Hypertensive disorders: magnesium in renal impairment: practice question

A OBG question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

Try it

OBG · Hypertensive disorders: magnesium in renal impairment

Sample item

A woman with eclampsia has received a 4 g intravenous loading dose of magnesium sulphate. Her urine output is 15 mL per hour and serum creatinine is raised. How should maintenance be handled?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

A. Reduce or withhold maintenance doses and monitor reflexes and serum levels

Magnesium is cleared by the kidneys, so oliguria and renal impairment cause accumulation and toxicity, with loss of reflexes and respiratory depression. The loading dose is still given, but maintenance is reduced, reflexes, respiration and levels are monitored, and calcium gluconate is kept ready.

Option by option

  • A. Reduce or withhold maintenance doses and monitor reflexes and serum levels (correct)

    Correct. Renal excretion is reduced, so maintenance must be cut and monitored.

  • B. Stop magnesium and switch to phenytoin

    Magnesium sulphate remains the drug of choice, so switching to phenytoin is inappropriate.

  • C. Double the maintenance dose because levels fall in renal failure

    Doubling the dose in renal failure would cause toxicity.

  • D. Give the full intramuscular maintenance doses unchanged

    Unchanged dosing in oliguria risks magnesium toxicity.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

More OBG questions

Questions about this OBG question

What is the answer to this OBG question?

The best answer is A, Reduce or withhold maintenance doses and monitor reflexes and serum levels. Magnesium is cleared by the kidneys, so oliguria and renal impairment cause accumulation and toxicity, with loss of reflexes and respiratory depression.

Why is "Stop magnesium and switch to phenytoin" not the answer?

Magnesium sulphate remains the drug of choice, so switching to phenytoin is inappropriate.

Why is "Double the maintenance dose because levels fall in renal failure" not the answer?

Doubling the dose in renal failure would cause toxicity.

Why is "Give the full intramuscular maintenance doses unchanged" not the answer?

Unchanged dosing in oliguria risks magnesium toxicity.

What concept does this question test?

It tests Hypertensive disorders: magnesium in renal impairment in OBG. The loading dose is still given, but maintenance is reduced, reflexes, respiration and levels are monitored, and calcium gluconate is kept ready.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Hypertensive disorders: magnesium in renal impairment?

Learn management algorithms as steps: PPH, eclampsia, ectopic pregnancy. Then use the flashcards and the other OBG questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.