Which drug causes lactation suppression in a postnatal mother?

DSSSB -28 August 2019 (Shift-2)

Pharmacology

Medium

Appeared in: DSSSB -28 August 2019 (Shift-2)

Explanation

Bromocriptine is a dopamine D2 receptor agonist.
The hypothalamus releases dopamine, which acts as a prolactin-inhibiting hormone (PIH).
By mimicking the action of dopamine, bromocriptine directly suppresses the release of prolactin from the anterior pituitary gland.
Prolactin is the principal hormone responsible for stimulating milk production (lactogenesis).
Therefore, by reducing prolactin levels, bromocriptine effectively suppresses or stops lactation.

Option A: Metoclopramide is a dopamine antagonist. It blocks dopamine's inhibitory effect on the pituitary, leading to an increase in prolactin secretion and can therefore induce or enhance lactation (a known side effect is galactorrhea).
Option B: Oxytocin does not affect milk production. Its role is to stimulate the contraction of myoepithelial cells around the mammary alveoli, causing the milk ejection or 'let-down' reflex.
Option D: Sulpiride, like metoclopramide, is a dopamine antagonist. It increases prolactin levels and is known to cause galactorrhea (milk production) as a side effect.

Clinical Relevance

Nursing practice connection: Knowing Pharmacological suppression of lactation helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Lactation suppression is a necessary medical intervention in tragic circumstances such as stillbirth or neonatal death, or when breastfeeding is contraindicated for the mother (e.g., active HIV, certain medications).
Nurses should first encourage and educate patients on non-pharmacological methods for lactation suppression, such as wearing a firm bra, avoiding nipple stimulation, and using cold packs for engorgement.
When administering dopamine agonists like bromocriptine, it is vital for the nurse to monitor for adverse effects, particularly postural hypotension at the start of therapy, and to be aware of the rare but serious cardiovascular risks.

How to Approach the Question

First, identify the core physiological process in the question: 'lactation suppression'.
Recall the key hormones involved in lactation: Prolactin for milk production and Oxytocin for milk ejection ('let-down').
Remember the primary regulatory mechanism for prolactin: Dopamine from the hypothalamus inhibits its release.
Analyze the options based on this regulatory pathway. A drug that suppresses lactation must logically either mimic dopamine (an agonist) or block prolactin directly.
Evaluate each option: Bromocriptine is a known dopamine agonist. Metoclopramide and Sulpiride are dopamine antagonists (they would increase prolactin). Oxytocin is related to ejection, not production.
Conclude that the dopamine agonist, Bromocriptine, is the only option that will suppress prolactin and therefore suppress lactation.

Concept Tested & Keywords

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E6 Pharmacology Katzung 16e pp. 1059-1061, 1064-1066

E6 Pharmacology KD Tripathi Essentials 9e Part 1 p. 288-290