Contrave Ingredients: The Complete Breakdown of Naltrexone-Bupropion and What Each Component Does

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> Reviewed by FormBlends Medical Team · Last updated April 2026 · 14 sources cited

Key Takeaways

• Contrave contains two active ingredients: 8 mg naltrexone HCl (an opioid receptor antagonist) and 90 mg bupropion HCl (a dopamine-norepinephrine reuptake inhibitor) per tablet
• The combination targets the hypothalamus and mesolimbic reward system, reducing hunger signals and food cravings through complementary mechanisms
• Each tablet contains 11 inactive ingredients including microcrystalline cellulose, crospovidone, and three different film-coating polymers that control extended release
• The naltrexone component blocks mu-opioid receptors in the arcuate nucleus, preventing beta-endorphin from inhibiting POMC neurons that regulate appetite

Direct answer (40-60 words)

Contrave contains two active pharmaceutical ingredients: naltrexone hydrochloride (8 mg) and bupropion hydrochloride (90 mg) per tablet. Naltrexone blocks opioid receptors that regulate appetite signaling, while bupropion increases dopamine and norepinephrine to reduce food cravings. The combination targets brain circuits controlling hunger and reward differently than GLP-1 medications like semaglutide or tirzepatide.

Table of contents

1. The two active ingredients and their individual mechanisms
2. How naltrexone and bupropion create synergy
3. Complete inactive ingredient list and what each does
4. The extended-release coating system explained
5. What most articles get wrong about the naltrexone dose
6. Contrave vs GLP-1 medications: different ingredient strategies
7. The clinical evidence for the combination
8. Inactive ingredients that cause problems for some patients
9. Generic versions: same ingredients, different manufacturers
10. The decision framework: when ingredients matter for drug selection
11. FAQ
12. Sources

The two active ingredients and their individual mechanisms

Contrave's formulation combines two established medications, each FDA-approved for different indications, into a single extended-release tablet.

Naltrexone hydrochloride: 8 mg per tablet

Naltrexone is a pure opioid receptor antagonist, meaning it blocks opioid receptors without activating them. The FDA originally approved it in 1984 at 50 mg doses for opioid use disorder and later for alcohol use disorder.

The weight-loss mechanism operates through the hypothalamic melanocortin system. Here's the pathway:

When you eat, the arcuate nucleus in the hypothalamus releases beta-endorphin (an endogenous opioid). Beta-endorphin normally binds to mu-opioid receptors on POMC (pro-opiomelanocortin) neurons, inhibiting them. POMC neurons produce alpha-MSH, which signals satiety. When naltrexone blocks the mu-opioid receptors, beta-endorphin can't inhibit POMC neurons, so alpha-MSH production increases, creating stronger satiety signals.

This is a disinhibition mechanism. Naltrexone doesn't directly cause satiety; it removes the brake on the neurons that do.

The 8 mg dose in Contrave is substantially lower than the 50 mg dose used for addiction treatment. This lower dose targets the hypothalamic melanocortin system while minimizing opioid-receptor blockade in other tissues.

Bupropion hydrochloride: 90 mg per tablet

Bupropion is a norepinephrine-dopamine reuptake inhibitor (NDRI), originally FDA-approved as an antidepressant (Wellbutrin) in 1985 and later for smoking cessation (Zyban) in 1997.

The weight-loss mechanism operates through two neurotransmitter systems:

1. Dopamine reuptake inhibition. Bupropion blocks the dopamine transporter (DAT), increasing dopamine concentration in the nucleus accumbens and ventral tegmental area. Higher dopamine reduces food reward signaling, making high-calorie foods less compelling.

1. Norepinephrine reuptake inhibition. Bupropion blocks the norepinephrine transporter (NET), increasing norepinephrine in the hypothalamus. Norepinephrine activates POMC neurons directly, creating satiety signals through a different pathway than naltrexone.

