Pharmacotherapy of dementia with Lewy bodies.

The syndrome of dementia with Lewy bodies (DLB) is characterised by the clinical triad of fluctuating cognitive impairment, recurrent visual hallucinations and spontaneous motor features of Parkinsonism. In an attempt to define DLB as a distinct clinical syndrome separate from Alzheimer's disease (AD) and Parkinson's disease (PD) with dementia, a consensus workshop in 1995 established a new set of diagnostic criteria. Dementia that precedes or accompanies the onset of spontaneous (i.e., not neuroleptic-induced) Parkinsonism is termed DLB. In addition, fluctuations in alertness, cognition and function and visual hallucinations are emphasised and included as core features of DLB. The degree to which an individual patient exhibits cognitive impairment, behavioural problems and Parkinsonian features is variable. Therefore, treatment must be individualised. Although there are no officially approved drugs for DLB, limited experience from clinical trials, as well as past experience with the treatment of AD and PD patients, provide some basis for making drug choices. The cholinergic deficit seen in DLB makes cholinesterase inhibitor drugs the mainstay of treatment for cognitive impairment. This class of drugs has also shown therapeutic benefit in reducing hallucinations and other neuropsychiatric symptoms of the disease. Because of their relatively greater therapeutic window, cholinesterase inhibitors are also used as first-line therapy for the treatment of psychosis in DLB. Patients with DLB are extremely sensitive to the extrapyramidal side effects of neuroleptic medications. Thus, only atypical antipsychotic agents such as quetiapine, should be considered as alternative treatment for psychosis. Anxiety and depression are best treated with selective serotonin re-uptake inhibitors, whereas REM sleep behaviour disorder may be treated with low dose clonazepam. Parkinsonism responds to dopaminergic agents; however, precipitation or aggravation of hallucinosis may occur. Levodopa is preferred over dopamine agonists due to its lower propensity to cause hallucinations and somnolence. As the diagnostic criteria for DLB become more refined and validated by postmortem studies, it is hoped that rigorous, well-designed trials will be performed, aimed at alleviating the primary target symptoms of dementia, psychosis and Parkinsonism.