A 26-year-old woman treated with risperidone develops amenorrhoea, galactorrhoea, and a serum prolactin of 95 ng/mL. The mechanism responsible is:
- A Blockade of dopamine D2 receptors in the tuberoinfundibular pathway ✓
- B Stimulation of serotonin 5-HT2A receptors in the hypothalamus
- C Direct stimulation of lactotroph D2 receptors
- D Blockade of histamine H1 receptors in the pituitary stalk
Correct answer: A. Blockade of dopamine D2 receptors in the tuberoinfundibular pathway
Explanation
Tuberoinfundibular dopaminergic neurons tonically inhibit prolactin release from the anterior pituitary. D2 blockade by risperidone, among the highest-risk agents along with amisulpride and paliperidone, removes this inhibition and raises prolactin. Clozapine and quetiapine transiently raise prolactin minimally because of their loose D2 binding, which distinguishes them from risperidone in clinical practice.
Reference: Katzung Basic and Clinical Pharmacology, 15th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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