Introduction

Although nicotine replacement has been the first line drug treatment for smoking cessation for many years, other drugs of proved efficacy are also now available. Foremost among these is bupropion (marketed as Zyban). Bupropion was developed and initially introduced in the United States as an antidepressant but was subsequently noted to reduce the desire to smoke cigarettes and shown in clinical trials to be effective in smoking cessation.

Mechanism of action

Bupropion is an atypical antidepressant structurally similar to diethylpropion, an appetite suppressant. The mechanism of the antidepressant effect of bupropion is not fully understood, but bupropion inhibits reuptake of dopamine, noradrenaline, and serotonin in the central nervous system, is a non-competitive nicotine receptor antagonist, and at high concentrations inhibits the firing of noradrenergic neurons in the locus caeruleus.

It is not clear which of these effects accounts for the antismoking activity of the drug, but inhibition of the reductions in levels of dopamine and noradrenaline levels in the central nervous system that occur in nicotine withdrawal is likely to be important. The antismoking effect of bupropion does not seem to be related to the antidepressant effect as bupropion is equally effective as a smoking cessation therapy in smokers with and without depression.

Evidence for effectiveness

When given in association with intensive behavioural support, bupropion is as effective as nicotine replacement therapy (NRT), and like NRT, leads to a near doubling of the smoking cessation rate, achieving long term abstinence in 19% of smokers who use it to quit.

The effectiveness of bupropion in conjunction with less intensive levels of behavioural support has not been tested in …