Arthur Trueman, 91, was diagnosed with dementia about four years ago and now lives in a care home.
After a relative of another resident complained that he had been verbally aggressive, a GP doubled the dose of an anti-psychotic drug Arthur had previously been taking. This was done over the phone.
Anti-psychotic drugs are used to calm agitated or aggressive behaviour - however they also have known side effects.
Arthur's son Allan says his father became "a completely different person" - less cooperative, increasingly incoherent and he refused to get out of bed.
Allan decided to take his father off the drugs and three days later Arthur was back to his old self.
Allan believes people with dementia should be given more mental simulation rather than turning to a "chemical cosh".
An official review, led by King's College London expert Professor Sube Banerjee, suggests needless use of anti-psychotic drugs is widespread in dementia care and contributes to the death of many patients.