Wellbutrin (bupropion) causes dry mouth, constipation, insomnia, and tremor more often than most other side effects, with dry mouth affecting roughly 28% of patients in clinical trials and constipation affecting 26%. Because it works on dopamine and norepinephrine rather than serotonin, its side effect profile is noticeably different from SSRIs like Prozac or Zoloft. Some effects that are common with those medications, particularly sexual dysfunction and weight gain, are rare with Wellbutrin.
The Most Common Side Effects
In FDA-reviewed clinical trials of 323 patients taking 300 to 600 mg daily for three to four weeks, these side effects appeared most frequently: agitation (32%), dry mouth (28%), constipation (26%), headache (26%), weight loss (23%), excessive sweating (22%), nausea or vomiting (23%), dizziness (22%), tremor (21%), sedation (20%), and insomnia (19%). Blurred vision affected about 15% of patients, and a faster-than-normal heart rate showed up in about 11%.
Many of these also occurred in the placebo group at notable rates, which means some of the symptoms overlap with depression itself. Tremor is one clear standout: it affected 21% of patients on Wellbutrin compared to just 8% on placebo, making it one of the side effects most clearly tied to the drug rather than the underlying condition.
In studies of the sustained-release formulation at more typical doses (100 to 400 mg per day), the rates were lower. Dry mouth dropped to about 16% versus 7% on placebo, nausea to 12.5% versus 7.5%, and insomnia to 10.5% versus 6.5%. The extended-release version also tends to cause fewer sleep problems than the immediate-release or twice-daily forms.
Why It Feels Different From Other Antidepressants
Most antidepressants work primarily on serotonin. Wellbutrin doesn’t. It blocks the reabsorption of dopamine and norepinephrine, with essentially no serotonin activity. This explains its unique side effect profile in both directions: it avoids many serotonin-related problems but creates others tied to increased dopamine and norepinephrine activity.
Boosting norepinephrine is what drives the dry mouth, agitation, and occasional blood pressure increases. The dopamine side is responsible for the constipation, insomnia, and the restless, activated feeling some people notice in the first week or two. That activation can feel like too much caffeine, with jitteriness, difficulty sitting still, and trouble winding down at night.
Sexual Side Effects and Weight
One of the main reasons prescribers choose Wellbutrin over an SSRI is its low rate of sexual side effects. SSRIs are the antidepressants most likely to cause problems with arousal, orgasm, or desire. Wellbutrin is among the least likely. In clinical trials, rates of decreased libido and sexual dysfunction with bupropion were close to placebo levels. It is sometimes added to an SSRI specifically to counteract sexual side effects caused by that medication.
Weight is a similar story. While many antidepressants are associated with weight gain over time, Wellbutrin tends to cause modest weight loss. A 2024 meta-analysis of 25 randomized trials with over 12,000 participants found that bupropion led to an average weight loss of about 8 pounds (3.7 kg) compared to placebo. In routine clinical settings, patients on bupropion-based regimens lost roughly 5% of their body weight at six months. This effect is dose-dependent and typically levels off after 6 to 12 months.
Seizure Risk
Seizures are the most well-known serious risk with Wellbutrin, though they remain uncommon. At doses of 450 mg per day or less, seizures occur in about 0.3% of patients. With the sustained-release form, the rate drops further to 0.15% to 0.4% at standard doses. At 600 mg per day or higher, the risk climbs to 2% to 3%, which is why there is a firm dose ceiling.
Several factors lower your seizure threshold further while on bupropion. These include eating disorders (bulimia and anorexia), a history of seizures, abrupt withdrawal from alcohol or sedatives, and taking other medications that also lower the seizure threshold. If you drink heavily and then stop suddenly, that combination with bupropion is a particular concern because alcohol withdrawal itself can trigger seizures.
Mood Changes and Suicidal Thoughts
Wellbutrin carries an FDA boxed warning about suicidal thoughts and behavior, the same warning applied to all antidepressants. In short-term clinical trials, antidepressants increased the risk of suicidal thinking in children, adolescents, and young adults under 25. This increased risk was not seen in adults over 24, and in people 65 and older, antidepressants actually reduced the risk.
Beyond suicidality, some patients experience increased anxiety, hostility, or confusion in the early weeks of treatment. In trials, agitation was reported by 32% of patients on Wellbutrin versus 22% on placebo, and confusion by 8% versus 5%. These neuropsychiatric effects are most noticeable during the first few weeks and often settle as your body adjusts to the medication.
Blood Pressure and Heart Effects
Wellbutrin can raise blood pressure, which showed up in about 4% of clinical trial participants compared to 2% on placebo. A faster heart rate occurred in about 11% of patients. These cardiovascular effects stem from increased norepinephrine activity and are typically mild, but they matter if you already have high blood pressure or heart disease. Blood pressure monitoring during the first few months of treatment helps catch any meaningful increases early.
Stopping Wellbutrin
Bupropion is generally considered to have a milder withdrawal profile than SSRIs, but stopping abruptly can still cause symptoms. Common withdrawal effects include anxiety, irritability, fatigue, increased appetite, trouble sleeping, headaches, and general body aches.
Tapering schedules depend on your dose and how long you’ve been taking it. If you’re on 300 mg or more, a typical approach is stepping down to 150 mg for one to two weeks before stopping entirely. At 150 mg or less, a taper may not be necessary. The timeline can range from a few days to a few weeks depending on how your body responds.