Does Bupropion Cause Constipation? And What to Do About It

Bupropion can cause constipation, and it does so more often than placebo in clinical trials. A large network meta-analysis found that bupropion roughly doubled the odds of constipation compared to placebo, with an odds ratio of about 2.38.¹ That puts it squarely in the middle of the pack among antidepressants, not the worst offender but far from innocent. The good news is that the problem is manageable for most people, and there are concrete steps you can take before resorting to switching medications.

How Bupropion Stacks Up Against Other Antidepressants

People sometimes assume bupropion is gentle on the gut because it is not an SSRI and does not carry the nausea reputation of drugs like sertraline. That assumption is half right. Bupropion does tend to cause less nausea than many SSRIs, but constipation is a different story. In the same meta-analysis that pooled data across dozens of randomized trials, 15 out of 20 antidepressants produced significantly more constipation than placebo. The older tricyclic antidepressants were the worst, with amitriptyline and clomipramine roughly quadrupling the odds. Bupropion landed in a cluster of drugs with about double the risk, alongside paroxetine, trazodone, desvenlafaxine, and duloxetine.¹ A handful of SSRIs, including fluoxetine, sertraline, citalopram, and escitalopram, did not show a significantly higher constipation rate than placebo.

This matters if you and your prescriber are weighing options. If constipation is already a concern for you, knowing that bupropion carries a moderate risk while certain SSRIs carry almost none could influence the conversation. On the other hand, bupropion has advantages that those SSRIs do not, including lower rates of sexual dysfunction and weight gain, so the tradeoff is rarely straightforward.

Why Bupropion Slows Things Down

Bupropion works primarily by blocking the reuptake of norepinephrine and dopamine, but it also interacts with other receptor systems in ways that affect the gut. One mechanism that has gotten attention involves serotonin receptors in the digestive tract. Researchers have shown that bupropion and its main metabolite, hydroxybupropion, inhibit a specific type of serotonin receptor (5-HT3A) that plays a role in gut motility and the wave-like contractions that push food through your intestines.² When those receptors are blocked, the signals that coordinate peristalsis get dampened, and transit through the colon slows.

Bupropion’s norepinephrine effects likely contribute as well. Norepinephrine influences the sympathetic nervous system, and increased sympathetic tone tends to reduce gut motility. The combination of these pathways helps explain why constipation is a real and predictable side effect rather than a fluke that only a few people experience.

When Constipation Typically Appears and Whether It Fades

Gastrointestinal side effects from antidepressants tend to show up early. In a published case report, a man prescribed extended-release bupropion 150 mg daily developed constipation within the first three weeks of treatment, severe enough to cause hemorrhoids from straining.³ Adverse effects from antidepressants in general are common early in treatment and are one of the main reasons people stop taking their medication prematurely.⁴

Whether bupropion-related constipation eases on its own over time varies. Some people find that their body adjusts after the first month or two, and bowel habits return closer to normal. Others deal with it as long as they stay on the medication. In the case report above, the patient’s constipation resolved after he stopped bupropion on his own, about a week before a planned surgical procedure.³ That kind of resolution after discontinuation strongly suggests the drug was the cause, but stopping the medication is not usually the first or best move. If bupropion is helping your depression, there are interventions worth trying before giving it up.

People Who Are Already at Higher Risk

Constipation does not start from the same baseline for everyone. A general practice study found that antidepressants as a class carried an odds ratio of about 1.9 for chronic constipation, with a population attributable risk of roughly 8 percent, meaning antidepressants accounted for a meaningful share of constipation cases in the population studied.⁵ But other medications stacked on top of an antidepressant increase the risk further. The same study identified opioids, diuretics, antihistamines, anticonvulsants, and antispasmodics as independent risk factors for chronic constipation.⁵

If you take bupropion alongside any of those drug classes, you are layering constipation risk. This is especially relevant for people managing pain with opioids, people on diuretics for blood pressure, or those taking over-the-counter antihistamines regularly for allergies. Older adults are disproportionately affected because they are more likely to be on multiple medications, and aging itself slows gut transit. Neurological conditions such as Parkinson’s disease or multiple sclerosis carry their own strong independent association with constipation, and adding an antidepressant on top makes things worse.

