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  • Tim Reed

Contrave & Weight Loss. Side Effects of Naltrexone/Bupropion

Updated: Apr 22

In this blog post, we will explore Contrave or Naltrexone as it is also known. We will cover the following:

As usual, clicking or tapping on the blue links above will take you to the relevant section.

A packet of contrave weight loss drugs
Contrave is a prescription drug for weight loss

What is Contrave?

Combating Weight Loss with Contrave and Naltrexone: A Comprehensive Guide

In the ongoing battle against obesity, the quest for effective weight loss strategies remains a top priority. Among the various approaches, pharmacological interventions have gained significant traction, offering a potential solution to supplement traditional methods like diet and exercise. Contrave, a combination of bupropion and naltrexone, has emerged as a promising contender in this realm.

Contrave is a prescription medication available as an oral extended-release tablet, designed to gradually release its active ingredients over a sustained period. Each tablet contains a fixed-dose combination of 8 milligrams (mg) of naltrexone and 90 mg of bupropion.

Understanding Contrave: A Synergistic Duo

Contrave, a prescription medication, harnesses the combined power of two established drugs: bupropion and naltrexone. Bupropion, an antidepressant, is believed to act on dopamine and norepinephrine neurotransmitters, potentially influencing appetite regulation and energy balance. Naltrexone, an opioid antagonist, is known to block the effects of opioids and endorphins, potentially modulating appetite control.

Mechanism of Action: Unveiling the Science

The exact mechanism by which Contrave promotes weight loss remains under investigation. However, several hypotheses have been proposed:

  1. Appetite Suppression: Bupropion may reduce appetite by increasing dopamine and norepinephrine levels in the brain, leading to a feeling of fullness.

  2. Reduced Cravings: Naltrexone may block the rewarding effects of food, potentially diminishing cravings and emotional eating behaviors.

  3. Energy Metabolism: Bupropion may enhance energy expenditure, potentially increasing calorie burn and promoting weight loss.

Efficacy: Unveiling the Clinical Evidence

Numerous clinical studies have evaluated the efficacy of Contrave in weight management. These studies have consistently demonstrated that Contrave, in conjunction with diet and exercise, can lead to significant and sustained weight loss compared to placebo.

Side Effects: A Balanced Perspective (we will come into more serious side effects later in this article).

Like all medications, Contrave carries the potential for side effects, which are typically mild and short-lived. These may include:

  1. Gastrointestinal: Nausea, vomiting, constipation, and dry mouth are the most common side effects.

  2. Central Nervous System: Headache, dizziness, insomnia, and anxiety may occur.

  3. Others: Increased sweating, dry skin, and changes in taste may also be experienced.

If there are more serious side effects or adverse effects, see medical help immediately.

Dosage: Striking the Right Balance

Contrave is typically initiated at a low dose and gradually increased over time to minimise side effects. The standard dosage is one 2-tablet combination twice daily, taken with food. For a missed dose, don't worry too much and carry on with your next dose following day.

Contraindications: Identifying Limitations

Contrave is not suitable for everyone. Individuals with certain medical conditions, such as seizures, uncontrolled hypertension, or liver or kidney disease, should consult their healthcare provider before considering Contrave.

Conclusion: A Promising Option in the Weight Loss Arsenal

Contrave, with its unique combination of bupropion and naltrexone, has emerged as a promising weight loss medication, demonstrating efficacy in clinical trials. While side effects may occur, they are generally mild and manageable. For individuals seeking pharmaceutical assistance in their weight loss journey, Contrave, under the guidance of a healthcare professional, may offer a valuable tool to supplement diet and physical activity.

What is the difference between Contrave and Naltrexone?

Naltrexone, a medication primarily used to treat alcohol and opioid dependence, has gained attention for its potential to aid individuals on their journey to recovery. However, like any pharmaceutical intervention, it comes with a set of potential side effects that require careful consideration.

