Wellbutrin (bupropion) vs Prozac (fluoxetine)
Wellbutrin and Prozac, compared on what the public record actually supports: side effects by rate from each FDA label, what the largest trial comparison found, who takes each one, who pays, what the labels warn, and what the litigation record holds. Sources on every number.
the short answer
- is Wellbutrin or Prozac more effective? in the largest comparison of antidepressant trials (522 trials, 116,477 people, Lancet 2018), both beat placebo on response at about 8 weeks: bupropion odds ratio 1.58 (95% CrI 1.35 to 1.86), fluoxetine 1.52 (1.40 to 1.66). the authors called the differences between drugs mostly modest, with wide intervals.
- which has fewer side effects? the labels say their trials “cannot be directly compared”, because each drug was tested in different people under different rules. what each label prints: Wellbutrin (bupropion): 9% (300 mg/day); 11% (400 mg/day) stopped for an adverse reaction vs 4% on placebo (Wellbutrin XL label, SPL effective 2026-02-10). Prozac (fluoxetine): the label prints no discontinuation rate in the section we transcribed. the reactions both labels list, side by side, are in the table below. in the 2018 network, all-cause dropout against placebo was 0.96 for bupropion and 0.88 for fluoxetine.
- which should i take? not a question this page answers. the odds ratios are averages across thousands of strangers; your history, other medications and what you can live with are not in them. the questions for your prescriber below are built from what is on this page.
What this page will not do is rank them. These drugs are in different classes and were tested for partly different things, so a single-axis ranking would be a category error. Which one fits you turns on your history, your other medications, and side-effect trade-offs — a prescriber conversation. This page arms that conversation; here are the questions worth taking into it →
what the 522-trial comparison found for bupropion and fluoxetine
the 2018 Lancet network meta-analysis pooled 522 trials comprising 116 477 participants, the median duration of the acute treatment was 8 weeks (iqr 6–8), and compared 21 antidepressants against placebo and against each other on two outcomes: response (at least a 50% fall on the depression scale) and all-cause dropout, its stand-in for acceptability. odds ratios are against placebo. an odds ratio above 1 on response favours the drug; below 1 on dropout means fewer people stopped than on placebo.
| drug | response vs placebo, OR (95% CrI) | dropout vs placebo, OR (95% CrI) |
|---|---|---|
| Wellbutrin (bupropion) | 1.58 (1.35 to 1.86) | 0.96 (0.81 to 1.14) |
| Prozac (fluoxetine) | 1.52 (1.40 to 1.66) | 0.88 (0.80 to 0.96), fewer dropouts than placebo |
- bupropion: named in neither the more-effective nor the more-tolerable group of the head-to-head analysis.
- fluoxetine: among the least efficacious in head-to-head trials; among the more tolerable (fewer dropouts) in head-to-head trials.
the other direction, in the authors' words. “the certainty of evidence was moderate to very low”; “The random-effects summary SMD for all antidepressants was 0·30 (95% CrI 0·26–0·34)”, a modest average effect; “positive results need to be taken with great caution, because the trials in this network meta-analysis were of short duration”. 46 (9%) of 522 trials were rated as high risk of bias, 380 (73%) trials as moderate, and 96 (18%) as low. 409 (78%) of 522 studies were funded by pharmaceutical companies. the trials excluded people with psychotic, treatment-resistant or bipolar depression, and the paper says it cannot guide the next choice after a first drug fails. a difference between two odds ratios in the table above is not a difference between the drugs unless the direct comparison shows one.
Cipriani A, Furukawa TA, Salanti G, et al. Comparative efficacy and acceptability of 21 antidepressant drugs for the acute treatment of adults with major depressive disorder: a systematic review and network meta-analysis. Lancet 2018; doi:10.1016/S0140-6736(17)32802-7. funding of the analysis: National Institute for Health Research Oxford Health Biomedical Research Centre and the Japan Society for the Promotion of Science. The funder of this study had no role in study design, data collection, data analysis, data interpretation, writing of the report, or in the decision to submit for publication. read 2026-10-11 at PMC.
side effects by rate: what each label prints, not a head-to-head trial
the labels' own warning, first: “Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.” the two columns below come from different trials, in different people, under different inclusion rules. read each against its own placebo column, not against the other drug.
| reaction | bupropion SR 300 mg/day (n=376) / bupropion SR 400 mg/day (n=114) vs Placebo (n=385) | PROZAC (N=2869) vs Placebo (N=1673) |
|---|---|---|
| nausea | 13% / 18% vs 8% | 22% vs 9% |
| dry mouth | 17% / 24% vs 7% | 9% vs 6% |
| diarrhea | 5% / 7% vs 6% | 11% vs 7% |
| constipation | 10% / 5% vs 7% | 5% vs 4% |
| insomnia | 11% / 16% vs 6% | 19% vs 10% |
| somnolence | 2% / 3% vs 2% | 12% vs 5% |
| dizziness | 7% / 11% vs 5% | 9% vs 6% |
| headache | 26% / 25% vs 23% | 21% vs 19% |
| tremor | 6% / 3% vs 1% | 9% vs 2% |
| sweating | 6% / 5% vs 2% | 7% vs 3% |
| decreased appetite | 5% / 3% vs 2% | 10% vs 3% |
| anxiety | 5% / 6% vs 3% | 12% vs 6% |
| nervousness | 5% / 3% vs 3% | 13% vs 8% |
| vomiting | 4% / 2% vs 2% | 3% vs 2% |
- Wellbutrin (bupropion): 9% (300 mg/day); 11% (400 mg/day) stopped for an adverse reaction vs 4% on placebo (Wellbutrin XL label, SPL effective 2026-02-10).