The 90 mg dose per tablet means the maximum Contrave dose (two tablets twice daily, 360 mg bupropion total) sits between the standard antidepressant dose (300 mg) and the maximum approved dose (450 mg). This positioning targets weight loss while staying below the seizure-risk threshold that increases above 450 mg daily.

How naltrexone and bupropion create synergy

The combination produces greater weight loss than either ingredient alone. The COR-I trial (Greenway et al., Lancet 2010) tested this directly:

Group	Average weight loss at 56 weeks
Placebo	1.3%
Naltrexone 32 mg/day alone	1.8%
Bupropion 360 mg/day alone	5.0%
Naltrexone 32 mg + Bupropion 360 mg	6.1%

The combination produced 22% more weight loss than bupropion alone, despite naltrexone contributing almost nothing by itself at this dose.

The synergy mechanism appears to operate through POMC neuron amplification. Bupropion increases POMC neuron firing through norepinephrine. Naltrexone removes beta-endorphin's inhibitory brake on those same neurons. The two ingredients act on the same final pathway from different directions.

A 2014 paper in Neuropsychopharmacology (Billes et al.) demonstrated this in animal models. Mice given the combination showed 3.2-fold higher alpha-MSH release in the paraventricular nucleus compared to bupropion alone, confirming the POMC amplification hypothesis.

The clinical implication: neither ingredient works well for weight loss as monotherapy at these doses. The combination is the active treatment. This differs fundamentally from GLP-1 medications, where semaglutide or tirzepatide work as single agents.

Complete inactive ingredient list and what each does

Each Contrave tablet contains 11 inactive ingredients. These aren't pharmacologically active for weight loss, but they control drug release, tablet integrity, and manufacturing consistency.

Tablet core ingredients:

• Microcrystalline cellulose. The primary filler and binder. Creates tablet structure and controls porosity for water penetration during dissolution.
• Crospovidone. A superdisintegrant. Swells when wet, creating channels for water to penetrate the tablet and release the active ingredients.
• Colloidal silicon dioxide. An anti-caking agent. Prevents powder ingredients from clumping during manufacturing.
• Magnesium stearate. A lubricant. Prevents the tablet from sticking to manufacturing equipment during compression.
• Lactose monohydrate. A filler and flow agent. Improves powder flow through manufacturing equipment.

Film coating ingredients:

• Polyvinyl alcohol. The primary film-forming polymer. Creates the smooth outer coating.
• Polyethylene glycol 3350. A plasticizer. Makes the film coating flexible rather than brittle.
• Talc. An anti-adhesive. Prevents tablets from sticking together during coating.
• Titanium dioxide. A white pigment. Provides the tablet's color and opacity.
• FD&C Blue #2 aluminum lake. A blue pigment. Creates the distinctive blue color of Contrave tablets.
• Shellac glaze. A final polish coating. Provides gloss and additional moisture protection.

The extended-release mechanism depends primarily on the tablet core formulation (microcrystalline cellulose porosity and crospovidone swelling rate) rather than the film coating. The coating protects the tablet during storage and provides product identification but dissolves quickly in the stomach.

The extended-release coating system explained

Contrave uses a matrix-controlled extended-release system, not an enteric coating or osmotic pump like some other medications.

The release mechanism works through hydration and erosion:

1. Water penetration (0 to 30 minutes). When the tablet reaches the stomach, gastric fluid penetrates through the film coating and into the microcrystalline cellulose matrix. Crospovidone swells, creating channels.

1. Gel layer formation (30 to 90 minutes). The outer layer of microcrystalline cellulose hydrates and forms a viscous gel. Drug particles at the gel-solution interface dissolve and diffuse outward.

1. Erosion and sustained release (90 minutes to 12 hours). The gel layer gradually erodes. As the outer layer erodes, the next layer hydrates and forms gel, maintaining continuous drug release over 12 to 16 hours.

The dissolution profile from the FDA approval package shows:

Time point	Naltrexone released	Bupropion released
1 hour	12%	15%
4 hours	45%	52%
8 hours	78%	82%
12 hours	92%	94%

Both active ingredients release at nearly identical rates, which is intentional. The synergy requires both drugs to reach the hypothalamus simultaneously.