It is also worth flagging the combination drug naltrexone/bupropion, prescribed for weight management. In clinical trials of that combination, constipation was among the most commonly reported side effects alongside nausea, headache, and vomiting.⁶ Naltrexone, an opioid receptor antagonist, has its own effects on the gut, and the combination may amplify the constipation risk beyond what bupropion alone would produce.

The Depression-Constipation Connection That Exists Without Any Medication

Here is a wrinkle that complicates the picture: depression itself is linked to constipation. An analysis of more than 12,000 adults in the United States found that people with constipation were significantly more likely to have major depression than those without it, even after researchers adjusted for diet, physical activity, BMI, and use of SSRIs. The adjusted odds ratio was about 2.2, meaning the association was strong and not easily explained away by medication or lifestyle alone.⁷

This means that if you start bupropion and develop constipation, the drug might be the cause, but the underlying depression could also be a contributor, or both could be working together. Depression is associated with reduced physical activity, altered eating patterns, and changes in autonomic nervous system function, all of which slow the gut. Separating the effect of the medication from the effect of the condition it treats is genuinely difficult in practice. If constipation was already present before starting bupropion, it may not be fair to blame the drug entirely.

What You Can Do About It

Most cases of bupropion-related constipation respond to straightforward interventions, and you should try the simplest approaches first before escalating.

Fiber, Fluid, and Movement

Increasing dietary fiber is the most studied first-line approach for antidepressant-induced constipation. A clinical study in depressed inpatients found that daily fiber supplementation with cellulose and citrus pectin significantly improved stool frequency and reduced the severity of constipation, with physical activity level also playing an independent role.⁸ You do not need a specialty supplement. Whole grains, beans, lentils, vegetables, and fruits all contribute. Aim for a gradual increase, because adding too much fiber too quickly can cause bloating and gas, which makes the problem feel worse before it feels better.

Hydration matters more than people think. Fiber absorbs water to soften stool, and if you increase fiber without increasing fluid intake, you can actually make constipation worse. There is no magic number of glasses per day, but if your urine is consistently dark, you are likely not drinking enough. Physical activity helps too. Even moderate daily movement like a 20- to 30-minute walk can stimulate gut contractions. Depression can sap motivation for exercise, so this recommendation is easier to give than to follow, but even small increases in activity count.

Over-the-Counter Options

If diet and lifestyle changes are not enough, osmotic laxatives are generally considered the safest next step. Polyethylene glycol (sold as MiraLAX and similar brands) at a standard dose of about 17 grams daily is commonly recommended for medication-induced constipation.⁹ It works by pulling water into the colon and is safe for daily use in most adults. Docusate sodium (Colace) is a stool softener that is gentler but often less effective on its own. Stimulant laxatives like bisacodyl or senna work faster but are best reserved for occasional use rather than daily reliance, as the gut can develop tolerance to them over time.

A practical order of operations might look like this:

Week one: Add fiber-rich foods gradually and increase fluid intake.
Week two: If no improvement, add polyethylene glycol daily.
Week three onward: If still struggling, talk to your prescriber about adjusting the bupropion dose or considering alternatives.

When to Talk to Your Prescriber About Switching

If constipation persists despite fiber, fluids, exercise, and a daily osmotic laxative, it is reasonable to discuss a medication change. The meta-analysis data mentioned earlier show that certain SSRIs, including fluoxetine, sertraline, citalopram, and escitalopram, did not significantly increase constipation risk above placebo.¹ Switching from a constipation-prone drug to one of these may be worth considering, depending on how well bupropion is controlling your depression and whether the SSRIs would introduce different side effects you want to avoid.

Dose adjustments can also help. Constipation is often dose-dependent, so lowering the dose slightly, if clinically appropriate, may reduce the side effect without eliminating the antidepressant benefit. This is a decision to make with your prescriber, not on your own, because stopping or reducing bupropion abruptly can affect your mood stability.

