks starting from one tablet daily to two tablets twice daily by week four.

Phentermine

Phentermine (Phentermine details) is known by its brand name, Adipex-P. It works as a sympathomimetic with the central nervous system and appetite suppressive effects. Phentermine is also effective for treating obesity in those with a BMI of 30 kg/m2 or 27 kg/m2 with another weight-related comorbidity.

Phentermine is available as a generic oral tablet with a strength of 37.5 mg. It also comes as a 15 mg, 30 mg, or 37.5 mg oral capsule. Phentermine is often taken once daily in the morning depending on a doctor’s direction. It is not usually recommended to be taken for more than a few weeks.

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Contrave vs Phentermine Side by Side Comparison

Contrave and Phentermine are different medications with their own unique qualities. Their similarities and differences can be found in the comparison table below.

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Contrave Phentermine
Prescribed For
  • Obesity
  • Overweight with other risk factors (hypertension, diabetes, hyperlipidemia)
  • Obesity
  • Overweight with other risk factors (hypertension, diabetes, hyperlipidemia)
Drug Classification
  • Opioid antagonist/Aminoketone combination
  • Sympathomimetic
  • Anorectic
Manufacturer
  • Generic
Common Side Effects
  • Nausea
  • Constipation
  • Headache
  • Dizziness
  • Dry mouth
  • Vomiting
  • Insomnia
  • Diarrhea
  • Anxiety
  • Flushing
  • Fatigue
  • Increased blood pressure
  • Stomach ache
  • Sweating
  • Tremors
  • Irritability
  • Altered sense of taste
  • Palpitations
  • Dry mouth
  • Insomnia
  • Increased heart rate
  • Increased blood pressure
  • Heart palpitations
  • Flushing
  • Sweating
  • Constipation
  • Diarrhea
  • Nausea
  • Dizziness
  • Headache
  • Tremors
  • Agitation
  • Nervousness
  • Restlessness
  • Irritability
  • Increased urination
  • Altered libido
Is there a generic?
  • No generic currently available
  • Phentermine is the generic name.
Is it covered by insurance?
  • Varies according to your provider
  • Varies according to your provider
Dosage Forms
  • Oral tablet
  • Oral tablet
  • Oral capsule
Average Cash Price
  • $348 per 120 tablets
  • $40 per 30 tablets
SingleCare Discount Price
Drug Interactions
  • Monoamine oxidase inhibitors (selegiline, phenelzine, isocarboxazid, etc.)
  • Alcohol
  • Opioids
  • Antidepressants
  • Antipsychotics
  • Beta-blockers
  • Antiarrhythmics
  • Digoxin
  • CYP2B6 inhibitors (clopidogrel, ticlopidine, etc.)
  • CYP2B6 inducers (lopinavir, efavirenz, etc.)
  • Levodopa
  • Amantadine
  • Monoamine oxidase inhibitors (selegiline, phenelzine, isocarboxazid, etc.)
  • Alcohol
  • Insulin
  • Oral hypoglycemic medications (glyburide, glimepiride, sitagliptin, pioglitazone, acarbose, etc.)
  • Adrenergic neuron blocking drugs (reserpine, guanethidine, etc.)
Can I use while planning pregnancy, pregnant, or breastfeeding?
  • Contrave is in Pregnancy Category X and may cause fetal harm when administered to pregnant women. Contrave is not recommended in pregnant women.
  • Phentermine is in Pregnancy Category X and may cause fetal harm when administered to pregnant women. Phentermine is not recommended in pregnant women.

Summary

 

Contrave (naltrexone/bupropion) and phentermine are two medications that can help treat obesity. While Contrave is a combination of opioid antagonist and antidepressant, phentermine has more direct effects on the central nervous system as a sympathomimetic. Both drugs are only recommended with an appropriate diet and exercise regimen.

Contrave is approved for long-term use of four weeks or more. Phentermine, on the other hand, is generally recommended for short-term use of a few weeks. Contrave is often taken more than once a day while phentermine is usually taken once daily in the morning.

Contrave has been shown to improve weight loss as well as triglyceride and cholesterol levels. Because bupropion is often used as an antidepressant, it can also help those with obesity and depression. Notable side effects of the drug include nausea and constipation.

Phentermine can help improve weight loss although it may produce some unwanted side effects such as high blood pressure and dry mouth. Therefore, it may not be preferred in people with heart-related conditions.

Both medications should only be used after a proper evaluation by a doctor. Due to their possible side effects and drug interactions, it is important to review overall medical history to determine which medication may be more appropriate.