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GPs have been urged to be more aggressive in using multiple drug therapies for diabetes after researchers identified a group of patients who were highly resistant to treatment.
Their study of 70,000 UK patients found those with elevated initial blood sugar were unlikely to respond to single drug therapy, however high the dose.
Only 44 per cent of patients with an initial HbA1c over 9.5 per cent were controlled below 7.5 per cent by metformin or sulphonylurea alone, according to the study.
Among patients with an initial HbA1c below 9.5 per cent, 68 per cent of patients were controlled by single drugs.
Diabetes experts said the results suggested patients were less responsive to single drug therapy than had been thought and needed to be moved more quickly to multiple drugs.
Researchers analysed treatment data from 243 general practices. They found increasing the dose of metformin from 500mg per day to 1,500mg per day reduced average HbA1c by 0.5 per cent, but even high doses left many patients uncontrolled.
Study leader Dr Mel Calvert, researcher at the department of primary care and general practice at the University of Birmingham, said many patients would benefit from the earlier addition of a second therapy.
Dr Calvert, who will present the results at the Diabetes UK's annual conference in Glasgow next week, said: 'Our study has shown many patients on a single oral agent remain uncontrolled for long periods of time. Many of these patients would benefit from a second therapy, started earlier than observed in our study.'
She added: 'A substantial proportion will remain uncontrolled after addition of a second therapy and additional treatment options should be considered sooner for these patients.'
Dr Peter Tasker, a GP in Kings Lynn and former head of Primary Care Diabetes UK, said the results suggested patients could not be managed on lifestyle advice or a single glycaemic control agent alone for as long as had been thought. 'I feel this step-wise pathway needs to be concertinaed down,' he said.
By Cato Pedder