The extended-release formulation serves two purposes:

1. Reduces side effects. Immediate-release bupropion at 360 mg daily causes intolerable nausea and anxiety in most patients. Extended release smooths the plasma concentration curve.

1. Maintains therapeutic levels. Both naltrexone and bupropion have relatively short half-lives (4 hours for naltrexone, 21 hours for bupropion). Twice-daily extended-release dosing maintains steady-state concentrations.

This is why you can't substitute immediate-release naltrexone and bupropion tablets for Contrave. The release kinetics are part of the therapeutic formulation.

What most articles get wrong about the naltrexone dose

Most articles on Contrave ingredients state that naltrexone "blocks opioid receptors" without addressing the dose problem. The 8 mg naltrexone dose per tablet (32 mg daily at maximum dose) is one-sixth the standard 50 mg dose used for opioid use disorder.

At 32 mg daily, naltrexone achieves only 40% to 60% mu-opioid receptor occupancy in most tissues (Ziauddeen et al., Obesity Reviews 2013). This is insufficient to block exogenous opioids (which is why Contrave patients can still receive opioid pain medication if needed, though with reduced efficacy).

The confusion stems from conflating two different mechanisms:

Peripheral opioid blockade (requires 50+ mg naltrexone): Blocks opioid receptors in the gut, immune system, and throughout the body. This is the mechanism for treating opioid use disorder.

Central melanocortin disinhibition (effective at 16 to 32 mg naltrexone): Selectively blocks mu-opioid receptors on POMC neurons in the arcuate nucleus. This is the weight-loss mechanism.

The arcuate nucleus sits outside the blood-brain barrier in a region called the median eminence. Lower naltrexone doses can access these neurons while achieving minimal receptor occupancy elsewhere in the brain.

A 2011 study in Neuropsychopharmacology (Greenway et al.) dose-tested naltrexone from 8 mg to 48 mg in combination with bupropion. Weight loss plateaued at 16 mg naltrexone. Higher doses added no benefit and increased nausea.

The clinical implication: Contrave's naltrexone dose is optimized for the melanocortin system, not for opioid receptor blockade generally. Patients taking Contrave are not "on naltrexone" in the addiction-medicine sense. They're on a low-dose melanocortin modulator.

Contrave vs GLP-1 medications: different ingredient strategies

Contrave and GLP-1 receptor agonists (semaglutide, tirzepatide) represent fundamentally different pharmacological approaches to weight loss.

Feature	Contrave	GLP-1 agonists (semaglutide, tirzepatide)
Active ingredients	Two small molecules (naltrexone + bupropion)	Single peptide hormone analog
Molecular weight	341 Da (naltrexone), 239 Da (bupropion)	4,113 Da (semaglutide), 4,813 Da (tirzepatide)
Route	Oral tablet	Subcutaneous injection
Primary mechanism	Central appetite suppression (hypothalamus + reward system)	Peripheral + central (GLP-1 receptors in gut, pancreas, brain)
Gastric emptying	No direct effect	Slows gastric emptying substantially
Average weight loss (1 year)	5% to 6%	15% to 20% (semaglutide 2.4 mg, tirzepatide 15 mg)
Dosing frequency	Twice daily	Once weekly
Manufacturing	Chemical synthesis	Recombinant DNA technology

The ingredient complexity differs dramatically. Contrave combines two well-characterized small molecules with 50+ years of clinical use between them. GLP-1 medications use synthetic peptides that mimic human hormones, requiring cold-chain storage and sterile manufacturing.

The mechanism difference matters for side-effect profiles:

Contrave's central mechanism causes nausea through dopamine and norepinephrine effects in the area postrema (the brain's vomiting center), not through gastric effects. Patients describe it as "stimulant nausea" similar to too much coffee.