- Prozac (fluoxetine): the label prints no discontinuation rate in the section we transcribed.
what makes each table, in the labels' words
- Wellbutrin XL (bupropion), SPL effective 2026-02-10, 6 ADVERSE REACTIONS / 6.1 Clinical Trials Experience, extended-release tablets (Wellbutrin XL); the MDD table below is from trials of the sustained-release (SR) formulation — see caption. inclusion rule: “Table 3 summarizes the adverse reactions that occurred in placebo-controlled trials in patients treated with bupropion HCl sustained-release 300 mg/day and 400 mg/day. These include reactions that occurred in either the 300 mg or 400 mg group at an incidence of 1% or more and were more frequent than in the placebo group.” trials: “Placebo-controlled trials in patients with MDD, bupropion HCl sustained-release 300 mg/day (n=376) and 400 mg/day (n=114) vs placebo (n=385).” DailyMed
- Prozac (fluoxetine), SPL effective 2026-01-08 (the PI carries no printed 'Revised:' footer; only the attached Medication Guide is dated, revised August, 2023), 6 ADVERSE REACTIONS / 6.1 Clinical Trials Experience. inclusion rule: “...treatment-emergent adverse reactions that occurred in 2% or more patients treated with PROZAC and with incidence greater than placebo who participated in US Major Depressive Disorder, OCD, and bulimia controlled clinical trials and US plus non-US Panic Disorder controlled clinical trials.” trials: “Multiple doses of PROZAC have been administered to 10,782 patients with various diagnoses in US clinical trials. In addition, there have been 425 patients administered PROZAC in panic clinical trials. Incidence in Major Depressive Disorder, OCD, bulimia, and Panic Disorder placebo-controlled clinical trials (excluding data from extensions of trials).” DailyMed
every row above was transcribed from the current FDA label on 2026-09-08; the full tables, including the reactions only one label lists, are on side-effect rates, drug vs placebo. the sexual side-effect rows carry each label's own underreporting caveat on the SSRI sexual side effects page.
bupropion (Wellbutrin)
atypical antidepressant (NDRI)
- FDA approval
- 1985 — immediate-release; marketed from 1989 after a seizure signal, Wellbutrin SR followed in 1996 · full approval journey →
- Who takes it (US, 2024)
- 8,042,018 patients · 34,914,025 prescriptions (AHRQ MEPS)2014 → 2024: 25,051,661 → 34,914,025 prescriptions, up 39%Correction (29 September 2026): An earlier version of this section took its numbers from ClinCalc DrugStats, a third-party site that republishes this survey; we now compute them from AHRQ’s public-use files ourselves. It showed 8,042,017 people and 34,895,515 prescriptions for 2024; the file gives 8,042,018 and 34,914,025.
- Who pays (2024)
- Medicare: 9,811,789 claims · 2,224,023 beneficiariesMedicaid: ≥6,860,093 prescriptionsCommercial claims: not published in any public dataset — a real absence, not a zero.
- Boxed warning
- Yes — on the current FDA label. read it in context →
- Adverse-event reports (FAERS)
- Caveat first: FAERS counts unverified REPORTS, not patients or rates — no denominator, and attention inflates reporting. Never compare these counts head-to-head; a longer-marketed, more-prescribed drug accumulates more reports by exposure alone. how to read FAERS →152,137 all-time reports; most-reported terms: drug ineffective, nausea, fatigue
- Legal & safety record
- the full litigation & recall record →
fluoxetine (Prozac)
SSRI antidepressant
- FDA approval
- 1987 · full approval journey →
- Who takes it (US, 2024)
- 6,177,252 patients · 29,517,276 prescriptions (AHRQ MEPS)2014 → 2024: 23,867,189 → 29,517,276 prescriptions; the change is within the survey’s margin of errorCorrection (29 September 2026): An earlier version of this section took its numbers from ClinCalc DrugStats, a third-party site that republishes this survey; we now compute them from AHRQ’s public-use files ourselves. It said prescriptions were up 24% since 2014; that change is within the survey’s margin of error, so we no longer state a direction.
- Who pays (2024)
- Medicare: 7,496,788 claims · 1,487,371 beneficiariesMedicaid: ≥6,359,320 prescriptionsCommercial claims: not published in any public dataset — a real absence, not a zero.
