Stop-smoking medication has side effects that are more dangerous than smoking.
Nicotine replacement therapy (NRT), available over-the-counter in many countries, is designed to alleviate symptoms of nicotine withdrawal [
36]. NRT does not mimic the effects of a cigarette, but delivers low-level doses of nicotine in a non-combustible form and at a slower rate, and as such has low abuse potential [
37]. NRT does not contain the over 4000 other chemicals present in tobacco smoke, of which 69 are known carcinogens [
38].
The safety and efficacy of NRT has been studied in clinical trials and real-world studies for over 30 years. A systematic review of clinical trials found that NRT is associated with minor adverse events, including insomnia (11.0%) and gastrointestinal complaints (10.8%), which may cause mild discomfort [
39]. The most serious adverse event reported with notable frequency was heart palpitations/chest pains (3%). Safety concerns have been expressed for people with pre-existing cardiovascular disease, but there is no evidence that NRT causes life-threatening complications (see also [
40]), and the benefits of smoking cessation exceed any risk [
41]. In addition, there is currently insufficient evidence for the safety or efficacy of NRT in pregnancy [
42].
Other common side effects of NRT are associated with the mode and site of administration (e.g. 0 skin irritation where the nicotine patch is placed, or mouth ulcers following use of orally-administered NRT). Such problems are generally mild and can be easily overcome by switching to a different form (e.g. from the patch to nicotine gum).
Two forms of prescription-only medication for smoking cessation, bupropion and varenicline [
43,
44], are associated with some additional safety concerns. Bupropion is associated with an increased risk of seizure, occurring in 0.1% of users [
43], and is consequently contraindicated in smokers with a seizure disorder. A 2011 meta-analysis reported an association between varenicline use and increased cardiovascular events [
45], leading the US Food and Drug Administration (FDA) to issue a warning that varenicline might increase the risk of cardiovascular events in patients with cardiovascular disease [
46]. However, this review has been criticised for inappropriately excluding trials with no reported adverse events, among other methodological issues. A more recent review found no significant increase in serious cardiovascular adverse effects associated with varenicline use, either during treatment or for 30 days post-treatment [
47].
Concerns have also arisen about the potential of bupropion and varenicline to exacerbate neuropsychiatric symptoms. A full discussion of this issue is beyond the scope of this article, but the FDA currently recommends that both medications be used with caution by individuals with a history of psychiatric illness [
46].