Painkillers which are routinely given to dementia patients can triple the chance of suffering harmful side effects and personality changes, research suggests.

The study involving UK scientists found more than half of those given the drugs suffered adverse effects, with many increasingly confused and sedated by drugs which were supposed to treat pain.

Up to 40 per cent of dementia patients living in care homes are given opioid-based painkillers, such as the drug buprenorphine.

Researchers said the use of such pills was "doing more harm than good", calling for an urgent review of their use.