SBA — Single Best Answer · Review
Question 440
Pharmacology → General
Classification
Question
SSBAQuestion Header
A woman receiving an antipsychotic develops galactorrhoea together with rigidity and tremor. Which single pharmacological action provides the best unifying explanation for these adverse effects?
Question Stem
Select the single best answer.
Options
A
Dopamine receptor blockade
B
Presynaptic alpha-2 receptor stimulation
C
Selective serotonin reuptake inhibition
D
Beta-2 receptor stimulation
E
Monoamine oxidase inhibition
Explanation
Antipsychotic drugs act by blocking dopamine receptors. Important consequences include hyperprolactinaemia and extrapyramidal adverse effects, including Parkinsonism, dystonias, akathisia, malignant neuroleptic syndrome and tardive dyskinesia. Galactorrhoea with parkinsonian features therefore points to dopamine receptor blockade.
Option Validity
B) Presynaptic alpha-2 receptor stimulation is the central mechanism described for clonidine.
C) Selective serotonin reuptake inhibition is characteristic of SSRIs and does not explain the paired hyperprolactinaemic and extrapyramidal effects.
D) Beta-2 stimulation is associated with sympathomimetic effects such as bronchodilatation and smooth-muscle relaxation.
E) Monoamine oxidase inhibition is an antidepressant mechanism and is not the mechanism producing this characteristic antipsychotic adverse-effect combination.
Further Reading
Saxena R. Textbook for MRCOG-1. Chapter 12: Pharmacology. Antipsychotic Drugs, pp.345–346.