Fenoterol, the beta-agonist, has been confirmed as the cause of the epidemic of deaths among asthma sufferers in New Zealand.

The country's asthma death rate was the highest in the world for the decade that the drug was on the market. But the rate dropped dramatically in 1989 when the drug was withdrawn.

Dangers of the drug were first highlighted that year in a study published in The Lancet, but the findings were criticized even though similar conclusions were reached by other later studies.

Now the Wellington School of Medicine has analyzed the data and confirmed the original findings. They explain that New Zealand had the highest sales of the drug in the world; in most other countries, sales were low and the drug did not even receive a licence in the US.

When taken repeatedly, fenoterol has similar heart side effects to those noted with isoprenaline forte, the beta-agonist linked with high numbers of asthma deaths in Britain, Norway and Australasia in the 1960s.

When fenoterol was introduced in New Zealand in 1976, the death rate among asthma sufferers immediately rose dramatically and even after early warnings about all beta-agonists in 1981, the death rate among the five to 34 years age group remained the highest in the world, averaging 2.3 deaths per 100,000