Contrave vs Phentermine: How to Choose the Right Weight Loss Drug

Contrave and Phentermine get compared constantly, even though they're more different than they are alike. Phentermine has been on the market since 1959, costs under $50 a month in generic form, and quickly suppresses appetite. Contrave is newer, combining two repurposed drugs in one pill meant for long-term use at roughly $843 a month without insurance. Here's how they stack up so you can talk through the right choice with a provider.

Key Takeaways

Phentermine suppresses appetite through stimulant activity and works within hours. It's FDA-approved for short-term use only, typically a few weeks at a time.
Contrave pairs naltrexone with bupropion to quiet cravings and reward circuits in the brain. It's designed for months of continuous use.
The cost gap is large: roughly $10–51 per month for generic phentermine versus about $843 per month for Contrave.
Phentermine is a Schedule IV controlled substance. Contrave is not, but it carries a black box warning for suicidal thoughts linked to bupropion.
The right pick depends on your medical history, how long you need pharmacological support, and what you can realistically afford.

Comparison Chart

	Contrave	Phentermine
Active ingredients	Naltrexone 8mg + bupropion 90mg	Phentermine HCl
Drug class	Opioid antagonist + aminoketone antidepressant	Sympathomimetic amine (CNS stimulant)
FDA approved	2014	1959
Controlled substance	No	Yes (Schedule IV)
Treatment duration	Long-term (trials up to 56 weeks)	Short-term (typically a few weeks)
Maintenance dose	2 tablets twice daily (32mg/360mg)	37.5mg once daily or 8mg three times daily
Avg weight loss in trials	17 lbs over 56 weeks; 42% lost ≥5%	Additional 7.9 lbs vs placebo; 45.6% lost ≥5% at 12 weeks
Cost without insurance	$843 for 120 tablets	$10–51 for 30 tablets (generic)
Generic available	No (expected in 2030)	Yes
Black box warning	Yes (suicidal thoughts)	No

What is Phentermine?

Long story short, Phentermine kills your appetite. It's a stimulant that pushes your brain to release norepinephrine, which dials down hunger signals. You take it in the morning and food just isn't on your mind the way it normally would be for most of the day.

It has been FDA-approved for nearly 70 years, making it among the oldest prescription weight loss drugs still prescribed today. While there's more hype behind Ozempic and Zepbound, millions of Phentermine prescriptions are filled every year.

You'll find two main formulations:

Adipex-P (37.5mg) is the standard, taken once daily before breakfast.
Lomaira (8mg) can be taken up to three times a day before meals, spreading the appetite suppression across the full day instead of concentrating it in the morning.

Generics come in 15mg and 30mg capsules, too.

Phentermine is only FDA-approved for short-term use because it's classified as a Schedule IV controlled substance. Some physicians prescribe it off-label in intermittent cycles, but that goes beyond the official indication and requires close monitoring.

The benefits of Phentermine are hard to ignore. You could feel it working within 24 hours of your first dose, as food cravings fade into the background and portion sizes shrink because you're simply not as hungry as you used to be.

What is Contrave?

Funny enough, neither of Contrave's two ingredients was built for weight loss. That just happens to be a side effect of combining them.

Bupropion was a commonly prescribed antidepressant (Wellbutrin). It was also used as a smoking cessation drug (Zyban).
Naltrexone was developed to block opioid receptors in recovering opioid addicts.

Researchers eventually discovered that combining them minimized appetite and cravings. Now it's one of the more sought-after weight loss solutions on the market, alongside the GLP-1 agonist drugs.

Each tablet packs 8mg of naltrexone and 90mg of bupropion in an extended-release formula. You'll ramp up to the full dose slowly over a few weeks. Most patients take one pill in the morning for the first week and are up to two pills twice a day by week four: 32mg naltrexone and 360mg bupropion total.

Titration is a key difference between the two drugs. Jumping straight to the maintenance dose would make the nausea, already the most common side effect, much worse. It's also why the results come on so much slower. You don't feel a dramatic appetite shift on day one the way you might with phentermine. Instead, you'll likely notice the volume on cravings turned down a few notches after a few weeks, and you don't have the same urge to eat once you feel full.

Contrave earned FDA approval in 2014. Unlike Phentermine, it's not a controlled substance. No generic version exists yet. One is coming, but we're still a few years out, and until it arrives you can expect to pay quite a bit more for Contrave than you would for Phentermine.

Both drugs can help you lose weight, but they're not prescribed in all the same scenarios. A lot of people find Contrave makes more sense when their weight problem is less about how much they eat and more about compulsive eating or reward-driven snacking.

