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Side Effects


The following adverse reactions are discussed in greater detail in other sections of the labeling:

Clinical Trials Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared with rates in the clinical trials of another drug and may not reflect the rates observed in clinical practice.

Adverse Reactions Leading To Discontinuation Of Treatment

Adverse reactions were sufficiently troublesome to cause discontinuation of treatment in 8% of the 706 subjects treated with ZYBAN and 5% of the 313 patients treated with placebo. The more common events leading to discontinuation of treatment with ZYBAN included nervous system disturbances (3.4%), primarily tremors, and skin disorders (2.4%), primarily rashes.

Commonly Observed Adverse Reactions

The most commonly observed adverse reactions consistently associated with the use of ZYBAN were dry mouth and insomnia. The incidence of dry mouth and insomnia may be related to the dose of ZYBAN. The occurrence of these adverse reactions may be minimized by reducing the dose of ZYBAN. In addition, insomnia may be minimized by avoiding bedtime doses.

Adverse reactions reported in the dose-response and comparator trials are presented in Table 2 and Table 3, respectively. Reported adverse reactions were classified using a COSTART-based dictionary.

Table 2: Adverse Reactions Reported by at Least 1% of Subjects and at a Greater Frequency than Placebo in the Dose-Response Trial

Adverse Reaction ZYBAN 100 to 300 mg/day
(n = 461) %
(n = 150) %
Body (General)
  Neck pain 2 < 1
  Allergic reaction 1 0
  Hot flashes 1 0
  Hypertension 1 < 1
  Dry mouth 11 5
  Increased appetite 2 < 1
  Anorexia 1 < 1
  Arthralgia 4 3
  Myalgia 2 1
Nervous system
  Insomnia 31 21
  Dizziness 8 7
  Tremor 2 1
  Somnolence 2 1
  Thinking abnormality 1 0
  Bronchitis 2 0
  Pruritus 3 < 1
  Rash 3 < 1
  Dry skin 2 0
  Urticaria 1 0
Special senses
  Taste perversion 2 < 1

Table 3: Adverse Reactions Reported by at Least 1% of Subjects on Active Treatment and at a Greater Frequency than Placebo in the Comparator Trial

Adverse Experience (COSTART Term) ZYBAN 300 mg/day
(n = 243)%
Nicotine Transdermal System (NTS) 21 mg/day
(n = 243)%
(n = 244)%
(n = 159)%
  Abdominal pain 3 4 1 1
  Accidental injury 2 2 1 1
  Chest pain < 1 1 3 1
  Neck pain 2 1 < 1 0
  Facial edema < 1 0 1 0
  Hypertension 1 < 1 2 0
  Palpitations 2 0 1 0
  Nausea 9 7 11 4
  Dry mouth 10 4 9 4
  Constipation 8 4 9 3
  Diarrhea 4 4 3 1
  Anorexia 3 1 5 1
  Mouth ulcer 2 1 1 1
  Thirst < 1 < 1 2 0
  Myalgia 4 3 5 3
  Arthralgia 5 3 3 2
Nervous system
  Insomnia 40 28 45 18
  Dream abnormality 5 18 13 3
  Anxiety 8 6 9 6
  Disturbed concentration 9 3 9 4
  Dizziness 10 2 8 6
  Nervousness 4 < 1 2 2
  Tremor 1 < 1 2 0
  Dysphoria < 1 1 2 1
  Rhinitis 12 11 9 8
  Increased cough 3 5 < 1 1
  Pharyngitis 3 2 3 0
  Sinusitis 2 2 2 1
  Dyspnea 1 0 2 1
  Epistaxis 2 1 1 0
  Application site reactiona 11 17 15 7
  Rash 4 3 3 2
  Pruritus 3 1 5 1
  Urticaria 2 0 2 0
Special Senses
  Taste perversion 3 1 3 2
  Tinnitus 1 0 < 1 0
a Subjects randomized to ZYBAN or placebo received placebo patches.

Adverse reactions in a 1-year maintenance trial and a 12-week COPD trial with ZYBAN were quantitatively and qualitatively similar to those observed in the dose-response and comparator trials.

Other Adverse Reactions Observed During The Clinical Development Of Bupropion

In addition to the adverse reactions noted above, the following adverse reactions have been reported in clinical trials with the sustained-release formulation of bupropion in depressed subjects and in nondepressed smokers, as well as in clinical trials with the immediate-release formulation of bupropion.

