A study suggests that prescribing errors in NHS hospitals could be putting patients at risk.

BBC News Online examines the issue and what is being done to protect patients.

How bad is the situation in the UK?

There is little data on how many patients are being put at risk because of prescribing errors.

This latest study at a major London hospital identified 135 errors a week. Mistakes were made in 1.5% of drug orders. One in four of these were "potentially serious".

Some of these incidents involved powerful drugs which if given in the wrong dose could potentially have killed patients. Why is the latest report so significant?

This is one of the first studies to look at prescribing errors in hospitals.

It suggests that many of the mistakes are being made by doctors in training.

The report indicates that current procedures for ensuring patients are protected need to be strengthened.

This includes telling the entire medical team when an error has been made so the can learn from their mistakes.

The government has pledged to cut prescribing errors by 40% by 2005.

Should patients be worried?

The study is limited in that it only looked at a single hospital over the course of four weeks in 1999.

There is no data on the overall situation throughout the NHS.

However, the researchers believe that little has changed and that mistakes could still be happening.

What is being done to protect patients?

In recent years, hospital pharmacists have been given a greater role in managing the drug treatment given to patients.

Some hospitals have introduced a computer-based system which can identify potential errors early.

The National Patients Safety Agency is also hoping to improve the situation.

It is establishing a new confidential reporting system which will monitor mistakes such as these so that lessons can be learnt at local and national level

It is also hoping to spot trends - common errors which keep happening again and again - and try to work out ways to prevent them.