Bupropion HCl ER (SR) 150 mg is a sustained-release tablet of the antidepressant bupropion, most commonly prescribed for major depression and as a smoking-cessation aid. It works differently from the SSRIs that dominate antidepressant prescribing: instead of targeting serotonin, bupropion blocks the reuptake of dopamine and norepinephrine, which gives it a distinct side-effect profile that many people find more tolerable, particularly when it comes to sexual function and weight. The “SR” label means the drug releases gradually over roughly 12 hours, so it is typically taken twice a day, though plenty of prescribers start patients at one 150 mg tablet each morning.
How Bupropion Works in the Brain
Bupropion’s main action is dual inhibition of norepinephrine and dopamine reuptake. It does not meaningfully affect serotonin, which sets it apart from SSRIs and SNRIs.1PubMed Central. A Review of the Neuropharmacology of Bupropion, a Dual Norepinephrine and Dopamine Reuptake Inhibitor By keeping more dopamine and norepinephrine available in the synaptic gap, it helps restore motivation, energy, and concentration, symptoms that are often the most disabling parts of depression.
There is also a secondary mechanism that matters for smokers. Bupropion acts as a noncompetitive antagonist of nicotinic acetylcholine receptors. In practical terms, it blunts the rewarding “hit” that nicotine delivers to the brain, while also reducing cravings through its dopamine-boosting effect.2PubMed. Is the inhibition of nicotinic acetylcholine receptors by bupropion involved in its clinical actions? This dual action on both neurotransmitter reuptake and nicotinic receptors is the basis for its FDA approval under the brand name Zyban for tobacco dependence.
What “SR” and “150 mg” Actually Mean
Bupropion comes in three release formulations. The immediate-release (IR) version, the original, requires dosing three times a day. The sustained-release (SR) version extends absorption so you can take it twice daily at most. And the extended-release (XL) version lasts a full 24 hours, requiring just one pill. When your prescription says “ER (SR),” you have the twice-daily formulation. The 150 mg strength is the standard building block: many people take one tablet daily as a starting dose for depression, then move to 150 mg twice daily if needed.
In head-to-head comparisons for smoking cessation, SR and XL deliver a similar total amount of drug into the bloodstream over the course of a day, as measured by the area under the plasma-concentration curve. The XL version produces a slightly lower peak blood level and takes longer to reach that peak, which may translate to marginally less insomnia for some people.3PubMed Central. Bupropion XL and SR Have Similar Effectiveness and Adverse Event Profiles When Used to Treat Smoking Among Patients at a Comprehensive Cancer Center Clinically, both formulations appear equally effective. The practical difference is convenience: people tend to stick with once-daily XL longer than twice-daily SR. In one large managed-care study, the average time patients stayed on XL was roughly 128 days compared to about 82 days for SR, and those on XL were almost twice as likely to maintain good adherence.4PubMed. Persistence with once-daily versus twice-daily bupropion for the treatment of depression in a large managed-care population
A web-based survey of SR users found that the most common reason for missing doses was simply forgetting, with about half of twice-daily users and nearly two thirds of three-times-daily users citing forgetfulness. Roughly three quarters of those taking it twice daily expressed interest in switching to a once-daily formula.5PubMed. An assessment of patient preference and adherence to treatment with Wellbutrin SR: a web-based survey If you find yourself regularly missing the second dose, it is worth asking your prescriber about XL.
Depression at the 150 mg Dose
The 150 mg SR dose, taken either once or twice daily, has been shown to be more effective than placebo in treating major depression. In a multicenter trial, patients on 150 mg daily and those on 300 mg daily (150 mg twice) both showed significantly reduced depression scores on standardized scales by day 56, and the once-daily 150 mg dose appeared to perform at least as well as the twice-daily regimen.6Clinical Therapeutics. A multicenter evaluation of the efficacy and safety of 150 and 300 mg/d sustained-release bupropion tablets versus placebo in depressed outpatients This is why many clinicians will start at 150 mg once daily and only increase the dose if the initial response is insufficient after a few weeks.
