New Zealand's high rate of antidepressant prescriptions is being boosted by people using the drugs to help them quit smoking.

The trend became clear after the release last week of new smoking cessation guidelines. Health Ministry figures show antidepressant use has nearly doubled in the past decade, with almost two million prescriptions written for the drugs each year.

Now the guidelines, produced by Auckland University's Clinical Trials Research Unit, show that two antidepressants - nortriptyline (marketed here as Aventyl) and bupropion (Zyban) - have proved to be as, or more, effective as nicotine replacement therapy, and thousands of smokers are taking them.

More than 62,000 prescriptions for nortriptyline, a Government subsidised drug, were written last year.

Nortriptyline is recorded by the Government drug funding agency Pharmac in its expenditure as an antidepressant.

Ben Youdan, director of anti-smoking lobby group ASH, said bupropian - the fourth most prescribed "anti-depressant" in the United States last year - and nortriptyline, were now primarily used as stop- smoking treatments.

Dr Chris Bullen, a co-author of the guidelines, said there was no information available to show what bupropian and nortriptyline were specifically prescribed for.

Butt out

* Of the 23 per cent of New Zealanders who smoke, a third have tried at least once to quit over the last year. A quarter of this group used aids: Zyban, 7 per cent; nicotine gum, 35 per cent; patches, 68 per cent.

* Smoking is the single greatest cause of premature death in New Zealand. It is directly linked to 5000 deaths each year.

* Half of all continuing smokers will die from smoking an average 14 years early.

Comment: So the propaganda says.

* New Zealand is one of only a few countries offering Government-funded nicotine replacement therapy.