Phentermine vs. Contrave

Are phentermine and Contrave the same kind of drug?

No — they are completely different medications. Phentermine is a single drug, a sympathomimetic amine that suppresses appetite much like a mild stimulant. Contrave is a fixed combination of two older drugs — naltrexone (used for addiction) and bupropion (an antidepressant) — that together reduce appetite and food cravings.

They share a goal (less hunger, less eating) but almost nothing else: different chemistry, different approved length of use, and different safety profiles [1], [2].

What is phentermine?

Phentermine is a short-term appetite suppressant — one of the oldest weight-loss drugs, FDA-approved since 1959 and sold generically and under brand names such as Adipex-P and Lomaira. It is a sympathomimetic amine that prompts the brain to release norepinephrine, which blunts hunger.

It is taken as a once-daily oral tablet or capsule and is FDA-approved only as a short-term (a few weeks) addition to diet and exercise for obesity [1]. Because the appetite-suppressing effect tends to fade as the body adjusts, and because it is a Schedule IV controlled substance with potential for dependence, the label does not support open-ended use [1].

What is Contrave?

Contrave is a combination tablet for long-term weight management. Each tablet pairs naltrexone (8 mg) with bupropion (90 mg) in an extended-release form, and the dose is titrated over four weeks up to two tablets twice daily.

It is FDA-approved as an addition to a reduced-calorie diet and exercise for adults with obesity (BMI ≥30), or overweight (BMI ≥27) plus a weight-related condition, and it is intended for ongoing use [2].

It is not a controlled substance, but because it contains bupropion — an antidepressant — it carries a boxed warning for suicidal thoughts and behaviors [2].

How they work

Phentermine works mainly by suppressing appetite through stimulant-like activity in the brain — it raises norepinephrine, which reduces hunger signals [1].

Contrave works on two brain systems at once: bupropion stimulates appetite-regulating neurons in the hypothalamus, while naltrexone blocks a feedback loop in the brain's reward pathway that otherwise limits bupropion's effect. Together they reduce both appetite and the cravings that drive eating [2].

In short, phentermine is a straightforward appetite brake, while Contrave also targets the reward and craving side of eating.

Short-term vs. long-term: the key difference

This is the distinction that matters most. Phentermine is FDA-approved only for short-term use — typically up to about 12 weeks — as a jump-start while you build diet and activity habits [1]. Contrave is approved for long-term, continuous use, with the expectation that obesity is a chronic condition needing ongoing treatment [2].

That single difference shapes who each drug is for: phentermine for a short, supervised boost; Contrave for sustained management. (Some clinicians do prescribe phentermine for longer under close supervision, but that is beyond its FDA labeling.)

Effectiveness: how much weight do they take off?

Contrave has the clearer long-term evidence. In its pivotal COR-I trial, adults on Contrave lost a mean −6.1% of body weight at 56 weeks versus −1.3% on placebo, and 48% lost at least 5% of their weight (versus 16% on placebo) [3].

Phentermine produces meaningful early weight loss too, but it is studied and used over weeks rather than a year, so the two are not measured on the same timescale. The practical takeaway: phentermine can deliver a quick early drop, while Contrave is built to produce and hold a moderate loss over the long term [1], [3].

Both are less powerful than the GLP-1 medications, which reach 15–20% in trials.

It's also worth knowing that phentermine's appetite effect can plateau as the body adapts — part of why it is meant for short stretches rather than continuous use — whereas Contrave's more modest but steadier effect is designed to be maintained over time [1], [2].

What to expect: starting and stopping

The two drugs are started and monitored differently. Phentermine is usually taken once daily as a short course — often around 12 weeks — while your clinician keeps an eye on your blood pressure and heart rate [1].

Contrave is titrated up slowly over the first four weeks to ease nausea, and its label advises a checkpoint at 16 weeks: if you haven't lost at least 5% of your body weight by then, it is unlikely to help and should be stopped [2].

With either drug, weight tends to return if the medication and the lifestyle changes behind it don't continue — which is why obesity is treated as an ongoing condition rather than a quick fix.

Side effects & safety

Phentermine's side effects are stimulant-like: increased heart rate and blood pressure, palpitations, restlessness, insomnia, dry mouth, and constipation [1].

Contrave's most common side effect is nausea (reported by about 30% in trials), along with constipation, headache, vomiting, dizziness, insomnia, and dry mouth; it can also raise blood pressure and heart rate, especially in the first months [2], [3].

Who should not take these (and key cautions)

Both require careful screening. Phentermine should be avoided with heart disease, uncontrolled high blood pressure, an overactive thyroid, glaucoma, agitation, a history of drug misuse, during or within 14 days of an MAOI antidepressant, and in pregnancy or breastfeeding [1].

Contrave is contraindicated with uncontrolled hypertension, any seizure disorder, eating disorders (bulimia or anorexia), chronic opioid use or opioid withdrawal, the abrupt stopping of alcohol or sedatives, MAOIs, and pregnancy — and its boxed warning means anyone taking it should be watched for mood changes or suicidal thoughts [2].

Tell your clinician your full history, including all medications, before starting either one.

Cost & coverage

Cost is one of phentermine's biggest advantages — as an old generic it is inexpensive, often only a few dollars to a few tens of dollars a month. Contrave is brand-name and costs considerably more, though manufacturer savings programs can lower the price for eligible patients [1], [2].

As with most weight-loss drugs, insurance coverage for obesity treatment is inconsistent, so what you actually pay depends on your plan. A supervised medical weight-loss program like JumpstartMD's can help you find the most cost-effective option for your situation.

A note on phentermine and Qsymia

Phentermine also lives inside another weight-loss drug — Qsymia, which combines phentermine with topiramate. That combination is FDA-approved for long-term use and produces more weight loss than phentermine alone.

So if you respond well to phentermine but need a longer-term, more powerful option, Qsymia keeps the phentermine component while adding a second mechanism — meaning the decision isn't strictly "short-term phentermine or long-term Contrave." It's a good option to raise with your clinician [1].

Which is right for you?

• You want a low-cost, short-term jump-start → phentermine is inexpensive and works quickly over a few weeks [1].
• You want ongoing, long-term treatment → Contrave is FDA-approved for continuous use and has one-year trial data [2], [3].
• You struggle with cravings or emotional eating → Contrave's effect on the reward pathway may be a better fit [2].
• You have heart disease or take an antidepressant → the safety details differ a lot between them, so this needs a clinician's review [1], [2].

The right choice depends on your goals, timeline, other conditions, and medications — exactly what a supervised consultation sorts out. JumpstartMD physicians prescribe and manage both phentermine and Contrave (as well as the newer GLP-1 options), matching the medication to your health and goals.