Side-by-Side Comparison

The truth is, you probably aren't the one who has to decide between these drugs. Your prescribing doctor will look at your current bill of health, your goals, and your insurance, and figure out what makes the most sense. Still, here are the biggest differences and where the two drugs overlap and diverge.

Overlap in Use Case

First, what they have in common. Both medications target the same patient profile: adults with a BMI of 30 or higher, or 27 and above with at least one weight-related condition like type 2 diabetes, high cholesterol, or hypertension.

The FDA indication is nearly identical. Neither one is approved for cosmetic weight loss or for patients who just want to drop a few pounds. You need a qualifying medical condition to get a prescription for either drug. That's where the similarities end.

Accessibility and Cost

Cost is the biggest difference on paper. Generic phentermine costs about $51 for a 30-day supply at retail, and less than $10 with a discount coupon. Every pharmacy in the country stocks it.

Contrave, by contrast, averages $843 for a one-month supply at the maintenance dose. A lot of that is because only a brand-name drug is available. Insurance coverage can be hit or miss (mostly miss), and Medicare prescription plans generally don't cover it either.

Run the math on a 6-month course: roughly $60–300 total for phentermine versus $5,000+ for Contrave. It isn't a close call when insurance won't cover either drug, which is unfortunately common for weight loss drugs.

Dosage and Duration Differences

Phentermine is simple. Take 37.5mg once in the morning, or 8mg Lomaira three times a day before meals. Don't take it in the evening, or you'll end up lying awake until 3am.

Contrave's schedule takes four weeks to build:

Week 1: one tablet in the morning
Week 2: one morning, one evening
Week 3: two morning, one evening
Week 4 onward: two morning, two evening

Tablets must be swallowed whole. No splitting or crushing. Skip high-fat meals when you take it; fatty food increases drug absorption by up to 3.7 times and raises side effect risk. Patients on CYP2B6 inhibitors like ticlopidine or clopidogrel should not exceed one tablet twice daily.

Beyond dosage, there's a difference in duration. Phentermine is short-term, a few weeks at most. Some prescribers cycle patients on and off, but that's rare. Contrave was specifically made for long-term, ongoing support. Clinical trial patients stayed on it for up to 56 weeks, with a key caveat: prescribing guidelines say to discontinue if the scale hasn't moved at least 5% by week 12 at full dose.

Clinical Backing

No one has ever run a head-to-head trial comparing the two drugs, so keep that in mind. Every comparison pulls from separate studies with different designs and patient populations. That said, there's plenty of evidence on each drug in isolation.

Contrave's evidence comes from five placebo-controlled trials: 4,754 patients, up to 56 weeks. The study population was 82% female, 78% white, average age 46. 42% of Contrave patients lost at least 5% of their body weight, and average loss was about 17 pounds across the study period.

Phentermine's data is older, which makes sense since the drug has been around nearly 60 more years. A meta-analysis spanning studies of 2–24 weeks showed that patients lost around 8 pounds more than placebo. A 700-patient study in the Korean Journal of Family Medicine showed 45.6% hit the 5% body weight mark after 12 weeks.

Take all of this with a grain of salt. The timescales make a direct comparison misleading. You shouldn't compare 17 pounds over 56 weeks to 8 pounds over 2–24 weeks and draw a firm conclusion.

Possible Side Effects

Both drugs call for blood pressure and heart rate monitoring, as either can push those numbers higher.

One in three people on Contrave gets nauseous, 32.5% in clinical trials. That's the number that jumps off the page. The rest of the common side effect profile:

Constipation (19.2%)
Headache (17.6%)
Vomiting (10.7%)
Dizziness (9.9%)
Insomnia (9.2%)
Dry mouth (8.1%)
Diarrhea (7.1%)

The bigger concern is the black box warning. Bupropion is linked to suicidal thoughts and behavior in patients up to age 24. Seizures are rare but possible. Blood pressure can rise. Naltrexone blocks opioid receptors, so you'd have to wait at least 7–10 days if you need pain medication after taking Contrave, or you face a higher overdose risk.

Phentermine's side effects aren't as jarring, but they exist and align with what you'd expect from a stimulant. Insomnia (23%) is the most common. Dry mouth, elevated heart rate, restlessness, and headache are all possible as well. Some patients get palpitations or feel their heart racing in the first few days before the body adjusts. There's a slight risk of dependence, which is why it's a Schedule IV controlled substance, but there's little to worry about on that front if you follow your prescription closely.

Drug Interactions and Warnings

This is the kind of thing you'll talk through with your prescribing physician. Neither drug should be started within 14 days of stopping an MAOI. Both interact with diabetes medications, so blood sugar monitoring needs adjustment. Alcohol raises risk across the board.