- Boxed warning
- Yes — on the current FDA label. read it in context →
- Adverse-event reports (FAERS)
- Caveat first: FAERS counts unverified REPORTS, not patients or rates — no denominator, and attention inflates reporting. Never compare these counts head-to-head; a longer-marketed, more-prescribed drug accumulates more reports by exposure alone. how to read FAERS →131,850 all-time reports; most-reported terms: drug ineffective, nausea, fatigue
- Legal & safety record
- the full litigation & recall record →
questions for your prescriber, built from this page
this page does not tell you to start, stop or switch anything. it arms the conversation where that decision belongs. take these in:
- which of Wellbutrin and Prozac did you have in mind first, and what in my history points that way?
- these two are different classes (atypical antidepressant (NDRI); SSRI antidepressant). what are they each being asked to do for me, and is that use on the label or off it?
- the label lists these reactions above placebo for the one you're suggesting. which of them should i expect in the first weeks, and which would make you want to hear from me the same day?
- how long were the approval trials, and what do we know past that point?
- how will we judge whether it is working, by when, and what is the plan if it isn't?
- if i ever want to come off it, how is that done, and over how long?
- is there a cheaper generic or a formulation that changes the dosing, and does my insurance prefer one of these two?
the longer checklist, for any antidepressant, is questions to ask before starting antidepressants. if you are already on one and it feels like it stopped working, that has its own page.
What the warnings mean, drug by drug
Each explainer reads one drug's current FDA label and the studies in our library, in both directions: the boxed warnings with the label's own numbers, the trials behind the approval and how long they ran, side effects by rate, and the research since.
Questions people search
Is Wellbutrin or Prozac better?
No honest page can answer that in one line. Head-to-head differences between comparable psychiatric medications are usually smaller than rankings suggest, and which fits you depends on your history, other medications, and side-effect trade-offs, a prescriber conversation. What can be compared is the public record (usage, payers, label warnings, approval history, litigation), which is what this page does, with sources.
Is Wellbutrin the same as bupropion, and Prozac the same as fluoxetine?
Wellbutrin is a brand name for bupropion. Prozac is a brand name for fluoxetine. bupropion is an atypical antidepressant (NDRI); fluoxetine is a SSRI antidepressant. This page uses the generic names because the federal datasets do.
Which has fewer side effects, Wellbutrin or Prozac?
The two FDA labels cannot be compared head to head, in their own words, because each drug's trials ran in different people under different rules. What each label prints: Wellbutrin (bupropion): 9% (300 mg/day); 11% (400 mg/day) stopped for an adverse reaction vs 4% on placebo (Wellbutrin XL label, SPL effective 2026-02-10). Prozac (fluoxetine): the label prints no discontinuation rate in the section we transcribed. The page shows the reactions both labels list, each against its own placebo column. In the 2018 Lancet network meta-analysis, all-cause dropout against placebo was 0.96 for bupropion and 0.88 for fluoxetine.
Is Wellbutrin or Prozac more effective for depression?
In the 2018 Lancet network meta-analysis of 522 trials and 116,477 adults with major depressive disorder, both beat placebo on response at about 8 weeks: bupropion odds ratio 1.58 (95% CrI 1.35 to 1.86), fluoxetine 1.52 (1.40 to 1.66). The authors described the differences between drugs as mostly modest, with wide intervals. The certainty of evidence was moderate to very low, 78% of the trials were industry funded, and the pooled effect of all antidepressants against placebo was a standardised mean difference of 0.30. None of that says which one fits you.
Which is prescribed more, Wellbutrin or Prozac?
The page shows federal survey estimates we compute from AHRQ’s Medical Expenditure Panel Survey public-use files for both bupropion and fluoxetine: patients and prescriptions in the latest reliable year, and the yearly series from 2014 where AHRQ’s reliability rule allows it, with a direction stated only when the change is larger than the survey’s margin of error. Prescription volume reflects habits, prices, and marketing as much as evidence, so it is context, not a verdict.
Where these numbers come from
- Patients and prescriptions: computed by us from AHRQ's public-use Medical Expenditure Panel Survey Prescribed Medicines files, 2014 (HC-168A) to 2024 (HC-254A), with AHRQ's reliability rule (a year with fewer than 60 respondents or a relative standard error over 50% is not shown) — counts of people filling prescriptions, not outcomes. A direction is stated only when the change is larger than the survey's margin of error. Until 29 September 2026 these came from ClinCalc DrugStats, a third-party site; see the correction under each drug where a figure changed.
- Medicare/Medicaid: CMS public datasets; commercial insurance publishes no per-drug series, so it renders as an absence, never a synthesized number.
- Label facts: the drugs' current FDA labels via DailyMed — quoted in context on each drug's approval-journey page.
- FAERS: openFDA — reports, never rates; the caveat travels above every count.
- Litigation: court records and regulator documents only, on the linked record pages; settled is never adjudicated.
Explore both drugs in depth: /m/bupropion · /m/fluoxetine · or the whole library →