More than four out of 10 PCTs have introduced 28-day prescribing limits without any assessment of their impact on patient care, GP can reveal.
But patient groups say the policies, designed to cut medicines wastage, will undermine access to treatment and increase costs and inconvenience for patients.
Of 46 PCTs who responded to a Freedom of Information request, 45 per cent had issued guidance for GPs to limit prescriptions to 28 days' supply.
Only one PCT had assessed how the guidance had affected the number of prescriptions patients collected from pharmacies or the number of prescriptions issued by doctors.
Only two PCTs assessed the extra administrative burden the guidance placed on practices.
The picture is similar for other measures introduced by trusts to tackle medicines wastage. For instance, 87 per cent have run initiatives to reduce medicines wastage in the past five years, but only 11 per cent collected information on their impact on patient care, cost or inconvenience to patients.
Edwina Wooler, clinical lead at Asthma UK, warned that people with long-term conditions could be particularly affected.
'This limit may result in patients paying more for the same amount of medicine, because they would have to pay a charge every time they renew their prescription,' she said.
Increased cost and extra trips to collect medicines could deter people from taking them as prescribed, Ms Wooler warned. She urged the DoH to carry out an impact assessment.
Roger Goss, co-director of Patient Concern, said PCTs should not put cost savings ahead of patient welfare. 'Many people on medicines long-term have mobility problems, or are living alone,' he said. 'How are they supposed to collect prescriptions every four weeks?'
Buckinghamshire GP Andrew Webber said he had asked his PCT what evidence there was that its 28-day prescribing policy would save money.
'The only evidence was one poorly researched paper,' he said. 'It might all blow up in our faces if PCTs across the country are pushing for 28-day scrips with no evidence.'
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