Dementia with Lewy-bodies (DLB) and
Parkinson's disease dementia (PDD) are no rare causes of
dementia. Both have neuropathologically, clinically, and neurochemically much in common. In the course of both conditions frequently psychotic symptoms occur, often induced by antiparkinsonian medication. Treatment of psychotic features with conventional
antipsychotics is not tolerated in many cases. Therefore low-dose
clozapine treatment is acknowledged usual practise for
psychosis in
Parkinson's disease and a case report indicates efficacy for
psychosis in DLB, too. All other atypical
antipsychotics except
risperidone are not licensed for
dementia in Germany, but
risperidone is contraindicated in DLB due to manufacturer's notice and usually not well tolerated in DLB and
Parkinson's disease. Open trials indicate safety for treatment of
psychosis in DLB and PDD with
quetiapine. Randomized controlled trials indicate, that
quetiapine is less effective than
clozapine against psychotic symptoms in both conditions, although comparatively safe.
Cholinesterase inhibitors, especially
rivastigmine, are a therapeutic alternative for treating both psychotic and
cognitive symptoms in both conditions.
Parkinsonism in DLB-patients responds worse to
levodopa compared to patient with
Parkinson's disease.
Anticholinergic drugs often induce
delirium in demented patients and therefore should be avoided. The same problem is associated with
dopamine agonists in PDD and DLB.
Amantadine, a
NMDA-receptor antagonist like
memantine, potentially bears the same risk of worsening psychotic symptoms. The following preliminary recommendation for
drug treatment of PDD and DLB can be given: Stop all
anticholinergic medication and reduce
levodopa and other antiparkinsonian medication to the tolerated minimum.
Levodopa alone is preferred. Treat with
cholinesterase inhibitors to the maximum tolerated dose. If there is no adequate response regarding psychotic symptoms, add
quetiapine. If this approach fails, replace
quetiapine by low-dose
clozapine. If behavioural disturbances are due to depression, anxiety, or irritability, treatment with an
antidepressant, preferably
citalopram, is an option.