That said, bupropion is not the best fit for every type of depression. It tends to be most helpful when low energy, poor concentration, and lack of motivation are the dominant complaints. People whose depression centers on severe anxiety or agitation sometimes find bupropion’s activating quality uncomfortable, at least initially. Prescribers often choose bupropion specifically when a patient has had sexual side effects or weight gain on an SSRI, since bupropion’s profile is much more favorable on both counts.
Smoking Cessation
Bupropion SR 150 mg twice daily is one of the first-line pharmacotherapies for quitting smoking. Across multiple trials, it roughly doubles the odds of staying smoke-free at six months or longer compared to placebo. A meta-analysis of bupropion SR for smoking cessation estimated a combined odds ratio of about 2.5 for sustained abstinence at six to twelve months.7Mayo Clinic Proceedings. Bupropion for the Treatment of Tobacco Dependence: Retrospective Review of Evidence and Clinical Recommendations In absolute terms, roughly one in five smokers who use bupropion manage to quit, compared to about one in ten on placebo.8PubMed Central. The use of bupropion SR in cigarette smoking cessation
A large effectiveness trial in a real-world healthcare setting tested 150 mg and 300 mg daily and found that nonsmoking rates at three months were about 24% and 31%, respectively. By 12 months the gap between the two doses narrowed and was no longer statistically significant, though participants on the higher dose reported less desire to smoke.9JAMA Internal Medicine. Effectiveness of Bupropion Sustained Release for Smoking Cessation in a Health Care Setting: A Randomized Trial The takeaway is that the 150 mg dose is a reasonable starting point if you are quitting, and escalating to 300 mg may help with craving control.
Common Side Effects
The most frequently reported side effects at the standard 150 mg twice-daily dose are insomnia, dry mouth, headache, nausea, and anxiety. Of these, only insomnia and dry mouth consistently occurred at significantly higher rates than placebo in clinical trials.10PubMed. Tolerability and safety of sustained-release bupropion in the management of smoking cessation The anxiety and insomnia can be tricky to interpret in smokers who are quitting, since nicotine withdrawal causes the same symptoms. Across depression trials the pattern was similar: dry mouth, nausea, and insomnia were the side effects that stood out above placebo, while vital signs and lab values showed no consistent changes.11Clinical Therapeutics. Safety profile of sustained-release bupropion in depression: Results of three clinical trials
A practical tip: if insomnia is a problem, taking the second dose in the mid-afternoon rather than the evening can help. Some clinicians will also drop back to one 150 mg tablet in the morning for a week or two to let the body adjust before stepping up.
Sexual Side Effects and Weight
This is where bupropion genuinely shines relative to SSRIs, and it is one of the main reasons prescribers reach for it. In a direct comparison, 86% of bupropion-treated patients reported no adverse sexual effects, compared to only 27% of those on SSRIs. Even more striking, 77% of bupropion patients reported at least one aspect of heightened sexual functioning.12PubMed. Comparative sexual side effects of bupropion, fluoxetine, paroxetine, and sertraline For people who have stopped an antidepressant because of sexual dysfunction, bupropion is often the first alternative tried, and it is sometimes added to an SSRI specifically to counteract sexual side effects.
Weight is the other area of advantage. While many antidepressants are associated with weight gain over time, bupropion tends to do the opposite. A systematic review and meta-analysis of randomized trials found that bupropion use was associated with an average weight loss of about 3.7 kg compared to control groups.13PubMed Central. The effects of bupropion alone and combined with naltrexone on weight loss: a systematic review and meta-regression analysis of randomized controlled trials Bupropion is also a component of the combination weight-loss drug naltrexone-bupropion (sold as Contrave), where the two agents have complementary effects on appetite and reward pathways.14PubMed. Bupropion and naltrexone: a review of their use individually and in combination for the treatment of obesity
Seizure Risk and Who Should Avoid It
The most serious rare risk of bupropion is seizures, and it is the reason the drug was briefly pulled from the U.S. market in the 1980s shortly after its initial approval. The original immediate-release formulation, dosed at higher levels than we use today, caused seizures in a small but concerning number of patients. When it was reintroduced, the labeling included stronger dose limits and warnings about high-risk groups. At the currently recommended SR dose of up to 400 mg per day (or 450 mg for XL), the seizure rate is roughly comparable to other antidepressants, around 0.1% at standard doses.