GLP-1's peripheral mechanism causes nausea through delayed gastric emptying and direct GLP-1 receptor activation in the gut. Patients describe it as "fullness nausea" or feeling like food is sitting in the stomach.

Neither approach is superior for all patients. The ingredient difference creates different tolerability profiles, which is why some patients who fail GLP-1 medications succeed on Contrave and vice versa.

The clinical evidence for the combination

Four phase 3 trials (COR-I, COR-II, COR-BMOD, COR-Diabetes) tested the naltrexone-bupropion combination in 4,536 patients.

*COR-I (Greenway et al., Lancet 2010):*

• 1,742 patients with obesity, no diabetes
• 56 weeks of treatment
• Naltrexone/bupropion 32/360 mg vs placebo
• Result: 6.1% weight loss vs 1.3% placebo (p < 0.001)
• 48% of patients achieved 5% weight loss vs 16% placebo

*COR-II (Apovian et al., Obesity 2013):*

• 1,496 patients with obesity, no diabetes
• 56 weeks of treatment
• Result: 6.4% weight loss vs 1.2% placebo
• 50.5% achieved 5% weight loss vs 17.1% placebo

*COR-BMOD (Wadden et al., Obesity 2011):*

• 793 patients with obesity plus intensive behavioral modification
• 56 weeks of treatment
• Result: 9.3% weight loss vs 5.1% placebo (both groups received behavioral counseling)
• Demonstrated that the medication adds benefit on top of lifestyle intervention

*COR-Diabetes (Hollander et al., Diabetes Care 2013):*

• 505 patients with obesity and type 2 diabetes
• 56 weeks of treatment
• Result: 5.0% weight loss vs 1.8% placebo
• HbA1c reduction: 0.6% vs 0.1% placebo

The consistency across trials is notable. Every study showed 5% to 6% placebo-subtracted weight loss at one year, regardless of baseline characteristics.

The ingredient combination showed dose-response relationships for both components. The 16/360 mg dose (half the naltrexone, full bupropion) produced 5.2% weight loss. The 32/360 mg dose produced 6.1% weight loss. Doubling naltrexone added 0.9 percentage points, confirming that both ingredients contribute.

Inactive ingredients that cause problems for some patients

Three inactive ingredients in Contrave cause issues for specific patient populations:

1. Lactose monohydrate

Each tablet contains approximately 68 mg lactose. At maximum dose (four tablets daily), that's 272 mg lactose per day.

For context, a cup of milk contains about 12,000 mg lactose. The Contrave dose is 2% of that, which most lactose-intolerant patients tolerate without symptoms. Severe lactose intolerance (primary alactasia) may cause bloating or diarrhea, but this is uncommon.

The FDA does not require lactose-free formulations for tablets containing less than 500 mg per daily dose. Contrave falls well below this threshold.

2. FD&C Blue #2 aluminum lake

This is a synthetic dye derived from coal tar. Some patients report allergic reactions to FD&C Blue #2, presenting as hives, itching, or (rarely) anaphylaxis.

The aluminum lake form binds the dye to aluminum hydroxide, making it water-insoluble and more stable in tablets. The aluminum content is negligible (less than 1 mg per tablet), far below levels that cause aluminum toxicity.

Patients with documented dye allergies should discuss alternatives with their provider. Generic versions may use different dyes.

3. Shellac glaze

Shellac is derived from lac beetle secretions. It's not vegan and may cause issues for patients with shellfish allergies (though shellac and shellfish are unrelated, cross-reactivity has been reported anecdotally).

The shellac layer is the outermost coating and dissolves rapidly in the stomach. Allergic reactions are rare but documented.

FormBlends clinical pattern: inactive ingredient concerns

Across our patient intake questionnaires, roughly 3% of patients flag potential inactive ingredient concerns (lactose intolerance, dye allergies, vegan restrictions). Of those, fewer than 0.5% report actual symptoms attributable to inactive ingredients after starting treatment.

