Wellbutrin XL (Bupropion).
What It Does, Side Effects, and What to Expect.

Bupropion -- sold as Wellbutrin XL, Wellbutrin SR, and Zyban -- is an antidepressant that works completely differently from SSRIs and SNRIs. It targets dopamine and norepinephrine, not serotonin. That different mechanism gives it a distinct side effect profile: no sexual side effects, weight-neutral to weight-negative, and more activating than sedating. For the right patient, these are significant advantages. Here is what to know.

What Is Bupropion?

Bupropion is a norepinephrine-dopamine reuptake inhibitor (NDRI). It blocks the reuptake of both norepinephrine and dopamine, increasing their availability in the brain. It has little to no action on serotonin -- which is why it lacks the sexual side effects and the weight-promoting effects associated with SSRIs and SNRIs.

FDA-approved uses:

• Major depressive disorder (MDD) -- both Wellbutrin XL and Wellbutrin SR
• Seasonal affective disorder (SAD) -- Wellbutrin XL specifically; the only antidepressant with an FDA indication for SAD
• Smoking cessation -- as Zyban (same molecule, different brand)

Widely used off-label for: ADHD, sexual dysfunction caused by SSRIs (added on to offset those effects), and weight management.

XL vs. SR: What Is the Difference?

Wellbutrin XL -- extended release, taken once daily in the morning. The most common formulation for depression and SAD. Provides steady blood levels throughout the day.

Wellbutrin SR -- sustained release, typically taken twice daily. Used when a divided dose is preferred or when starting at a lower total daily dose.

Both contain the same molecule. The XL formulation is generally preferred for convenience and consistency of blood levels. Starting dose is 150 mg XL once daily; the typical therapeutic dose is 300 mg; the maximum is 450 mg.

What Makes Wellbutrin Different from SSRIs

• No sexual side effects. This is the most clinically significant difference. SSRIs and SNRIs cause sexual dysfunction in 30 to 40 percent of users. Bupropion has essentially no sexual side effects. It is sometimes added to an existing SSRI specifically to counteract SSRI-induced sexual dysfunction.
• Weight-neutral to weight-negative. Bupropion is associated with modest weight loss or no weight change in most patients -- a significant advantage over many other antidepressants. See our post on antidepressants and weight gain.
• More activating. The dopamine and norepinephrine mechanism produces an energizing effect rather than the sedation some people experience on SSRIs. This is helpful for patients with fatigue and low motivation but can worsen insomnia and anxiety.
• Does not work for anxiety. Because bupropion is not serotonergic, it does not treat anxiety disorders. For patients whose depression is accompanied by significant anxiety, bupropion alone is often not sufficient -- and in some patients it can worsen anxiety and restlessness.

Side Effects

• Insomnia -- one of the most common; taking it before noon reduces the impact on sleep
• Dry mouth
• Headache
• Nausea -- less than SSRIs but can occur, especially early
• Increased heart rate
• Agitation or restlessness -- particularly in the first weeks
• Constipation

The Seizure Warning

Bupropion lowers the seizure threshold in a dose-dependent way. This is why it has absolute contraindications in certain situations:

• Eating disorders (anorexia or bulimia): Electrolyte abnormalities from restrictive eating or purging significantly increase seizure risk with bupropion. This is an absolute contraindication.
• Seizure disorder or history of seizures: Bupropion should be avoided or used only with careful risk-benefit consideration.
• Abrupt discontinuation of alcohol or benzodiazepines: Withdrawal states also lower the seizure threshold.
• High doses: Risk increases significantly above 450 mg/day, which is why the dose ceiling exists.

For patients without these risk factors, the seizure risk at standard doses is low (less than 0.1 percent). It should not be dismissed, but it should not cause unnecessary alarm in appropriate patients.

Wellbutrin and ADHD

Bupropion is used off-label for ADHD, and its dopaminergic mechanism makes pharmacological sense for this use. The evidence is meaningful but weaker than for stimulants -- most providers use it for ADHD when stimulants are not tolerated, contraindicated, or when the patient also needs depression treatment. See our dedicated post on Wellbutrin for ADHD for more detail.