At a glance
| Zepbound | Contrave | |
|---|---|---|
| Form | Weekly injection | Twice-daily tablet |
| How often | Once-weekly injection | Twice-daily oral tablet — no injection |
| Weight loss in trials | Up to 20.9% — SURMOUNT-1 (72 weeks) | Up to 9.3% — COR-BMOD (56 weeks) |
| FDA approved | 2023 | 2014 |
| Made by | Eli Lilly | Currax Pharmaceuticals |
| How it works | A single molecule that activates two hunger-regulating signals in the brain — GIP and GLP-1 (both natural hormones released after eating). | Bupropion activates appetite-suppressing nerve cells in the brain's hunger control centre (the hypothalamus). |
| Monthly cost, self-pay | $299–$1,086/mowith the manufacturer savings programme; list ~$1,086 | $100–$400/mo |
| Most reported reaction | Nausea 31% (SURMOUNT-1) | Nausea 33% (COR-I) |
Every figure in this table is read from the same trial and label records used everywhere else on this site.
Weight loss in each drug's main trial
No head-to-head trial has compared these two drugs.
SURMOUNT-1 (72 weeks)
COR-BMOD (56 weeks)
In clinical trials, participants taking tirzepatide lost on average up to 20.9% of their starting body weight, and participants taking naltrexone / bupropion ER lost on average up to 9.3%. Those numbers come from two different studies: SURMOUNT-1 enrolled 2,539 adults with obesity or overweight with comorbidities, no type 2 diabetes over 72 weeks against placebo, while COR-BMOD enrolled adults with obesity, with intensive behaviour therapy over 56 weeks against placebo + intensive behaviour therapy. Who took part, how long each trial ran and what each drug was measured against all move the percentage, so the two figures are not a measured difference between the drugs.
Monthly cost, self-pay
The bar spans the range in each drug's price record — lowest listed price to highest.
with the manufacturer savings programme; list ~$1,086
Self-pay vials via LillyDirect from $299/month (2.5 mg) to $699/month (10–15 mg), per zepbound.lilly.com on 4 September 2026; list price ~$1,086/month; $25/month copay card for eligible commercial insurance.
~$100–$400/month (brand). Generic available in some markets.
Self-pay prices are what the manufacturer or the pharmacy lists, not what most people end up paying. Zepbound: $299–$1,086/month. Contrave: $100–$400/month. Insurance, dose and pharmacy all change both figures.
Side effects reported in the trials
Both trials reported 3 reactions in common. Each rate is the percentage of participants who reported it in the trial named beside it, so the two columns are not from the same study.
A rate is the share of trial participants who reported that reaction, not a prediction for any one person.
How they differ in practice
How you take it
- Zepbound — Once-weekly subcutaneous injection (2.5, 5, 7.5, 10, 12.5, 15 mg)
- Contrave — Oral extended-release tablet, twice daily
Dose build-up
- Contrave — titrated to 32/360 mg/day over 4 weeks
Where a drug is not listed here, its prescribing information sets out its own dose steps.
How soon it acts
- Zepbound — Noticeable appetite reduction typically within 4–8 weeks; significant weight loss by 12–16 weeks
- Contrave — Appetite and craving changes typically within 4–8 weeks; significant weight loss by 16–24 weeks
Heart and metabolic findings
- Zepbound — Improvements in systolic/diastolic blood pressure, triglycerides, LDL, and HbA1c across SURMOUNT trials.
- Contrave — The LIGHT cardiovascular outcomes trial was terminated early due to a protocol violation and did not provide a definitive answer on CV outcomes.
As stated in each drug’s trial record — not a claim about which drug protects the heart more.
Other findings recorded
- Zepbound — Reduced progression to type 2 diabetes; improved sleep apnoea (SURMOUNT-OSA trial)
- Contrave — May help specifically with emotional eating and food cravings; bupropion's antidepressant effect may be beneficial if low mood contributes to overeating
If you stop taking it
- Zepbound — In SURMOUNT-4, participants who switched to placebo regained an average of 14.0% body weight over 52 weeks.
- Contrave — Weight regain after stopping is expected.
Common questions
Written and maintained by one person · Built with agentic AI tools · Every number checked against the cited trial · Not medical advice
Clinical evidence — Tirzepatide and Naltrexone / Bupropion ER
No head-to-head trial has compared these two drugs.
- SURMOUNT-1 — Tirzepatide: 2,539 adults with obesity or overweight with comorbidities, no type 2 diabetes, 72 weeks. New England Journal of Medicine, 2022. View source ↗
- COR-BMOD — Naltrexone / Bupropion: Adults with obesity, with intensive behaviour therapy, 56 weeks. Obesity, 2011. View source ↗
- COR-I — Naltrexone / Bupropion: 1,742 adults with obesity or overweight with comorbidities, 56 weeks. The Lancet, 2010. View source ↗
- Zepbound (tirzepatide) — FDA prescribing information — DailyMed View source ↗
- Contrave (naltrexone and bupropion extended-release) — FDA prescribing information — DailyMed View source ↗
Next step most people take
Built with agentic AI tools and not a substitute for medical advice
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