Naltrexone belongs to a class of drugs known as opioid receptor antagonists. It works by blocking the effects of opioids, both natural and synthetic, by binding to the opioid receptors in the brain. This mechanism is thought to reduce the rewarding effects of substances like alcohol and opioids, making it a valuable tool in addiction treatment.

How Naltrexone works for Weight Loss?

Naltrexone on its own is not suitable for people wanting to reduce their body mass index and lose weight. Contrave contains the active ingredient naltrexone hydrochloride and pairs this with bupropion hydrochloride.

When Naltrexone is used in conjunction with Bupropion, you have a formula that works for weight loss. The combination of Naltrexone and Bupropion (which is Contrave) represents a promising avenue in the realm of weight management. By harnessing the synergistic effects of these two medications, healthcare professionals have a tool that addresses both the psychological and physiological aspects of obesity. However, it's crucial to note that individual responses to medications vary, and the decision to pursue this combination should be made under the guidance of a healthcare provider. Ongoing research continues to unravel the intricacies of how Naltrexone and Bupropion work together, offering hope for more effective and personalised approaches to combating obesity.

Naltrexone and Bupropion are distinct medications with different primary purposes. Naltrexone, an opioid receptor antagonist, is commonly used to treat alcohol and opioid dependence. On the other hand, Bupropion is an atypical antidepressant that has also been utilised for smoking cessation. However, when these two medications are combined, a remarkable synergy emerges, creating a potent tool for weight management.

Synergistic Mechanisms:

  1. Appetite Regulation:

    • Naltrexone's Role: Naltrexone's action on opioid receptors in the brain helps regulate the reward system associated with food consumption. By blunting the pleasurable sensations linked to eating, it may reduce the overall desire for food.

    • Bupropion's Role: Bupropion, primarily known for its effects on neurotransmitters like dopamine and norepinephrine, can influence appetite regulation. It may help control cravings and emotional eating by modulating these neurotransmitter systems.

    • Synergy: Together, Naltrexone and Bupropion create a synergistic effect, addressing both the reward-driven aspects of eating and the emotional triggers that contribute to overconsumption.

  1. Energy Expenditure:

    • Bupropion's Role: Bupropion is believed to increase energy expenditure, making it a unique contributor to weight loss. This effect can be particularly beneficial for individuals with obesity who may struggle with a sluggish metabolism.

    • Synergy: When combined with Naltrexone, Bupropion's impact on energy expenditure complements the appetite-regulating effects of Naltrexone, creating a more comprehensive approach to weight management.

  1. Metabolic Effects:

    • Naltrexone's Role: Naltrexone may have positive effects on insulin sensitivity and glucose metabolism, potentially addressing underlying metabolic issues associated with obesity.

    • Bupropion's Role: Bupropion has been associated with modest improvements in metabolic parameters, further contributing to its role in weight management.

    • Synergy: The combination of Naltrexone and Bupropion may offer a holistic approach, addressing not only behavioural aspects but also underlying metabolic factors that contribute to weight gain.

What are the side effects of Contrave?

Contrave's efficacy lies in its combination of two distinct medications – Naltrexone, an opioid receptor antagonist, and Bupropion, an atypical antidepressant. The synergistic action of these components is believed to influence appetite, energy expenditure, and metabolic processes, making it a valuable tool in the fight against obesity. As good as this sounds, there are reports of side effects. The risk of side effects is very real and you should seriously consider if Contrave is right for you if you have a medical condition.

Common Side Effects:

Nausea and Vomiting:

  • A frequent but generally mild side effect, nausea and, in some cases, vomiting may occur, particularly during the initial phase of treatment.


  • Headaches are commonly reported, often as a transient side effect. Adequate hydration and gradual titration of the medication can help alleviate this symptom.


  • Some individuals may experience difficulty falling asleep or staying asleep, which may be attributed to Bupropion's stimulating effects. Taking the medication earlier in the day can mitigate this side effect.


