Antipsychotic drugs are prescribed to decrease the psychotic symptoms by?

RRB Nsg. Superintendent 21 July 2019 (shift 1st)

Pharmacology

Easy

Appeared in: RRB Nsg. Superintendent 21 July 2019 (shift 1st)

Explanation

Antipsychotic drugs primarily work by blocking dopamine receptors, specifically the D2 subtype, in various pathways of the brain.
This mechanism is based on the 'dopamine hypothesis,' which posits that an overactivity of dopamine in the mesolimbic pathway is responsible for the positive symptoms of psychosis (e.g., hallucinations, delusions).
By antagonizing these dopamine receptors, antipsychotics reduce this excessive neuronal firing, leading to a reduction in psychotic symptoms.
The clinical potency of most first-generation antipsychotics is directly correlated with their affinity for blocking D2 receptors.

Option A: While sedation is a common side effect of many antipsychotics, CNS depression is not their primary therapeutic mechanism for treating psychosis. This action is more characteristic of sedative-hypnotics or anxiolytics.
Option B: This describes the mechanism of Monoamine Oxidase Inhibitors (MAOIs), a class of antidepressants. They inhibit the enzyme monoamine oxidase, thereby increasing the levels of neurotransmitters like serotonin, norepinephrine, and dopamine.
Option D: This is the primary mechanism of action for several classes of antidepressants, including Tricyclic Antidepressants (TCAs) and Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs).

Visual 1: Diagram: A synaptic cleft showing an antipsychotic drug molecule physically blocking the postsynaptic D2 dopamine receptor, preventing dopamine from binding.
Visual 2: Flowchart: A chart comparing the primary neurotransmitter targets for different classes of psychotropic medications: Antipsychotics (Dopamine), Antidepressants (Serotonin/Norepinephrine), and Anxiolytics (GABA).

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Mechanism of Action of Antipsychotic Drugs as background academic context rather than a clinical decision trigger.
A nurse's primary role is to monitor for both the therapeutic effects (e.g., reduced delusions, clearer thought processes) and the significant adverse effects of dopamine blockade, such as Extrapyramidal Symptoms (EPS) like tremors, rigidity, and dystonia.
Patient education is critical. The nurse must teach the patient and family to recognize early signs of EPS and to understand the importance of not stopping the medication abruptly, which can lead to relapse.
What if? If a patient taking an antipsychotic develops a high fever, severe muscle rigidity, and confusion, the nurse must recognize these as signs of Neuroleptic Malignant Syndrome (NMS). This is a life-threatening emergency requiring immediate cessation of the drug and urgent medical intervention.

How to Approach the Question

First, identify the core subject of the question: the mechanism of 'antipsychotic drugs'.
Second, recall the fundamental theory related to psychosis and its treatment, which is the 'dopamine hypothesis'. This links psychosis to excess dopamine.
Third, evaluate each option based on this core knowledge. The correct option should relate to reducing dopamine's effect.
Fourth, systematically eliminate the other options by identifying which drug classes they describe. Recognize that CNS depression, MAO inhibition, and serotonin/norepinephrine reuptake blockade are mechanisms for other psychotropic drugs (anxiolytics and antidepressants).

Concept Tested & Keywords

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