What Is Bupropion (Wellbutrin, Zyban)? Uses, Side Effects & Warnings

Bupropion is a unique antidepressant that does not belong to the SSRI or SNRI classes. It is classified as a norepinephrine-dopamine reuptake inhibitor (NDRI) and is chemically related to phenethylamines. The same molecule is sold under two brand names for two different purposes: Wellbutrin (and its extended-release forms, Wellbutrin SR and Wellbutrin XL) for depression and seasonal affective disorder, and Zyban for smoking cessation. It is available in strengths of 75 mg and 100 mg (immediate-release), 100 mg and 150 mg (sustained-release SR), and 150 mg and 300 mg (extended-release XL).

What Bupropion Is Used For

Bupropion is FDA-approved for major depressive disorder, seasonal affective disorder (SAD), and as an aid to smoking cessation. For depression, it is considered a first-line treatment alongside SSRIs and SNRIs, particularly for patients concerned about sexual side effects or weight gain. For seasonal affective disorder, Wellbutrin XL is specifically approved for preventive use — started in the autumn before symptoms appear.

As Zyban, bupropion is one of the two most effective non-nicotine pharmacological aids for quitting smoking (alongside varenicline/Chantix). It reduces nicotine cravings and withdrawal symptoms, likely through its effects on dopamine — the same neurotransmitter pathway activated by nicotine. Off-label, bupropion is frequently used for ADHD (particularly in adults), bipolar depression, and to counteract sexual dysfunction caused by SSRIs.

How Bupropion Works

Unlike SSRIs and SNRIs, bupropion has virtually no effect on the serotonin system. Instead, it inhibits the reuptake of both dopamine and norepinephrine, increasing the availability of these neurotransmitters in the synapse. Dopamine is involved in motivation, pleasure, and reward — functions often diminished in depression and addiction. Norepinephrine plays roles in alertness, concentration, and the stress response.

This mechanism distinguishes bupropion from other antidepressants in important ways. Because it does not significantly affect serotonin, it lacks the sexual side effects (delayed orgasm, decreased libido) that are so common with SSRIs and SNRIs. It also does not cause weight gain and may actually produce modest weight loss in some patients — an important consideration given that weight gain is a leading reason people stop antidepressants.

Common Side Effects

• Insomnia and sleep disturbances (take morning doses to minimize this)
• Dry mouth
• Headache
• Nausea (usually mild and transient)
• Increased heart rate (tachycardia)
• Agitation, restlessness, or anxiety — particularly early in treatment
• Tremor
• Sweating
• Constipation
• Decreased appetite and weight loss

Notably absent from bupropion's side effect profile are the sexual dysfunction and weight gain that affect many patients on SSRIs. This makes it particularly attractive for patients who experienced those issues with other antidepressants.

Important Warnings

Bupropion is contraindicated in patients with a seizure disorder or eating disorders. It should not be used within 14 days of stopping an MAO inhibitor. It should not be used with other formulations of bupropion simultaneously (e.g., taking Wellbutrin and Zyban together would double the dose).

Key Drug Interactions

Bupropion is a potent inhibitor of the CYP2D6 enzyme, which metabolizes many common medications including certain beta-blockers (metoprolol, propranolol), antipsychotics, and opioid pain medications such as codeine and tramadol. Codeine and tramadol require CYP2D6 to be converted to their active forms; bupropion may reduce their effectiveness and increase the risk of adverse effects.

MAO inhibitors are contraindicated due to the risk of hypertensive crisis. Combining bupropion with other medications that lower the seizure threshold (such as tramadol, antipsychotics, or theophylline) increases seizure risk. Alcohol use should be minimized, as alcohol followed by abrupt cessation also lowers the seizure threshold.

Frequently Asked Questions

Why doesn't bupropion cause sexual side effects like SSRIs?

SSRI-related sexual dysfunction is primarily linked to serotonin activity at 5-HT2 receptors, which inhibits dopamine release in pathways associated with sexual arousal and orgasm. Because bupropion works on dopamine and norepinephrine rather than serotonin, it avoids this mechanism. In fact, bupropion is sometimes added to SSRI regimens specifically to counteract SSRI-induced sexual dysfunction.

Is bupropion good for anxiety?

Bupropion is generally considered less effective for anxiety than SSRIs or SNRIs and may actually worsen anxiety or agitation in some patients, at least initially. It is not a first-line treatment for anxiety disorders, and patients with significant anxiety comorbidity are often better served by SSRIs or SNRIs. If anxiety occurs, the dose may need to be reduced or the medication reconsidered.

How does bupropion work for quitting smoking?

Nicotine activates dopamine reward pathways in the brain, creating the pleasurable sensation of smoking. Bupropion's dopamine-enhancing effects are thought to partially substitute for nicotine's action on these pathways, reducing the urge to smoke. It is typically started one to two weeks before the planned quit date to allow therapeutic levels to build, and is used for 7–12 weeks.

Can bupropion be used with SSRIs?

Yes — combining bupropion with an SSRI is a well-established strategy in psychiatry, used to augment antidepressant response or to counter SSRI-induced sexual dysfunction. However, because bupropion inhibits CYP2D6 — an enzyme that metabolizes many SSRIs including fluoxetine and paroxetine — close monitoring for side effects is important, as SSRI levels may increase with the combination.