Research Articles

Antipsychotic Medications: Linking Receptor Antagonism to Neuropsychological Functioning in First Episode Psychosis

Heather A. Baitz^a1, Allen E. Thornton^a1 c1, Ric M. Procyshyn^a2, Geoffrey N. Smith^a2, G. William MacEwan^a2, Lili C. Kopala^a2, Alasdair M. Barr^a3, Donna J. Lang^a4 and William G. Honer^a2

^a1 Department of Psychology, Simon Fraser University, Burnaby, British Columbia

^a2 Department of Psychiatry, University of British Columbia, Vancouver, British Columbia

^a3 Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia

^a4 Department of Radiology, University of British Columbia, Vancouver, British Columbia

Abstract

Antipsychotic medications can contribute to neurocognitive and motor impairments, but specific links to individualized pharmacological treatment regimens are unclear. In 68 participants with stabilized first-episode psychosis (FEP), we investigated the links between neuropsychological functions and an established anticholinergic potency index and a new D₂ antagonist potency index developed in our lab. Each participant's psychiatric medication regimen was converted into estimated receptor antagonist loads based upon specific medication dosage(s) and reported in vitro brain muscarinic cholinergic and D₂ receptor antagonism. In addition to the global neuropsychological impairments of FEP participants, the findings supported the hypothesized links between receptor antagonist loads and specific deficits. Higher anticholinergic load was associated with poorer delayed verbal memory but was not related to motor functioning. In contrast, higher D₂ load was associated with poorer motor functioning but not verbal memory. These selective antagonist load associations explained 19% of the variance in motor functioning and 17% of the variance in delayed verbal memory. Evidently, some of the neuropsychological impairments found in persons with FEP are selectively related to the specific pharmacodynamics and the dosing of their medication regimens. Moreover, these effects can be readily estimated from practical and inexpensive indices. (JINS, 2012, 18, 1–11)

(Received September 27 2011)

(Revised February 22 2012)

(Accepted February 22 2012)

Keywords

• Psychotic disorders;
• Dopamine antagonists;
• Cholinergic antagonists;
• Psychomotor performance;
• Memory;
• Adverse effects

Correspondence:

^c1 Correspondence and reprint requests to: Allen E Thornton, Department of Psychology, Simon Fraser University, Burnaby, BC V5A 1S6, Canada. E-mail: aethornt@sfu.ca