The risk climbs steeply in overdose. Case reports describe generalized seizures, cardiac effects including QRS and QT prolongation, confusion, and agitation after intentional or accidental bupropion overdose.15PubMed Central. Bupropion Misuse by Nasal Insufflation with a Fatal Outcome: Case Report and Review People with eating disorders, particularly bulimia, are at notably higher seizure risk. In a trial that tested bupropion for bulimia, nearly 6% of participants had seizures, leading to a formal contraindication in that population.16International Journal of Neuropsychopharmacology. Evidence-based pharmacotherapy of eating disorders
Beyond eating disorders, bupropion carries heightened seizure risk for people with a history of epilepsy, those in alcohol or benzodiazepine withdrawal, and those on medications that lower the seizure threshold. Anyone with these conditions should discuss the risk explicitly with their prescriber before starting.
Drug Interactions Worth Knowing About
Bupropion and its metabolites are clinically significant inhibitors of the liver enzyme CYP2D6. This enzyme processes a long list of common medications, including certain beta-blockers, antipsychotics, other antidepressants, and some opioid painkillers. Modeling studies have shown that bupropion’s active metabolites, particularly hydroxybupropion, are actually stronger CYP2D6 inhibitors than the parent drug itself.17PubMed Central. Prediction of Drug-Drug Interactions with Bupropion and Its Metabolites as CYP2D6 Inhibitors Using a Physiologically-Based Pharmacokinetic Model In practical terms, adding bupropion to a regimen that includes a drug metabolized by CYP2D6 can raise blood levels of that other drug, sometimes enough to cause side effects. If you start bupropion while already taking another medication, your pharmacist or prescriber should check for interactions.
One interaction that catches people off guard involves tamoxifen, a breast cancer drug. Tamoxifen is a prodrug that depends on CYP2D6 to become active. Bupropion can substantially reduce tamoxifen’s conversion to its active metabolite, potentially undermining its cancer-preventive effect. This is a combination most oncologists actively avoid.
Off-Label Uses That Have Real Evidence
Beyond depression and smoking, bupropion gets prescribed off-label for adult ADHD, where the evidence is modest but real. A Cochrane review found low-quality evidence that bupropion reduced ADHD symptom severity and increased the proportion of adults achieving meaningful clinical improvement, with treated participants about 50% more likely to be rated as improved compared to those on placebo.18PubMed Central. Bupropion for attention deficit hyperactivity disorder (ADHD) in adults In a small head-to-head comparison with methylphenidate, bupropion produced a 64% response rate versus 50% for methylphenidate and 27% for placebo, though neither active drug reached statistical significance against placebo in that particular trial.19PubMed. Bupropion SR vs. methylphenidate vs. placebo for attention deficit hyperactivity disorder in adults It is not a first-line ADHD treatment, but for adults who cannot tolerate stimulants or who also have depression, it fills a useful niche.
Bupropion has also been studied for methamphetamine use disorder, where effective pharmacotherapies are extremely scarce. A placebo-controlled trial found that the combination of injectable naltrexone plus oral bupropion produced a response rate of about 14% versus about 3% for placebo. The absolute numbers are small, but in a condition with almost no proven medications, even a modest effect represents progress.20PubMed Central. Bupropion and Naltrexone in Methamphetamine Use Disorder A meta-analysis of bupropion for amphetamine-type stimulant use disorders confirmed a modest reduction in stimulant use and cravings, with the strongest effects seen in longer trials and in male participants.21PubMed. Bupropion for treatment of amphetamine-type stimulant use disorder: A systematic review and meta-analysis of placebo-controlled randomized clinical trials
Another combination gaining attention is dextromethorphan-bupropion (branded as Auvelity), where bupropion serves double duty: it has its own antidepressant action and it inhibits CYP2D6, which slows the breakdown of dextromethorphan and allows it to reach therapeutic levels as a glutamate modulator.22PubMed Central. Dextromethorphan-bupropion combination in depression with dual diagnosis: Insights from a case series This is one of the few genuinely new antidepressant mechanisms approved in recent years.
