Smokers would have a better chance of quitting the habit if they use nicotine gum and patches at the same time, rather than just one or the other.

A new systemic review, co-authored by a University of Auckland researcher, also found starting nicotine replacement therapy (NRT) a week or two before trying to quit smoking could also help – although more evidence was needed.

NRT is available as long-acting skin patches, and short-acting chewing gum, nasal and oral sprays, inhalers, lozenges and tablets that deliver nicotine through the body to the brain.

In New Zealand and many other countries, people can get NRT from healthcare professionals as well as over-the-counter, without prescriptions.

Advertisement

The aim of NRT was to replace the nicotine that people who smoke usually get from cigarettes, so the urge to smoke was reduced and they can stop smoking altogether.

The new Cochrane review covered 63 clinical trials with a total of 41,509 participants, who typically smoked at least 15 cigarettes a day at the start of the study.

The review authors found that just over 17 per cent of people who combined a patch with another type of NRT were able to quit for six months or longer, compared with about 14 per cent of people who used a single type.

People were also more likely to successfully quit if they used higher dose nicotine gum, containing 4mg of nicotine, in comparison to lower dose nicotine gum, containing 2mg of nicotine.

Higher dose nicotine patches - containing 25mg or 21mg of nicotine - probably made it more likely that a person will quit smoking than lower dose nicotine patches containing 15mg or 14mg.

All studies were conducted in people who wanted to quit smoking, and most were conducted in adults.

People enrolled in the studies typically smoked at least 15 cigarettes a day at the start of the studies.

"The review shows a clear advantage of using a combination of a long-acting and short-acting NRT compared with single therapy alone," said Professor Chris Bullen, of the university's School of Population Health.

Advertisement

"Importantly, the Cochrane review found no evidence that using two NRT products together increases the risk of harms, which are rare and minor – such as skin irritation from patches, or mouth ulcers from lozenges."

Bullen said the guidelines in New Zealand lined up with these latest findings.

"But one potential barrier to smokers wanting to use combined NRT is that you have to pay a separate pharmacy dispensing fee for each type – that's something worth reviewing on the basis of this evidence.

"However, if people go to their local 'stop smoking' provider, they can get NRT products for free.

The review's lead author, Dr Nicola Lindson from the Nuffield Department of Primary Care Health Sciences at the University of Oxford in the UK, said the researchers tried to answer other important questions about NRT.

They included how long NRT should be used for, whether NRT should be used on a set schedule or as wanted, and whether more people stop smoking using NRT when it was provided for free, versus if they had to pay for it.

"However, more research is needed to answer these questions."