Why Side Effects Like Constipation Matter More Than They Seem

Constipation might sound like a minor inconvenience compared to depression, but gastrointestinal side effects are one of the leading reasons people stop taking their antidepressants.⁴ Research suggests that as many as one in four patients discontinue antidepressants because of side effects they find hard to tolerate, and clinicians tend to underestimate how common and bothersome those side effects are.¹⁰ Others keep taking their medication but experience a diminished quality of life because of ongoing discomfort.¹⁰

The problem compounds because stopping an antidepressant prematurely increases the risk of relapse. A systematic review emphasized that the specific tolerability profile of each antidepressant should be considered at the point of prescribing, not dealt with retroactively after the patient has already become frustrated.¹¹ If you are already experiencing constipation, raising it with your prescriber is not complaining about something trivial. It is protecting the treatment itself.

The Gap Between How Constipation Feels and What Tests Show

One surprising finding in the research is that subjective reports of constipation do not always line up with objective measurements. A study that compared patients’ self-reported gastrointestinal symptoms with objective measures like colonic transit time and colon volume found no correlation between the two.¹² In plain terms, someone who feels constipated may have perfectly normal transit through their colon, and vice versa.

This does not mean your symptoms are imagined. It means that constipation is a complex experience involving rectal sensation, pelvic floor coordination, stool consistency, and perception of effort, not just how fast food moves through you. It also means that if you report constipation and your doctor orders a transit study that comes back normal, the finding does not invalidate your experience. It just means the problem may be about sensation or coordination rather than raw transit speed, and treatment might need to address those dimensions too, potentially with pelvic floor therapy or adjustments to stool consistency rather than transit-targeting laxatives.

Bupropion’s Effects on the Gut Microbiome

Emerging animal research hints at another layer to the bupropion-gut connection. A 2025 study in rats under chronic stress found that oral bupropion significantly changed the composition of gut bacteria, increasing populations of certain beneficial species like Romboutsia and Muribaculum while reducing potentially harmful ones such as Staphylococcus and Streptococcus.¹³ Whether these microbiome shifts contribute to constipation, protect against it, or do something else entirely is not yet clear.

The gut microbiome is deeply involved in regulating bowel motility, fluid secretion, and the signals between the gut and the brain. Disruptions in microbial balance have been linked to both constipation and diarrhea in various contexts. If bupropion reshapes the microbial landscape, that could be one more pathway through which it influences bowel function. This is still early-stage science and limited to animal models, so it would be premature to draw practical conclusions. But it underlines that bupropion’s effects on the gut are more complex than a simple receptor-blocking story, and future research may open new avenues for managing the side effects.

1
PubMed Central. Comparative gastrointestinal effects of antidepressants for the acute treatment of adults with major depressive disorder: a network and dose‒response meta-analysis
2
PubMed Central. The antidepressant bupropion is a negative allosteric modulator of serotonin type 3A receptors
3
PubMed. Severe constipation associated with extended-release bupropion therapy
4
PubMed Central. Adverse effects from antidepressant treatment: randomised controlled trial of 601 depressed individuals
5
PubMed. Risk factors for chronic constipation based on a general practice sample
6
PubMed. The efficacy and safety of the naltrexone/bupropion combination for the treatment of obesity: an update
7
PubMed Central. Association between constipation and major depression in adult Americans: evidence from NHANES 2005–2010
8
Journal of Korean Academy of Psychiatric and Mental Health Nursing. Effect of Dietary Fiber Supplement on Antidepressant Induced Constipation in depressed inpatients
9
Psychopharmacology Institute. Does Bupropion Cause Constipation? And What to Do About It – Section: Management and Treatment Strategies
10
PubMed Central. Toward achieving optimal response: understanding and managing antidepressant side effects
11
PubMed. Gastrointestinal side effects associated with antidepressant treatments in patients with major depressive disorder: A systematic review and meta-analysis
12
PubMed. Comparison of subjective and objective measures of constipation – Employing a new method for categorizing gastrointestinal symptoms
13
PubMed. Bupropion administration significantly impacts the gut microbiome, serum metabolites, and immune factors in chronic stress depression rats