About Zyban(Bupropion)

Bupropion (INN; also amfebutamone, brand names Wellbutrin, Zyban, Budeprion and Buproban) is an atypical antidepressant, which acts as a norepinephrine reuptake inhibitor and dopamine reuptake inhibitor, and a nicotinic antagonist. Bupropion belongs to the chemical class of aminoketones and is similar in structure to stimulant cathinone, anorectic diethylpropion and to phenethylamines in general. Bupropion is primarily used as an antidepressant and as a smoking cessation aid. In 2006 it was the fourth most prescribed antidepressant on the U.S. retail market with 21,141,000 prescriptions.

Side effects

For Bupropion SR (300 mg/day) common side effects with the greatest difference from placebo are dry mouth (17% vs 7% for placebo), nausea (13% vs 8% for placebo), insomnia (11% vs 6% for placebo), tremor (6% vs 1% for placebo), excessive sweating (6% vs 2% for placebo) and tinnitus (6% vs 2% for placebo). The two side effects which most often resulted in interruption of the treatment in the same trial were rash (2.4%) and nausea (0.8%). (The development of mild to moderate skin rashes is associated with sensitivity to dye components within the pill coating. This can often be alleviated by simply prescribing a different color pill.)

Seizure is the most controversial side effect of bupropion, which caused its temporary withdrawal (see History). The risk of seizure is highly dose-dependent: 0.1% at 100-300 mg of bupropion, 0.4% at 300-450 mg, and 2% at 600 mg. For comparison, the incidence of first unprovoked seizure in general population is 0.07-0.09%; the risk of seizure for other antidepressants is as follows: imipramine 0.1-0.6% depending on dosage, amitriptiline 0-0.06% depending on dosage, clomipramine 0.5%, maprotiline 0.4%, fluoxetine and fluvoxamine 0.2%. Experiments on mice indicate that increased susceptibility to seizure is a general side effect of antidepressants inhibiting norepinephrine transporter, such as imipramine, desipramine and reboxetine, given chronically. On the other hand, depression was reported to increase occurrence of seizures 2-7 fold as compared to the general population. In this light, the above statistics could indicate that low to moderate doses of antidepressants, including bupropion, may actually have an anti-convulsive action. Nevertheless, patients using bupropion should still be screened for pre-disposing factors that could contribute to and/or indicate a low seizure threshold. A prescriber may also review all other medications/substances the patient is using and make dosing decisions based on the results.

Three cases of liver toxicity of bupropion have been reported in the literature. This is extremely rare considering the widespread use of the drug.

The prescribing information notes that hypertension, sometimes severe, was observed in some patients, both with and without pre-existing hypertension, treated with bupropion. At the same time, the frequency of this side effect was under 1% and not significantly higher than for placebo. In a group of cardiac patients with depression, high doses of bupropion (400-500 mg/day) caused a rise of supine blood pressure but no effect on pulse rate. No statistically significant changes in blood pressure or heart rate occurred in patients both with and without heart conditions at a lower dose (300 mg/day) . In a study of bupropion for ADHD, a rise of systolic blood pressure by 6 mm Hg and heartbeat rate by 7 bits per minute (both statistically significant) was observed. A study of smokers hospitalized for heart disease found a 1.5-fold increase (close to being statistically significant) in the subsequent cardiovascular events in bupropion group as compared to the placebo group but no difference in blood pressure. Although cardiovascular side effects of bupropion appear to be mild, it can not be recommended for patients with heart disease since the safety comparison with SSRI antidepressants (such as sertraline and fluoxetine which may have a preventative effect after a myocardial infarction) is not in its favor.

A single case of clitoral priapism (clitorism) was reported in the literature.

In the UK, more than 7,600 reports of suspected adverse reactions were collected in the first two years after bupropion's approval by MHRA as a part of the Yellow Card Scheme which monitored side effects. Approximately 540,000 people were treated by bupropion for smoking cessation during that period. 60 reports of "suspected (emphasis by MHRA) adverse reactions to Zyban which had a fatal outcome" were received. The agency concluded that "in the majority of cases the individual's underlying condition may provide an alternative explanation." This is consistent with a large (9300 patients) safety study, which indicated that mortality of smokers taking bupropion is not higher than natural mortality of smokers of the same age.

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