Which of the following drugs is not a tocolytic drug?

PGIMER Sangrur NO - 2023

Pharmacology

Easy

Appeared in: PGIMER Sangrur NO - 2023

Explanation

Misoprostol is a prostaglandin E1 analogue, which makes it a uterine stimulant (oxytocic or uterotonic).
Its primary function is to cause uterine contractions, making it useful for inducing labor, ripening the cervix, and managing postpartum hemorrhage.
This action is the direct opposite of tocolytic drugs, which aim to relax the uterus and stop contractions.

Option A: Magnesium sulphate is a well-known tocolytic agent. It acts as a calcium antagonist, interfering with calcium's role in muscle contraction, thereby relaxing the uterine muscle.
Option B: Ritodrine is a beta-2 adrenergic agonist. Its primary mechanism is to stimulate beta-2 receptors on the uterine muscle, leading to smooth muscle relaxation and cessation of contractions.
Option C: Indomethacin is a non-steroidal anti-inflammatory drug (NSAID). It functions as a tocolytic by inhibiting the synthesis of prostaglandins, which are crucial for initiating and maintaining uterine contractions.

Clinical Relevance

Nursing practice connection: Knowing Classification of uterine-acting drugs: Tocolytics vs. Oxytocics helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Nurses must clearly distinguish between tocolytics and oxytocics to ensure patient safety. Administering the wrong class of drug can have catastrophic consequences, such as causing uterine rupture or exacerbating hemorrhage.
In a preterm labor scenario, a tocolytic is required to stop contractions. In a postpartum hemorrhage scenario, an oxytocic is required to make the uterus contract and control bleeding.
What if? If a patient with postpartum hemorrhage was mistakenly given a tocolytic like Magnesium Sulphate instead of an oxytocic like Misoprostol, the uterine atony would worsen, leading to massive, uncontrolled bleeding and potentially maternal death.

How to Approach the Question

First, identify the core of the question. It asks for the drug that is not a tocolytic. This is a negative-elimination question.
Define the key term: 'Tocolytic'. Tocolytics are drugs used to suppress or relax uterine contractions, primarily to stop preterm labor.
Review each option's primary use in obstetrics.
Option A, Magnesium sulphate, is a classic tocolytic. Option B, Ritodrine, is a beta-agonist tocolytic. Option C, Indomethacin, is an NSAID used as a tocolytic.
Option D, Misoprostol, is a prostaglandin used to induce labor and cause contractions. Its action is opposite to that of a tocolytic.
Therefore, Misoprostol is the drug that does not fit the 'tocolytic' category and is the correct answer.

Concept Tested & Keywords

Concept Tested: Classification of uterine-acting drugs: Tocolytics vs. Oxytocics
Stem keywords: tocolytic drug
Lead-in keywords: not
Negative lead-in flag: Question asks to identify the option that does NOT belong to the specified class (Tocolytic).

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