Rationale: Oral nicotine dosing forms such as nicotine gum have been found to be effective in helping smokers to stop. Some, but not all studies have also found that they reduce the severity of withdrawal discomfort. With new oral nicotine products being developed and use of existing products widening, it is important to determine the strength of evidence that these forms of nicotine replacement reduce overall withdrawal discomfort and individual withdrawal symptoms including craving.
Objectives: To assess the strength of evidence that oral nicotine reduces the severity of overall withdrawal discomfort and individual withdrawal symptoms, including craving.
Methods: All published studies reporting effects of nicotine gum, inhaler, lozenge and sublingual tablet on recognised withdrawal symptoms were scanned and those that met a set of quality criteria were included in the review. The key characteristics of these studies were summarised and their findings tabulated.
Results: Of 27 studies that reported effects of oral nicotine products on at least one withdrawal symptom, 12 met the quality criteria (eight for nicotine gum, three for inhaler, one for microtab, none for 1 mg lozenge). Because of limitations on the reporting of the studies it was not possible to carry out meta-analyses and good data were available only for the first week of abstinence. Six out of seven studies reporting it found an effect on total withdrawal discomfort, nine out of nine found an effect on irritability, three out of four found an effect on anxiety and the only study that looked at it found an effect on depressed mood. Seven of 11 studies that looked at it found an effect on craving, but only three out of seven of the studies of nicotine gum. For other withdrawal symptoms the findings were more mixed.
Conclusions: We conclude that the strength of evidence that oral nicotine forms reduce total withdrawal discomfort, irritability and anxiety is high. There is some evidence for an effect on depressed mood and craving although in the latter case the evidence is less good for gum than other forms. Future studies of nicotine effects on withdrawal should meet minimum quality standards for design and reporting to enable results to be combined and compared across studies.