What is the loading dose of MgSO4 in eclampsia?

Appeared in: AIIMS Delhi NO - 2018

Explanation

The standard loading dose of magnesium sulfate (MgSO₄) for treating eclampsia and severe preeclampsia is 4 to 6 grams (gm).
This dose is typically administered as an intravenous (IV) infusion over 15-20 minutes to rapidly achieve a therapeutic serum level.
The primary goal of the loading dose is to act as a central nervous system depressant to prevent or control eclamptic seizures.

Option B: The unit 'mcg' (microgram) is incorrect. A dose of 4 mcg is a million times smaller than the required 4 gm dose and would have no therapeutic effect.
Option C: Both the value (10) and the unit 'mg' (milligram) are incorrect. A 10 mg dose is a thousand times smaller than the required gram-level dose and is clinically insignificant for seizure prevention in eclampsia.
Option D: Both the value (10) and the unit 'mcg' (microgram) are incorrect. This represents a minuscule dose that is far below the therapeutic threshold for eclampsia.

Clinical Relevance

Nursing practice connection: Knowing Pharmacology: MgSO4 dosage for eclampsia helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Nurses must be extremely vigilant with high-alert medications like MgSO₄. A critical safety check is to confirm the dose and the unit (grams vs. milligrams vs. micrograms), as an error can be fatal.
The primary nursing responsibility during MgSO₄ infusion is to monitor for signs of toxicity: loss of deep tendon reflexes, respiratory rate below 12 breaths/min, and urine output below 30 mL/hr.
What if? If the patient's respiratory rate drops to 10 breaths/min and her patellar reflexes are absent, the nurse's first action is to immediately stop the magnesium sulfate infusion and notify the physician. The next step is to prepare to administer the antidote, calcium gluconate, as ordered.

How to Approach the Question

First, identify the key components of the question: the drug (MgSO₄), the condition (eclampsia), and the specific dose type (loading dose).
This is a factual recall question testing knowledge of a standard obstetric emergency protocol.
Pay close attention to the units in the options (gm, mcg, mg). Medication dosage questions frequently test the ability to distinguish between these units, as errors can be life-threatening.
Recall that eclampsia is a seizure disorder requiring a significant dose of an anticonvulsant. This makes gram-level dosing plausible and microgram or milligram-level dosing highly unlikely for a loading dose.
Based on standard guidelines, the loading dose is 4-6 grams. Select the option that matches this value and unit.

Concept Tested & Keywords

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E6 Obstetrics Williams p. 31-51

Practise the full AIIMS Delhi NO - 2018

Attempt every question from this paper in a timed mock, then review the full solution for each one.