A BMJ study of nearly one million UK patients has found that around one in 20 triggered indicators for unsafe prescribing in general practice.
Nearly double that number triggered indicators for inadequate monitoring.
Researchers from the University of Manchester studied the health records for 949,552 adult patients in 526 general practices who were potentially at risk of prescribing or monitoring errors. They focused on prescriptions of anticoagulants, anti-platelets, NSAIDs, β blockers, glitazones, metformin, digoxin, antipsychotics, combined hormonal contraceptives and oestrogens. The study also considered potentially inadequate monitoring by blood test of patients with repeat prescriptions of angiotensin converting enzyme inhibitors and loop diuretics, amiodarone, methotrexate, lithium or warfarin.
They found that 5.26 per cent of patients triggered at least one prescribing indicator and 11.8 per cent triggered at least one monitoring indicator. The prevalence of different types of potentially hazardous prescribing ranged from almost zero to 10.2 per cent, and for inadequate monitoring the range was 10.4 to 41.9 per cent.
Older patients and those prescribed multiple repeat medications had significantly higher risks of triggering a prescribing indicator whereas younger patients with fewer repeat prescriptions had a significantly higher risk of triggering a monitoring indicator. High variation was found between practices for some indicators.
The researchers make the point that prescribing safety indicators describe patterns that can increase the risk of harm to the patient and should generally be avoided but there will "always be exceptions where the indicator is clinically justified".
Other studies have found that adverse drug events account for around 7 per cent of hospital admissions in the UK with half of these judged to be preventable. A 2012 study found that one in 20 prescription items was associated with a clinically important error and one in 550 was associated with a serious error.
Dr Maureen Baker, Chair of the Royal College of GPs, commented on the study: "Increasingly, we need more effective ways of looking after – often elderly - people with multiple conditions so that we achieve the right balance between making sure patients have the medications needed for the best possible quality of life, without running into problems from side-effects and interactions from multiple medications.
"We hope that College-led initiatives, such as having pharmacists working as part of the practice team, will help practices to manage medications most effectively."