Intravenous and inhalational agents: midazolam water solubility: practice question

A Anaesthesia 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.

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Anaesthesia · Intravenous and inhalational agents: midazolam water solubility

Sample item

Midazolam is supplied as an aqueous solution that causes little pain on injection, yet it enters the brain quickly after intravenous use. Which property accounts for both observations?

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

The answer and the reasoning

C. The ring opens at the acidic pH of the vial, making it water-soluble, and closes at blood pH to become lipid-soluble

Midazolam has an imidazole ring that opens at low pH, giving a water-soluble form for the vial. At physiological pH the ring closes and the drug becomes highly lipid-soluble, so it enters the brain rapidly. This avoids the propylene glycol of diazepam and its injection pain.

Option by option

  • A. It is dissolved in propylene glycol, which keeps it water-soluble in blood

    Propylene glycol is the solvent of diazepam, and it is the cause of pain on injection with that drug.

  • B. It is a prodrug converted to a lipid-soluble active compound in the liver within seconds

    Midazolam is active as given and does not need hepatic activation before acting.

  • C. The ring opens at the acidic pH of the vial, making it water-soluble, and closes at blood pH to become lipid-soluble (correct)

    Correct. The pH-dependent ring change gives a water-soluble vial form and a lipid-soluble drug in blood.

  • D. It is carried in a lipid emulsion that crosses the blood-brain barrier readily

    Midazolam is not formulated in a lipid emulsion; propofol is.

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.

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Questions about this Anaesthesia question

What is the answer to this Anaesthesia question?

The best answer is C, The ring opens at the acidic pH of the vial, making it water-soluble, and closes at blood pH to become lipid-soluble. Midazolam has an imidazole ring that opens at low pH, giving a water-soluble form for the vial.

Why is "It is dissolved in propylene glycol, which keeps it water-soluble in…" not the answer?

Propylene glycol is the solvent of diazepam, and it is the cause of pain on injection with that drug.

Why is "It is a prodrug converted to a lipid-soluble active compound in the l…" not the answer?

Midazolam is active as given and does not need hepatic activation before acting.

Why is "It is carried in a lipid emulsion that crosses the blood-brain barrie…" not the answer?

Midazolam is not formulated in a lipid emulsion; propofol is.

What concept does this question test?

It tests Intravenous and inhalational agents: midazolam water solubility in Anaesthesia. At physiological pH the ring closes and the drug becomes highly lipid-soluble, so it enters the brain rapidly. This avoids the propylene glycol of diazepam and its injection pain.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. 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 Intravenous and inhalational agents: midazolam water solubility?

Make a table of each agent, its key advantage and its main side effect. Then use the flashcards and the other Anaesthesia 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.