Texas-based cardiologist Dr Ramachandra Kolluru gave patient Ramon Vasquez what he said was a prescription for the angina drug Isordil.

However, because of the doctor's untidy writing, a pharmacist dispensed Plendil - a high blood pressure medication - instead.

In fact, the dose of Plendil was double the recommended maximum daily amount.

Mr Vasquez subsequently had a heart attack and died several days later. His family sued both the doctor and the pharmacist for negligence.

The jury in the case found both equally liable, awarding a total of $450,000 in damages.

Mr Vasquez's attorney, Kent Buckingham, said: "Many doctors are having to stop and think: 'By golly, that prescription I wrote illegibly this morning may result in an adverse verdict.'"

Computers reduce handwriting problem

The problem of illegible hand-written prescriptions has diminished in the UK over recent years, mainly due to the introduction computerised prescription-printing at many GP practices.

However, within hospitals, there is still a reliance on hand-written instructions in many cases.

Dr Rupert Lee, who works for the Medical Defence Union, which advises UK doctors how to avoid potentially dangerous situations, and represents them legally if claims arise, said that while uncommon, there was still the potential for mistakes of this kind.

He said: "It does happen from time to time - I'm not sure it's a significant problem, but we do come across cases where the prescription has been correct but the handwriting has let the doctor down."

However, he said that the move towards computerisation of prescribing had created its own difficulties.