Pregnancy Considerations
For pregnant people who need to stay on an antidepressant, bupropion’s safety profile is cautiously reassuring but not entirely settled. A large epidemiological study found that the overall rate of congenital malformations after first-trimester bupropion exposure was about 23 per 1,000 infants, which was virtually identical to the rate seen with other antidepressants and with bupropion used outside the first trimester. The authors concluded that the data did not support a teratogenic effect.23PubMed. Bupropion in pregnancy and the prevalence of congenital malformations
However, one case-control study identified a possible link between early-pregnancy bupropion use and a specific type of heart defect involving the left outflow tract, with an adjusted odds ratio of about 2.6. The researchers described the absolute risk increase as small and called for further studies to confirm the finding.24American Journal of Obstetrics and Gynecology. Maternal use of bupropion and risk for congenital heart defects A broader review concluded that bupropion used as an antidepressant does not appear to increase the overall rate of congenital anomalies, and that concentrations in breast milk are low enough that breastfeeding is not considered a safety concern.25PubMed. Pharmacological Treatment of Attention Deficit Hyperactivity Disorder During Pregnancy and Lactation The decision to continue or start bupropion during pregnancy is nuanced, and the risk of untreated depression itself has to be weighed against any theoretical medication risk.
Kidney Disease and Dose Adjustments
Bupropion is extensively metabolized by the liver, and its metabolites are cleared by the kidneys. In people with impaired kidney function, the parent drug’s blood levels roughly doubled, and its half-life more than doubled as well.26PubMed Central. Effect of renal impairment on the pharmacokinetics of bupropion and its metabolites Active metabolites also accumulate significantly. A pharmacokinetic study in hemodialysis patients suggested that a dose of 150 mg every three days may be more appropriate than the manufacturer’s recommendation of 150 mg daily for renal impairment, because dialysis does not effectively clear the main metabolite.27Nephron Clinical Practice. Pharmacokinetics of Bupropion and Its Metabolites in Haemodialysis Patients Who Smoke: A Single Dose Study If you have significant kidney disease, your prescriber should use a reduced dose and monitor for side effects more closely.
Stopping Bupropion
Bupropion is generally considered to have a lower risk of discontinuation symptoms than SSRIs or SNRIs, but “lower risk” does not mean “zero risk.” Case reports have documented irritability, anxiety, insomnia, headache, and body aches after abrupt discontinuation.28PubMed Central. Bupropion-Associated Withdrawal Symptoms: A Case Report Most clinicians recommend a gradual taper over a couple of weeks rather than stopping cold turkey, especially if you have been taking it for several months or longer. If you are on 150 mg twice daily, a typical taper might involve dropping to once daily for a week or two before stopping.
Misuse and Abuse Potential
Bupropion is not a controlled substance, and in standard oral doses its abuse potential is low. But it has become a recognized drug of misuse, particularly in correctional settings where access to traditional stimulants is restricted. When tablets are crushed and snorted, the drug hits the brain much faster than it was designed to, producing a brief stimulant-like high with euphoria and increased energy.29PubMed. Bupropion diversion and misuse in the correctional facility The risk of seizures increases sharply with this route of administration because the sustained-release coating is destroyed, delivering the full dose at once. Fatal outcomes have been reported after nasal insufflation of large quantities.30PubMed Central. Bupropion Misuse by Nasal Insufflation with a Fatal Outcome: Case Report and Review This issue has led some correctional pharmacies to restrict or closely monitor bupropion dispensing, and it is worth being aware of if you are prescribing or receiving this medication in institutional settings.