  • Dizziness, especially upon standing up quickly, can occur. It is recommended to rise slowly from a sitting or lying position to minimise this side effect. If you notice a change in heart rate with dizziness, get medical assistance immediately. (There have been concerns about an increased risk of heart attack).

Serious Side Effects:

While many individuals tolerate Contrave well, there are serious side effects that necessitate immediate medical attention. These include:

Suicidal Thoughts or Behaviours:

  • Bupropion, one of the components of Contrave, has been associated with an increased risk of suicidal thoughts, particularly in individuals with a history of depression. Monitoring for changes in mood and seeking prompt medical attention is crucial.

Allergic Reactions:

  • In rare cases, individuals may experience allergic reactions such as rash, itching, swelling, severe dizziness, or difficulty breathing. Any signs of an allergic reaction warrant immediate medical attention.


  • Bupropion has been linked to an increased risk of seizures. Individuals with a history of seizures or conditions that lower the seizure threshold should exercise caution, and any occurrence of seizures should be reported to a healthcare provider.

Liver Damage:

  • Both Naltrexone and Bupropion can affect liver function, and severe liver damage is a rare but serious side effect. Regular monitoring of liver function is essential during Contrave treatment.

Contrave offers a multifaceted approach to weight management, but it's crucial for individuals to be aware of potential side effects, ranging from mild to serious (it is advised to seek medical advice if you have high cholesterol or bipolar disorder - always speak with your healthcare provider). Open communication with healthcare providers is paramount, especially if any concerning symptoms arise. While Contrave may be a valuable tool for some individuals on their weight loss journey, careful monitoring and adherence to medical guidance are essential to ensure the benefits outweigh the risks.

How does it work?

Bupropion: A Modulator of Appetite and Energy Balance

Bupropion, an antidepressant with a long-standing history in medicine, plays a pivotal role in Contrave's weight loss effects. Its mechanism of action is thought to involve modulation of the dopamine and norepinephrine neurotransmitter systems, key players in appetite regulation and energy expenditure.

Dopamine, often dubbed the "feel-good" neurotransmitter, contributes to feelings of pleasure and reward. Elevated dopamine levels are associated with reduced appetite, as the brain signals satiety and diminishes the desire to consume food. Bupropion's ability to increase dopamine levels may thus contribute to appetite suppression and reduced food intake.

Norepinephrine, another crucial neurotransmitter, plays a role in energy metabolism and thermogenesis, the process of heat generation in the body. Bupropion's potential to enhance norepinephrine activity may lead to increased calorie burning and promote weight loss.

Naltrexone: Taming Cravings and Emotional Eating

Naltrexone, an opioid antagonist, contributes to Contrave's weight loss effects by targeting the brain's opioid system. Opioids, natural chemicals produced by the body, are known to induce feelings of pleasure and satisfaction. Naltrexone blocks the effects of these opioids, potentially diminishing cravings and emotional eating behaviors.

When individuals engage in emotional eating, the opioid system is activated, leading to the release of endorphins, the body's natural painkillers. These endorphins contribute to feelings of pleasure and reward, reinforcing the emotional eating cycle. Naltrexone's ability to block endorphin activity may help break this cycle, reducing the tendency to overeat in response to emotions. Monoamine oxidase inhibitors simply put are are medications used to manage and treat depression, among other neurological and psychiatric illnesses.

Synergy in Action: The Combined Impact of Bupropion and Naltrexone

The combination of bupropion and naltrexone in Contrave is thought to create a synergistic effect, amplifying the weight loss benefits of each individual component. Bupropion's modulation of appetite and energy balance complements naltrexone's ability to reduce cravings and emotional eating, creating a comprehensive approach to weight management.

Unraveling the Mysteries: Ongoing Research and Future Directions

While the scientific understanding of Contrave's mechanism of action has advanced significantly, there remains much to uncover. Ongoing research is delving deeper into the intricate interactions between bupropion, naltrexone, and various neurotransmitter systems, aiming to refine our understanding of how Contrave promotes weight loss. As research progresses, we may gain insights into optimising Contrave's efficacy and tailoring its use to specific patient populations. Additionally, exploring potential long-term effects and identifying biomarkers for treatment response are important avenues for future research.

