Antipsychotics in Alzheimer's disease: A critical analysis

The Influence of Selected Antipsychotic Drugs on Biochemical Aspects of Alzheimer's Disease

The aim of this study was to assess the potency of selected antipsychotic drugs (haloperidol (HAL), bromperidol (BRMP), benperidol (BNP), penfluridol (PNF), pimozide (PIM), quetiapine (QUET) and promazine (PROM)) on the main pathological hallmarks of Alzheimer's disease (AD). Binary mixtures of donepezil and antipsychotics produce an anti-BuChE effect, which was greater than either compound alone. The combination of rivastigmine and antipsychotic drugs (apart from PNF) enhanced AChE inhibition. The tested antipsychotics (excluding HAL and PNF) significantly reduce the early stage of Aβ aggregation. BRMP, PIM, QUET and PROM were found to substantially inhibit Aβ aggregation after a longer incubation time. A test of human erythrocytes hemolysis showed that short-term incubation of red blood cells (RBCs) with QUET resulted in decreased hemolysis. The antioxidative properties of antipsychotics were also proved in human umbilical vein endothelial cells (HUVEC); all tested drugs were found to significantly increase cell viability. In the case of astrocytes, BNP, PNF, PIM and PROM showed antioxidant potential.

Quetiapine and novel PDE10A inhibitors potentiate the anti-BuChE activity of donepezil

The symptoms of Alzheimer’s disease (AD) do not include only memory loss and cognitive decline but also neuropsychiatric manifestation. These AD-related symptoms are usually treated with the aid of antipsychotics; however, their effects on cognition and safety remain unexplored. The present study determines the effects of quetiapine, an atypical antipsychotic, and two imidazo[1,2-a]pyrimidine-based inhibitors of PDE10A on the activity of human cholinesterases. Quetiapine moderately inhibited BuChE (IC₅₀ = 6.08 ± 1.64 µmol/L) but improved the anti-BuChE properties of donepezil by decreasing its IC₅₀ value. Both PDE10A inhibitors were found to possess moderate anti-AChE properties. The combined mixtures of donepezil and imidazo[1,2-a]pyrimidine analogues produce a synergistic anti-BuChE effect which was greater than either compound alone, improving the IC₅₀ value by approximately six times. These favourable interactions between quetiapine, PDE10A inhibitors and clinically approved donepezil, resulting in improved anti-BuChE activity, can lead to a wider variety of potent AD treatment options.

Use and safety of antipsychotics in behavioral disorders in elderly people with dementia

In recent years, the use of antipsychotics has been widely debated for reasons concerning their safety in elderly patients affected with dementia. To update the use of antipsychotics in elderly demented people, a MEDLINE search was conducted using the following terms: elderly, conventional and atypical antipsychotics, adverse events, dementia, and behavioral and psychotic symptoms in dementia (BPSD). Owing to the large amounts of studies on antipsychotics, we mostly restricted the field of research to the last 10 years. Conventional antipsychotics have been widely used for BPSD; some studies showed they have an efficacy superior to placebo only at high doses, but they are associated with several and severe adverse effects. Atypical antipsychotics showed an efficacy superior to placebo in randomized studies in BPSD treatment, with a better tolerability profile versus conventional drugs. However, in 2002, trials with risperidone and olanzapine in elderly patients affected with dementia-related psychoses suggested the possible increase in cerebrovascular adverse events. Drug regulatory agencies issued specific recommendations for underlining that treatment of BPSD with atypical antipsychotics is "off-label." Conventional antipsychotics showed the same likelihood to increase the risk of death in the elderly as atypical agents, and they should not replace the atypical agents discontinued by Food and Drug Administration warnings. Before prescribing an antipsychotic drug, the following are factors to be seriously considered: the presence of cardiovascular diseases, QTc interval on electrocardiogram, electrolytic imbalances, familiar history for torsades des pointes, concomitant treatments, and use of drugs able to lengthen QTc. Use of antipsychotics in dementia needs a careful case-by-case assessment, together with the possible drug-drug, drug-disease, and drug-food interactions.