Too many care homes are still using a "chemical cosh" to quieten dementia patients despite a Government-ordered review of their use, research suggests.
The study from five universities found no overall reduction in the prescribing of antipsychotics to dementia patients in UK care homes between 2009 and 2012.
In most (77%) cases in 2012, treatment was "excessive" and lasted for far longer than the recommended six weeks.
Older antipsychotics such as haloperidol and chlorpromazine are also still being used extensively, the study found - with no significant shift towards newer, safer types such as risperidone.
Antipsychotics were originally developed for patients with schizophrenia or psychosis. However, they are regularly prescribed "off label" for people with dementia, some of whom show challenging behaviour.
The new research comes despite the Government's 2009 National Dementia Strategy, which called for a review of the use of antipsychotics in light of their side-effects, which include strokes.
In 2014, Health Secretary Jeremy Hunt said the attitude towards dementia "must and will change" as he recounted reports of people "drugged up with a chemical cosh just so a care assistant can get a good night's sleep".
In the latest study, led by Coventry University and published in the journal BMJ Open, experts examined prescribing data from more than 600 care homes and found no significant decline in antipsychotic prescribing rates over the period.
Care homes in the top fifth for prescribing were more likely to be in deprived areas, the study found, while there was a six-fold variation in prescribing rates depending on geographical area.
George McNamara, head of policy at Alzheimer's Society, said: "This continued reliance on antipsychotics to manage behavioural symptoms of dementia is deeply worrying.
"Around 90% of people with dementia experience symptoms that affect their behaviour causing aggression, agitation, or even delusions and hallucinations. These symptoms can develop as part of their condition, but may also be caused by other factors - pain, discomfort, or unmet need.
"When this is the case, prescribing antipsychotics treats the person with dementia as the problem rather than the root cause of their behaviour.
"Antipsychotics increase the risk of stroke, falls and even death - it's shocking that the evidence continues to be flatly ignored. With person-centred approaches and training programmes for care home staff, continued inappropriate prescribing is a step backward into the dark ages."
Professor Clive Bowman, from City, University of London - which took part in the latest research, said: "Our study shows that the National Dementia Strategy has failed to have a sustained effect on the excessive prescription of antipsychotic medicines for people resident in care homes.
"This is unacceptable. Clear standards are required regarding the use of these drugs and a designated responsibility for monitoring medicines and their usage mandated."
Research from the King's Fund has found that cluttered ward layouts and poor signage in hospitals and care homes are the top causes of confusion and distress in people with dementia.
In the latest study, the researchers found that almost a fifth of care home residents were prescribed at least one antipsychotic at the start of the study. The figure was similar by the end of the study.