An antibiotic used to treat a rare and deadly lung disease could be a lifesaver for adults with severe asthma, a ground-breaking Australian study has found.

Key points: Antibiotic azithromycin reduces asthma attacks in adult patients by over 40 per cent, research shows

Antibiotic azithromycin reduces asthma attacks in adult patients by over 40 per cent, research shows The drug appears to reduce inflammation in the small airways of the lungs

The drug appears to reduce inflammation in the small airways of the lungs The research team is working on an inhaler form of the drug to prevent antibiotic resistance

The research team from the Hunter Medical Research Institute (HMRI) in New South Wales gave the drug azithromycin to 200 patients whose asthma could not be fully controlled with traditional medication.

After taking the antibiotic three times a week for nearly a year, the patients reported a 40 per cent reduction in moderate and severe asthma attacks.

"Many of them were surprised by the benefit. One lady told me she'd never felt this good before, and she'd had asthma for many, many years," study author Professor Peter Gibson said.

Azithromycin is an antibiotic with anti-inflammatory properties that was hailed as a miracle cure in the 1980s for the lung disease diffuse panbronchiolitis.

"It's a very rare disease that kills people. It's rare in Australia but is quite common in Japan," Professor Gibson said.

"They discovered in the 1980s that if you treat these patients with azithromycin, they live. The patient had to take it for a year, but it kills the disease."

HMRI has found the drug also reduces swelling in the lungs of asthma sufferers.

"The main problem in asthma is narrowing of the airways, and that's caused by muscle spasms and inflammation. Azithromycin appears to work on the swelling and the mucus part of the problem," Professor Gibson said.

'I feel confident to do almost anything now'

Margaret Widders was initially sceptical when her doctor signed her up to the trial of azithromycin.

After taking azithromycin, Margaret Widders has halved her traditional doses of asthma medication. ( ABC News: Rebecca Armitage )

"About three weeks into the trial I could actually feel my symptoms becoming much less. I was quite surprised at that very quick response. I just felt so, so much better," she said.

The retired school teacher from Sydney has suffered from asthma since childhood, but in recent years she'd developed a persistent hacking cough that made exercise impossible.

"It was horrible to hear whenever I exerted myself, I would be coughing and it did restrict me. I had to sleep with a few pillows to reduce the coughing at night," she said.

After taking azithromycin for about a year, Mrs Widders' cough disappeared.

She no longer needs to take the antibiotic and has halved her traditional doses of asthma medication.

"I'm just so much more active. I walk up to 10 kilometres a day — quite challenging walks sometimes — and I feel fine," she said.

"I think it has improved me to that stage where I feel confident to do almost anything now."

Antibiotic resistance the next challenge for researchers

The HMRI team is now working on ways to prevent antibiotic resistance in patients who take azithromycin.

Professor Peter Gibson's team is working on an inhaler form of the drug. ( ABC News: Rebecca Armitage )

"It can be done. We must be selective about the people for whom the treatment is given, and also monitor the potential side effects of the treatment," Professor Gibson said.

"We think there could be opportunity to develop different ways to give this antibiotic, for example, in shorter periods. Perhaps having a drug holiday, giving it in even lower doses."

Professor Gibson is also working with his team on an inhaled version of the drug, which would remove the antibiotic but still deliver the anti-inflammatory to the patient's lungs.

The study has been published in the UK's Lancet Medical Journal.