title: Effects of combined MAO-B inhibitors and levodopa vs. monotherapy in Parkinson's disease.
abstract: BACKGROUND
  Prior studies report that monoamine oxidases inhibitors (MAO-I) when used as an adjunct to levodopa ameliorate motor symptoms in Parkinson's disease (PD), but this was not tested in relation to cognitive or psychiatric measures.
  
  
  OBJECTIVE
  Here, we tested the effects of MAO-I as an adjunct to levodopa, in comparison to levodopa or dopamine (DA) agonists alone, on various cognitive, affective and quality of life measures.
  
  
  METHODS
  We studied three groups of subjects: healthy controls, PD patients on combined levodopa and MAO-I, and PD patients on levodopa or DA agonists only.
  
  
  RESULTS
  We found that compared to monotherapy, combined MAO-I and levodopa seemed to improve cognition, including probabilistic learning, working memory and executive functions. There were no differences between the different medication regimes on deterministic learning, attention or memory recall. It was also found that MAO-I as an adjunct to levodopa improves affective measures such as depression, apathy, anxiety and quality of life. Interestingly, this enhancing effect of combined levodopa and MAO-I was more pronounced in PD patients with severe akinesia, compared to patients with severe tremor.
  
  
  CONCLUSIONS
  Our data are in agreement with (a) the Continuous Dopaminergic Stimulation (CDS) theory which states that continuous stimulation of the basal ganglia enhances motor, psychiatric and cognitive functions in PD patients; and/or (b) findings that MAO-I increase the bioavailability of monoamines that have beneficial effects on motor and behavioral dysfunction in PD.
authors.affiliation: Department of Psychiatry, Robert Wood Johnson Medical School, Rutgers University NJ, USA.
authors.forename: Rakhee
authors.initials: R
authors.lastname: Krishna
authors.affiliation: School of Medicine, Ain Shams University Cairo, Egypt.
authors.forename: Manal
authors.initials: M
authors.lastname: Ali
authors.affiliation: School of Social Sciences and Psychology and Marcs Institute for Brain and Behaviour, University of Western Sydney Sydney, NSW, Australia.
authors.forename: Ahmed A
authors.initials: AA
authors.lastname: Moustafa
keywords: MAO inhibitors; Parkinson’s disease; anxiety; cognition; depression; learning; quality of life; working memory