CHICAGO (Reuters) – Smokers who wore nicotine patches for six months instead of the recommended two were more likely to quit smoking and had an easier time recovering from an occasional slip, US researchers said last week.

But the effect appeared to last only as long as the treatment, suggesting that smokers may need longer-term or even chronic treatment to stay smoke-free.

"This suggests that we may need to reconsider our guidelines about the length of treatment and consider, at least for some smokers, longer-term therapy," said Caryn Lerman of the University of Pennsylvania School of Medicine, whose study appears in the Annals of Internal Medicine.

Lerman said the team did the study because of the growing recognition that nicotine dependence is a condition characterised by many relapses.

To test this, she and colleagues set up a clinical trial of 568 people who smoked ten or more cigarettes per day for at least the past year. About half were given GlaxoSmithKline's Nicoderm CQ patch for eight weeks, followed by a dummy patch. The other half were on the patch for a full six months.

Neither the patients nor the doctors knew who was getting the active patch.

At the end of 24 weeks, smokers who were on extended patch treatment the whole time were twice as likely to have quit smoking as those who got a dummy patch after two months.

"We found that extending the duration of therapy to 24 weeks was significantly more effective in helping smokers quit compared to the standard duration of eight weeks," Lerman said.

However, after a year, there were no differences in the main measures of smoking in the extended patch or conventional patch groups.

But the researchers did notice that people who had been on the patch longer were more likely (29.1 percent vs. 21.3 percent) to have reported no periods of smoking lasting more than seven days in a row – during the entire year. The team said the results were comparable to those seen with drugs such as Glaxo's Zyban and Pfizer Inc's Chantix, drugs that have strong safety warnings on their labeling because that can cause depression, hostility and other behavioural changes. Lerman said the patch, by comparison, is safe and it may be more convenient because it can be purchased over-the-counter without a prescription.

The team is now studying just how long smokers might need to stay on the patch to overcome their smoking dependence, or whether they might fare better taking more than one treatment at a time.