Adverse reaction frequencies represent the proportion of subjects who experienced a treatment-emergent adverse reaction on at least one occasion in placebo-controlled trials for depression (n = 987) or smoking cessation (n = 1,013), or subjects who experienced an adverse reaction requiring discontinuation of treatment in an open-label surveillance trial with bupropion sustained-release tablets (n = 3,100). All treatment-emergent adverse reactions are included except those listed in Tables 2 and 3, those listed in other safety-related sections of the prescribing information, those subsumed under COSTART terms that are either overly general or excessively specific so as to be uninformative, those not reasonably associated with the use of the drug, and those that were not serious and occurred in fewer than 2 subjects.

Adverse reactions are further categorized by body system and listed in order of decreasing frequency according to the following definitions of frequency: Frequent adverse reactions are defined as those occurring in at least 1/100 subjects. Infrequent adverse reactions are those occurring in 1/100 to 1/1,000 subjects, while rare events are those occurring in less than 1/1,000 subjects.

Body (General): Frequent were asthenia, fever, and headache. Infrequent were chills, inguinal hernia, and photosensitivity. Rare was malaise.

Cardiovascular: Infrequent were flushing, migraine, postural hypotension, stroke, tachycardia, and vasodilation. Rare was syncope.

Digestive: Frequent were dyspepsia and vomiting. Infrequent were abnormal liver function, bruxism, dysphagia, gastric reflux, gingivitis, jaundice, and stomatitis.

Hemic and Lymphatic: Infrequent was ecchymosis.

Metabolic and Nutritional: Infrequent were edema and peripheral edema.

Musculoskeletal: Infrequent were leg cramps and twitching.

Nervous System: Frequent were agitation, depression, and irritability. Infrequent were abnormal coordination, CNS stimulation, confusion, decreased libido, decreased memory, depersonalization, emotional lability, hostility, hyperkinesia, hypertonia, hypesthesia, paresthesia, suicidal ideation, and vertigo. Rare were amnesia, ataxia, derealization, and hypomania.

Respiratory: Rare was bronchospasm.

Skin: Frequent was sweating.

Special Senses: Frequent was blurred vision or diplopia. Infrequent were accommodation abnormality and dry eye.

Urogenital: Frequent was urinary frequency. Infrequent were impotence, polyuria, and urinary urgency.

Postmarketing Experience

The following adverse reactions have been identified during post-approval use of ZYBAN and are not described elsewhere in the label. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a relationship to drug exposure.

Body (General)

Arthralgia, myalgia, and fever with rash and other symptoms suggestive of delayed hypersensitivity. These symptoms may resemble serum sickness [see WARNINGS AND PRECAUTIONS].


Cardiovascular disorder, complete AV block, extrasystoles, hypotension, myocardial infarction, phlebitis, and pulmonary embolism.


Colitis, esophagitis, gastrointestinal hemorrhage, gum hemorrhage, hepatitis, increased salivation, intestinal perforation, liver damage, pancreatitis, stomach ulcer, and stool abnormality.


Hyperglycemia, hypoglycemia, and syndrome of inappropriate antidiuretic hormone.

Hemic And Lymphatic

Anemia, leukocytosis, leukopenia, lymphadenopathy, pancytopenia, and thrombocytopenia. Altered PT and/or INR, infrequently associated with hemorrhagic or thrombotic complications, were observed when bupropion was coadministered with warfarin.

Metabolic And Nutritional



Arthritis and muscle rigidity/fever/rhabdomyolysis, and muscle weakness.

Nervous System

Abnormal electroencephalogram (EEG), aggression, akinesia, aphasia, coma, completed suicide, delirium, delusions, dysarthria, euphoria, extrapyramidal syndrome (dyskinesia, dystonia, hypokinesia, parkinsonism), hallucinations, increased libido, manic reaction, neuralgia, neuropathy, paranoid ideation, restlessness, suicide attempt, and unmasking tardive dyskinesia.




Alopecia, angioedema, exfoliative dermatitis, hirsutism, and Stevens-Johnson syndrome.

Special Senses

Deafness, increased intraocular pressure, and mydriasis.


Abnormal ejaculation, cystitis, dyspareunia, dysuria, gynecomastia, menopause, painful erection, prostate disorder, salpingitis, urinary incontinence, urinary retention, urinary tract disorder, and vaginitis.

Read the Zyban (bupropion hcl) Side Effects Center for a complete guide to possible side effects


Potential For Other Drugs To Affect ZYBAN

Bupropion is primarily metabolized to hydroxybupropion by CYP2B6. Therefore, the potential exists for drug interactions between ZYBAN and drugs that are inhibitors or inducers of CYP2B6.