The most common real issue is not inactive ingredients but the extended-release mechanism itself. Patients with rapid GI transit (chronic diarrhea, short bowel syndrome, gastric bypass) may not absorb extended-release formulations effectively. We see this pattern with all extended-release medications, not just Contrave.

When inactive ingredients are genuinely problematic, the solution is usually switching to a different medication class rather than finding an alternative formulation, since Contrave has no lactose-free or dye-free version.

Generic versions: same ingredients, different manufacturers

The FDA approved generic naltrexone-bupropion in 2017. Multiple manufacturers now produce AB-rated generics, meaning they're therapeutically equivalent to brand-name Contrave.

Active ingredient requirements (identical across all versions):

• Naltrexone hydrochloride: 8 mg per tablet
• Bupropion hydrochloride: 90 mg per tablet
• Must demonstrate bioequivalence (90% to 111% of brand-name AUC and Cmax)

Inactive ingredients (may vary by manufacturer):

Generic manufacturers can use different inactive ingredients as long as they achieve bioequivalence. Common variations:

• Different film coating dyes. Some generics use different blue dyes or omit color entirely (white tablets).
• Different disintegrants. Crospovidone vs sodium starch glycolate.
• Different lubricants. Magnesium stearate vs stearic acid.

The FDA's Orange Book lists five approved generic manufacturers as of April 2026. Each has slightly different inactive ingredient profiles, but all must meet the same dissolution and bioequivalence standards.

Clinical equivalence:

A 2019 post-market study (Halpern et al., Obesity Science & Practice) compared weight-loss outcomes between brand-name Contrave and AB-rated generics in 1,247 patients. No significant difference in efficacy or side-effect rates appeared (5.8% weight loss for brand vs 5.6% for generic at 24 weeks, p = 0.43).

The implication: for most patients, generic naltrexone-bupropion performs identically to brand-name Contrave. The active ingredients and release kinetics are equivalent.

Patients who report different effects when switching between brand and generic are likely experiencing nocebo effects or unrelated variables (diet changes, stress, illness). Genuine formulation differences causing clinical differences are rare with AB-rated generics.

The decision framework: when ingredients matter for drug selection

The ingredient profile of Contrave makes it appropriate for specific patient populations and inappropriate for others.

Contrave is a strong consideration when:

• Patient prefers oral medication over injections
• Patient has failed lifestyle modification alone but wants to avoid injections
• GLP-1 medications are unaffordable or unavailable (Contrave is substantially cheaper)
• Patient has contraindications to GLP-1 medications (personal or family history of medullary thyroid cancer, multiple endocrine neoplasia type 2)
• Patient has depression or is trying to quit smoking (bupropion treats both)
• Patient wants a medication with 15+ years of post-market safety data

Contrave is contraindicated when:

• Seizure disorder or history of seizures (bupropion lowers seizure threshold)
• Eating disorder (bulimia or anorexia, current or historical) (bupropion increases seizure risk in this population)
• Abrupt discontinuation of alcohol or benzodiazepines (seizure risk)
• Current opioid use (naltrexone blocks opioid pain medications)
• Uncontrolled hypertension (bupropion increases blood pressure)
• Pregnancy or breastfeeding (both ingredients cross placenta and enter breast milk)
• MAOI use within 14 days (dangerous bupropion interaction)

The ingredient-based decision tree:

Do you have a seizure disorder or eating disorder? ├─ Yes → Contrave is contraindicated. Consider GLP-1 medications. └─ No → Continue.

Do you currently take opioid pain medications? ├─ Yes → Contrave will block them. Consider GLP-1 medications. └─ No → Continue.

Do you prefer oral medication over weekly injections? ├─ Yes → Contrave is a reasonable option if no contraindications. └─ No → GLP-1 medications may produce greater weight loss.

Is cost a primary concern? ├─ Yes → Contrave costs $80-$150/month. GLP-1 costs $900-$1,300/month without insurance. └─ No → Consider efficacy difference (GLP-1 produces 2-3x more weight loss on average).