Contrave has a longer list of interactions. It affects the CYP2D6 enzyme pathway and can quadruple metoprolol's blood concentration. It works through the same pathway as certain antipsychotics, SSRIs, tricyclic antidepressants, and heart rhythm drugs. Opioids are completely contraindicated because naltrexone blocks the receptors they need to work.

Phentermine shouldn't be combined with SSRIs, as it could cause serotonin syndrome. Pairing it with bupropion (half of Contrave) raises seizure risk. Phentermine is also contraindicated with cardiovascular disease, hyperthyroidism, glaucoma, and any history of drug abuse. This is exactly why the choice can't be made from a comparison chart alone. Your medication list and medical history determine which drug is safe for you.

Is Contrave Better Than Phentermine?

Not across the board. Contrave costs 10–80 times more and takes a full month before you even reach the effective dose, and the risk profile is more complex.

That said, Contrave does have real advantages for specific patients, like those who can't take a controlled substance or have a substance use history. It's also the more viable option for long-term support.

For most patients starting a weight loss medication conversation for the first time, Phentermine is the more practical starting point. It costs under $50 a month and has been around for over 65 years.

Either way, this decision isn't one to make alone. A licensed provider can review the full medical picture before prescribing anything, including medications you're already on, conditions that might rule one option out, and what a realistic treatment timeline looks like for your goals.

Tips on Taking Contrave or Phentermine

A few quick tips for getting started with weight loss drugs, no matter which one you land on:

Stick to the dosing schedule: Contrave's four-week ramp-up helps keep nausea at bay. Morning dosing is non-negotiable with phentermine to avoid sleep interactions.
Track your weight weekly: Your provider needs this data to determine if adjustments are necessary.
Skip alcohol: Contrave plus alcohol raises seizure risk. Phentermine plus alcohol amplifies everything from dizziness to impaired judgment. Staying sober will only improve your results anyway.
The medication supports a calorie deficit and exercise: Think of these drugs as tools rather than replacements. The more other tools you pair them with, the better.
Call your doctor right away if you notice chest pain, trouble breathing, severe mood changes, or thoughts of self-harm. Not the next day.

Most importantly, tell every provider and pharmacist you see about your weight loss prescription, including dentists and urgent care doctors. Drug interactions are documented with both medications, and your other prescribers need to know.

How to Get Started with Weight Loss Treatment at TMates

TMates connects you with a licensed provider who reviews your full medical picture, current medications, and goals before prescribing anything. If a medication makes sense for you, your prescription is fulfilled through a local pharmacy for a seamless process. Complete a short online intake to see what a realistic treatment plan could look like.

Frequently Asked Questions

Are Contrave and phentermine the same thing?

No. Contrave is naltrexone plus bupropion. Phentermine is a single-ingredient stimulant for short-term appetite suppression. They're entirely different drugs.

Is there phentermine in Contrave?

No. Contrave's two active ingredients are naltrexone (an opioid antagonist) and bupropion (an antidepressant).

Can you take Contrave and phentermine together?

Not recommended. Bupropion (in Contrave) plus phentermine raises seizure risk. Your physician picks one or the other based on your profile.

Are there alternatives to phentermine and Contrave?

Yes. Options like compounded semaglutide and tirzepatide are available through a telehealth evaluation with a licensed physician and a valid prescription. Qsymia, which combines phentermine with topiramate, is another option, as is orlistat (Alli/Xenical). Your doctor can help you narrow it down to the right one.

How much weight can I lose on these drugs?

There's no one-size-fits-all answer. Contrave trials showed an average of about 17 pounds over 56 weeks. Phentermine studies run over much shorter periods, since that's how the drug is meant to be used, and patients lost around 8 more pounds compared to placebo. Your diet, exercise, metabolism, and other factors all influence your results.

How fast will I start seeing results?

Phentermine works within hours. You'll likely feel your appetite quiet down on the first day, and weight typically starts moving within the first two weeks. Contrave takes longer, around four weeks, because of the titration schedule.

Will I gain weight back after stopping Contrave or phentermine?

Possibly. Neither drug permanently rewires your metabolism, and appetite returns to baseline when you stop. That's why the habits you build during treatment matter so much. The dietary patterns and exercise routines are what keep the weight off once the prescription ends.

Are these drugs safe during pregnancy?

No. Both are contraindicated. Weight loss during pregnancy can be detrimental to the fetus. Stop and contact your doctor immediately if you become pregnant while on either medication.

Can I drink alcohol while on Contrave or phentermine?

Avoid it with both. Contrave's label specifically warns about increased seizure risk when combined with alcohol. Phentermine plus alcohol worsens dizziness, raises heart rate, and impairs judgment.