Contrave Side Effects: The Complete 2026 Guide

Contrave Side Effects: Overview

Contrave is an FDA-approved medication, but its side effect profile is notably more complex than most weight loss drugs. Because it combines two pharmacologically active compounds — bupropion (an antidepressant) and naltrexone (an opioid antagonist) — patients may experience adverse effects from either drug, plus effects that emerge from the combination.

In the pivotal Phase 3 trials, 23–26% of patients discontinued Contrave due to adverse events, compared to 12–14% on placebo. That's a notable dropout rate and gives a practical signal of how tolerable the medication really is.

Below, we break down side effects by frequency (common vs. serious), mechanism, and timing — and compare them to the alternative most patients should consider instead: GLP-1 medications.

Contrave Side Effects: First Week

The first week on Contrave involves only one pill per day (the beginning of the 4-week titration) — yet it is still when many patients experience the most pronounced side effects. Bupropion is responsible for most early reactions.

Typical first-week symptoms

• Nausea — most common first-week complaint, peaking on days 2–5
• Headache — often frontal, mild to moderate
• Insomnia — difficulty falling or staying asleep (bupropion is stimulating)
• Dry mouth
• Anxiety or jitteriness — particularly if sensitive to stimulants
• Dizziness on standing (orthostatic)

Do side effects of Contrave go away?

Most do. In clinical trials, the frequency of nausea, headache, and dizziness declined 40–60% between week 4 and week 12. Constipation and insomnia are the side effects most likely to persist at maintenance dose.

Common Side Effects of Contrave

From the FDA prescribing information and Phase 3 trial data, here are the adverse events that occurred in ≥5% of Contrave patients AND at least 1% more than placebo:

If you're comparing to GLP-1 medications: the types of side effects overlap significantly (nausea, constipation, vomiting). The difference is that Contrave adds CNS effects (insomnia, dizziness, anxiety, mood changes) that GLP-1s do not typically cause.

Serious Side Effects of Contrave

These are rare but clinically important. Seek immediate medical attention if any occur:

• Suicidal thoughts or behavior — especially in first 3 months
• Seizures — estimated 0.1% of patients at therapeutic dose
• Hypertension — bupropion can raise blood pressure
• Liver injury — naltrexone has rare hepatotoxicity (monitor LFTs)
• Angle-closure glaucoma
• Manic episodes (in bipolar-prone individuals)
• Hypersensitivity reactions — rash, urticaria, rare Stevens-Johnson
• Opioid overdose if patient uses opioids after naltrexone wears off (tolerance reset)

Contrave's Black Box Warning — Explained

The black box warning on Contrave is inherited from bupropion. It reflects pooled data from antidepressant trials showing a small but statistically significant increase in suicidal thinking among patients under 25.

What this means in practice:

• You should not start Contrave if you have active suicidal ideation
• Anyone with a history of bipolar disorder or major depression should be evaluated carefully
• Friends and family should know you've started a new medication and be asked to watch for behavioral changes
• You should schedule follow-up within 2–4 weeks of starting

Compared to GLP-1 medications, this is a major delta. Semaglutide, tirzepatide, and liraglutide do not carry suicidality warnings at their approved weight loss doses. (Note: a thyroid C-cell tumor warning applies to GLP-1s in rodents, but it has not been observed in humans at therapeutic doses.)

Contrave and Seizure Risk

Bupropion — and therefore Contrave — lowers the seizure threshold. The dose-dependent seizure rate for bupropion:

• 300 mg/day bupropion IR: ~0.1%
• 300–450 mg/day bupropion SR/XL: ~0.4%
• Contrave 360 mg/day bupropion: ~0.06–0.1% (extended-release formulation)

Contrave is contraindicated if you have:

• Seizure disorder (epilepsy)
• Eating disorder (anorexia, bulimia) — active or history
• Chronic opioid use (risk of withdrawal-induced seizure)
• Abrupt discontinuation of alcohol or benzodiazepines
• Use of other bupropion products (avoid double-dosing)

Seizure risk is also increased by: other medications that lower seizure threshold (tramadol, many antidepressants, quinolone antibiotics), head injury, CNS tumor, low blood sodium, and certain metabolic conditions.

Contrave and Alcohol — The Full Story

Avoiding alcohol on Contrave is one of the most consistent physician recommendations. There are three distinct concerns:

1. Seizure threshold

Heavy alcohol use or sudden alcohol withdrawal significantly lowers the seizure threshold. Stacking this with bupropion creates real risk.

2. Altered alcohol effects (naltrexone)

Naltrexone was developed specifically because it blocks the rewarding, euphoric effects of alcohol. Patients on Contrave frequently report that drinking "doesn't feel the same." Paradoxically, this can lead to drinking larger volumes to chase the usual effect — which increases toxicity without increasing perceived impairment.

3. Mood and sleep effects

Alcohol disrupts sleep architecture. Bupropion already causes insomnia in ~9% of patients. Alcohol worsens mood stability in patients on antidepressants.

Contrave Drug Interactions

Contrave has a long list of clinically significant interactions. High-priority interactions include:

Contraindicated

• Opioids (morphine, oxycodone, hydrocodone, codeine, tramadol, fentanyl) — naltrexone will block them; dangerous if high doses are used to overcome the block
• MAOIs (phenelzine, selegiline, linezolid) — must be stopped 14 days before starting Contrave
• Other bupropion products (Wellbutrin, Zyban, Aplenzin, Forfivo) — risk of seizure from double-dose
• Chronic opioid use or recent opioid withdrawal

Use with caution

• CYP2D6 substrates — bupropion is a strong 2D6 inhibitor; dose reductions may be needed for metoprolol, SSRIs, tricyclic antidepressants, tamoxifen, dextromethorphan
• Drugs that lower seizure threshold — tramadol, theophylline, systemic corticosteroids, quinolone antibiotics
• Antidiabetic medications — insulin and sulfonylureas may need dose reduction with weight loss
• Ritonavir, efavirenz, lopinavir — can decrease bupropion levels
• Warfarin — monitor INR more frequently

Who Should NOT Take Contrave

• Patients with uncontrolled hypertension
• Patients with seizure disorder
• Patients with bulimia or anorexia nervosa (current or past)
• Patients using chronic opioids, methadone, or buprenorphine
• Patients undergoing abrupt discontinuation of alcohol, benzodiazepines, barbiturates, or anti-seizure drugs
• Patients taking MAOIs (or within 14 days of stopping one)
• Patients with known hypersensitivity to bupropion or naltrexone
• Pregnant women — Contrave is not recommended in pregnancy
• Patients under 18 years of age

Side Effects of Stopping Contrave

Contrave does not produce classic withdrawal in the way that benzodiazepines or opioids do, but there are effects to expect when you stop:

• Appetite returns — usually within 3–7 days
• Weight regain — the pivotal trials showed significant weight regain by 6 months after stopping. This is true of virtually all anti-obesity medications (including GLP-1s), and reflects the chronic nature of obesity rather than "drug dependence"
• Mood effects — mild in most; more pronounced if Contrave was functionally treating depression
• Sleep normalizes — insomnia often improves within days
• Constipation resolves

Contrave can generally be stopped without a taper. However, if you have been on it for months and are taking high-dose concurrent medications, ask your prescriber.

Contrave Side Effects vs GLP-1 Side Effects

The honest comparison most patients care about:

Frequently Asked Questions