More than 10,000 Britons may be dying each year because of bad reactions to medication, a study suggests.
Some drugs can have serious side-effects
Researchers at the University of Liverpool assessed 18,820 people admitted to two hospitals in Merseyside between November 2001 and April 2002.
They found that one in 16 had been admitted because of an adverse reaction to drugs such as aspirin. Some 28 died.
Writing in the British Medical Journal, they said nationally the number of deaths could top 10,000 a year.
The vast majority of people on medication do not suffer side-effects.
Millions of people take medicines every year without experiencing any problems.
The researchers found that 1,225 people were admitted to these two hospitals over the six-month period because of an adverse drug reaction.
Many were taking aspirin or other painkillers, known as non-steroidal anti-inflammatory drugs.
Others were taking blood-thinning drugs like warfarin or diuretics to reduce the amount of water in the body.
The most common reaction to these drugs was internal bleeding in the stomach.
The researchers calculated that 0.15% of those admitted to these hospitals died as a result of an adverse drug reaction.
Figures from the Department of Health show that there were 3.8m hospital admissions in 2002.
The researchers used this figure to calculate that nationally 5,700 patients may be dying as a result of adverse drug reactions.
However, they said the figure may be even higher because it does not take into account those who die from adverse reactions to drugs they receive in hospital.
"The true rate of death taking into account all ADRs (adverse drug reactions) - those causing admission and those occurring while patients are in hospital - may therefore turn out to be greater than 10,000 a year," they wrote.
According to the researchers, 70% of these reactions could have been avoided.
They said doctors should carefully consider if patients need a particular drug or such a high dose before prescribing it for patients.
"Many may be prevented through simple improvements in prescribing," they wrote.
"Simple measures such as regular review of prescriptions, the use of computerised prescribing and the involvement of pharmacists in assessing prescribing behaviour may all reduce the burden caused by ADRs (adverse drug reactions)."
The researchers estimated that adverse drug reactions cost the NHS around £466m a year.
"Measures are urgently needed to reduce the burden on the NHS," they said.
Measures in place
The Department of Health said measures were in place to identify and learn from adverse drug reactions.
Much of this work is done by the Medicines and Healthcare products Regulatory Agency.
"The safety of drugs is continuously monitored by the medicines watchdog, the MHRA, and they investigate all and any new safety issues that emerge," a Department of Health spokeswoman said.
"We are continuously looking to make improvements, including introducing an online yellow card and modernising the way that reactions are reported."
The National Patients Safety Agency welcomed the study.
"It is worth highlighting to patients and their carers that every day more than a million people are treated safely in the NHS," it said in a statement.
"The NPSA is here to help make sure that when things go wrong, we find ways to prevent errors recurring."
David Pruce of the Royal Pharmaceutical Society of Great Britain described the findings as worrying.
He added: "Making better use of pharmacists in both assessing prescribing behaviour and in preventing individual adverse drug reactions is important."
Liberal Democrat health spokesman Paul Burstow said: "The Government should consider a mandatory report scheme so that NHS staff report all suspected reactions, not just on a voluntary basis."