Inhibitors Of CYP2B6

Ticlopidine and Clopidogrel: Concomitant treatment with these drugs can increase bupropion exposure but decrease hydroxybupropion exposure. Based on clinical response, dosage adjustment of ZYBAN may be necessary when coadministered with CYP2B6 inhibitors (e.g., ticlopidine or clopidogrel) [see CLINICAL PHARMACOLOGY].

Inducers Of CYP2B6

Ritonavir, Lopinavir, and Efavirenz: Concomitant treatment with these drugs can decrease bupropion and hydroxybupropion exposure. Dosage increase of ZYBAN may be necessary when coadministered with ritonavir, lopinavir, or efavirenz [see CLINICAL PHARMACOLOGY] but should not exceed the maximum recommended dose.

Carbamazepine, Phenobarbital, Phenytoin: While not systematically studied, these drugs may induce the metabolism of bupropion and may decrease bupropion exposure [see CLINICAL PHARMACOLOGY]. If bupropion is used concomitantly with a CYP inducer, it may be necessary to increase the dose of bupropion, but the maximum recommended dose should not be exceeded.

Potential For ZYBAN To Affect Other Drugs

Drugs Metabolized By CYP2D6

Bupropion and its metabolites (erythrohydrobupropion, threohydrobupropion, hydroxybupropion) are CYP2D6 inhibitors. Therefore, coadministration of ZYBAN with drugs that are metabolized by CYP2D6 can increase the exposures of drugs that are substrates of CYP2D6. Such drugs include certain antidepressants (e.g., venlafaxine, nortriptyline, imipramine, desipramine, paroxetine, fluoxetine, and sertraline), antipsychotics (e.g., haloperidol, risperidone, thioridazine), beta-blockers (e.g., metoprolol), and Type 1C antiarrhythmics (e.g., propafenone and flecainide). When used concomitantly with ZYBAN, it may be necessary to decrease the dose of these CYP2D6 substrates, particularly for drugs with a narrow therapeutic index.

Drugs that require metabolic activation by CYP2D6 to be effective (e.g., tamoxifen) theoretically could have reduced efficacy when administered concomitantly with inhibitors of CYP2D6 such as bupropion. Patients treated concomitantly with ZYBAN and such drugs may require increased doses of the drug [see CLINICAL PHARMACOLOGY].

Drugs That Lower Seizure Threshold

Use extreme caution when coadministering ZYBAN with other drugs that lower seizure threshold (e.g., other bupropion products, antipsychotics, antidepressants, theophylline, or systemic corticosteroids). Use low initial doses and increase the dose gradually [see CONTRAINDICATIONS, WARNINGS AND PRECAUTIONS].

Dopaminergic Drugs (Levodopa And Amantadine)

Bupropion, levodopa, and amantadine have dopamine agonist effects. CNS toxicity has been reported when bupropion was coadministered with levodopa or amantadine. Adverse reactions have included restlessness, agitation, tremor, ataxia, gait disturbance, vertigo, and dizziness. It is presumed that the toxicity results from cumulative dopamine agonist effects. Use caution when administering ZYBAN concomitantly with these drugs.

Use With Alcohol

In postmarketing experience, there have been rare reports of adverse neuropsychiatric events or reduced alcohol tolerance in patients who were drinking alcohol during treatment with ZYBAN. The consumption of alcohol during treatment with ZYBAN should be minimized or avoided.

MAO Inhibitors

Bupropion inhibits the reuptake of dopamine and norepinephrine. Concomitant use of MAOIs and bupropion is contraindicated because there is an increased risk of hypertensive reactions if bupropion is used concomitantly with MAOIs. Studies in animals demonstrate that the acute toxicity of bupropion is enhanced by the MAO inhibitor phenelzine. At least 14 days should elapse between discontinuation of an MAOI and initiation of treatment with ZYBAN. Conversely, at least 14 days should be allowed after stopping ZYBAN before starting an MAOI intended to treat psychiatric disorders [see DOSAGE AND ADMINISTRATION, CONTRAINDICATIONS].

Smoking Cessation

Physiological changes resulting from smoking cessation, with or without treatment with ZYBAN, may alter the pharmacokinetics or pharmacodynamics of certain drugs (e.g., theophylline, warfarin, insulin) for which dosage adjustment may be necessary.

Drug-Laboratory Test Interactions

False-positive urine immunoassay screening tests for amphetamines have been reported in patients taking bupropion. This is due to lack of specificity of some screening tests. Falsepositive test results may result even following discontinuation of bupropion therapy. Confirmatory tests, such as gas chromatography/mass spectrometry, will distinguish bupropion from amphetamines.

Read the Zyban Drug Interactions Center for a complete guide to possible interactions

This monograph has been modified to include the generic and brand name in many instances.

Last reviewed on RxList: 6/9/2016

Side Effects

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