Tens of thousands of Parkinson’s disease patients with a mixture of dementia and psychosis are being denied an effective drug that is available in the United States.
About 130,000 people in Britain have Parkinson’s, which erodes the brain’s control over body movements, leading to shaking and poor co-ordination.
In the long term, four out of five of these patients will also face mental decline when the disease spreads from the base of the brain to the areas that handle memory and planning.
As the condition worsens, three quarters of this group will also develop aspects of psychosis, such as paranoia, delusions or seeing, smelling or hearing things that are not really there.
Scientists in Britain have carried out a fresh analysis of the findings from their trial of a Parkinson’s medication and found that it is particularly potent in patients who have both dementia and psychosis.
The anti-psychotic pill, which is called pimavanserin but marketed in the US as Nuplazid, turned out to be twice as effective in those with severe cognitive impairment as in those without.
It was approved by the American Food and Drug Administration last year but has yet to be examined by regulators in Europe, who must approve the drug before the NHS can decide whether to offer it.
In the light of the new data, the charity Parkinson’s UK has called for pimavanserin to be made available in Britain to some 50,000 patients who would “benefit hugely” from it.
The neurologist Clive Ballard, who is executive dean of the University of Exeter’s medical school, said that Parkinson’s psychosis was a serious but largely neglected disorder that sometimes led patients to mistrust the carers and relatives who were trying to look after them.
“Visual hallucinations are the most common symptom,” he said. “They can be there for four hours a day or more. They can be very distressing. They are usually of people or animals.
“Other people start to develop delusional beliefs that there are intruders in the house or suspicious ideas that people are trying to harm them. Some might believe their husband or wife is there but is not really their husband or wife.”
Conventional psychosis drugs are dangerous for people with Parkinson’s as they block dopamine, the messenger chemical that the patients need to stay in charge of their own movements.
Pimavanserin instead locks down the activity of another signalling chemical, serotonin. Four years ago a trial of the drug in 199 patients showed that it worked about twice as well as a placebo at curbing the symptoms of psychosis.
Professor Ballard, who led the original study, said that the London-based European Medicines Agency should grant the drug conditional approval on the strength of his group’s new interpretation of the data, which is published in the journal Nature Reviews Neurology.
There are, however, outstanding questions about the treatment, which is sold by a company called Acadia Pharmaceuticals.
One is its cost, which at $28,000 a year in the US is higher than the price of other psychosis medicines. Another is its safety. One in 12 patients who received the drug in the trial had alarming side-effects such as irregular heartbeats or weight loss, compared with one in 20 in the placebo group.
The third is whether the treatment truly works as well as it is supposed to. Pimavanserin failed in two previous trials and succeeded in a third only after scientists devised a new scale for measuring the severity of Parkinson’s psychosis symptoms.
However, Claire Bale, of Parkinson’s UK, said it was high time the drug was made available in Europe. “This new analysis suggests that pimavanserin is even more effective for treating psychotic symptoms like hallucinations and delusions in people with Parkinson’s dementia than in those with Parkinson’s without dementia,” she said.
“Psychotic symptoms are a very common and distressing feature of Parkinson’s dementia and current treatment options are extremely limited. It is now imperative that pimavanserin goes through the European approval process . . . People with Parkinson’s can’t wait any longer for better treatments.”