Two key drugs recommended in international guidelines and used to treat alcoholic hepatitis are failing to increase patients' survival and leave death rates among patients "alarmingly high", researchers said on Wednesday.

In a trial involving more than 1,000 patients, the generic medicines -- prednisolone and pentoxifylline -- were found to make no significant reduction in death rates over 28 days, over 90 days, or even over a year.

Publishing their findings in the New England Journal of Medicine, scientists from Imperial College London said they highlighted an urgent need for more research into how to prevent and treat alcohol-related liver disease.

Drinking too much alcohol initially causes fat to build up in the liver - a potentially reversible condition. But alcoholic hepatitis -- caused by inflammation of the liver due to severe, alcohol-related liver disease -- is linked to liver failure and in up to 30 percent of cases it kills patients within a month.

In 2012 in England and Wales alone, alcoholic liver disease killed 4,425 people.

Mark Thursz, a professor in Imperial's department of medicine, said that while the drugs are widely used, but "the evidence supporting them comes from a few relatively small trials".

This latest study -- involving 1,053 patients being treated at 65 hospitals across Britain -- was four times larger than any previous trial in patients with severe alcoholic hepatitis, so gives a clearer picture of how effective the drugs are, he said.

In the study, the 1,053 were split into four groups, each receiving two treatments: prednisolone and pentoxifylline, prednisolone and placebo (or dummy pill), pentoxifylline and placebo, or two placebos.

Overall, 16 percent of patients died within 28 days of starting treatment. At 90 days, 29 percent of patients had died, and after a year, 56 percent had either died or had a liver transplant. There were no statistically significant differences in death rates between the groups.

"We were surprised to find neither treatment had a significant effect on survival after the first month, and the mortality rate after one year is alarmingly high," Thursz said.

He said one reason why the drugs might not improve survival rates was that they increase the risk of infection. Another is that many patients return to drinking, he said, leading to further hepatitis attacks or liver cirrhosis.