It is also worth noting that Contrave works best as part of an overall weight management plan. Prescription drugs can often be highly effective, but they should be used in conjunction with a reduced-calorie diet and physical exercise.

Where can I get Contrave?

Contrave is only available with a doctor's prescription. Therefore, you must make an appointment and discuss the use of Contrave with your GP. This medicine is not for everyone. You cannot take it if you are pregnant (or trying to get pregnant) or if you are breastfeeding. People with heart disease, an eating disorder or mental illnesses are advised to carefully consider if Contrave tablets is the right road you should take to achieve your ideal weight. There are other weight loss drugs out there that work well and do not require a prescription.

​Further information


Contrave is not recommended for pregnant women or those intending to become pregnant. Consult your healthcare provider if you have any underlying medical conditions, are taking other medications, or are breastfeeding or considering breastfeeding. It is not a good idea to get anything unnatural in breast milk as this can carry significant risks for your little one. How to store Contrave?

Key Storage Principles:

  1. Cool and Dry Environment: Store Contrave in a cool, dry place away from excessive heat and moisture. Extreme temperatures can alter the stability of the medication's components. Avoid storing Contrave in the bathroom or near sources of heat, such as stoves or radiators. It is safe to store it at room temperature.

  2. Original Packaging: Keep Contrave in its original blister packaging until the time of administration. The blister packaging protects the tablets from moisture, dust, and light exposure.

  3. Out of Reach of Children and Pets: Store Contrave out of reach and sight of children and pets. Accidental ingestion can lead to serious consequences.

  4. Discard Unused Tablets: Dispose of any unused Contrave tablets properly. Follow local guidelines for medication disposal to prevent environmental contamination.

  5. Temperature Sensitivity: Contrave is not sensitive to freezing temperatures. However, it is essential to keep it away from extreme heat and humidity.

  6. Expiration Date: Do not use Contrave after the expiration date indicated on the packaging. Expired medication may lose its effectiveness and could pose safety risks.

  7. Travel Considerations: When traveling, store Contrave in a cool, dry place within your luggage. Avoid exposing it to excessive heat or moisture during transit.

Additional Tips:

  • Do not remove the tablets from the blister pack until you are ready to take them.

  • If you accidentally expose Contrave to excessive heat or moisture, consult your healthcare provider for guidance.

  • Store Contrave in a designated medication storage area away from other household items.

  • Regularly check your medication supply to ensure you have enough Contrave for the upcoming period.

Proper storage of Contrave ensures that you are receiving the intended dosage and therapeutic effects. By following these guidelines, you can maintain the medication's efficacy and minimise the risk of adverse reactions.

Other side effects and risk factors:

It is possible that you may have trouble sleeping during the first week or so or using Contrave. If you have panic attacks or suicidal ideation, it is vital that you get medical assistance immediately. The same goes for chest pain - if you have any concerns whatsoever or notice any unusual changes after taking Contrave, seek medical assistance with the highest priority.

Liver Disease and Liver Problems: Hepatic Concerns with Contrave: Naltrexone's Impact on Liver Health

Contrave has been associated with potential liver issues, including hepatitis, as indicated in clinical trials. Indications of liver problems encompass persistent abdominal pain, prolonged dark urine, yellowing of the eyes' whites, and fatigue. Should any of these symptoms manifest, it is imperative to promptly consult your healthcare professional.

Individuals with pre-existing liver conditions and a medical history of liver-related issues may receive a reduced Contrave dosage under their doctor's guidance. In cases of severe liver complications, discontinuation of Contrave may be recommended by your healthcare provider.

Alternatives to Contrave

If you are concerned about any potential side effects using Contrave, there are other weight loss medications that are available without a prescription. Another common prescription medication is Saxenda but like Contrave, you'll need to visit your GP for a prescription.

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