Antiepileptics: fosphenytoin: practice question

A Pharmacology 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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Pharmacology · Antiepileptics: fosphenytoin

Sample item

Why is fosphenytoin preferred over intravenous phenytoin for status epilepticus loading?

AIt has no cardiac effects at allBIt is more potent at the sodium channelCIt avoids all drug interactionsDIt is water soluble, can be infused faster, and avoids propylene glycol and tissue injury such as purple glove syndrome

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

The answer and the reasoning

D. It is water soluble, can be infused faster, and avoids propylene glycol and tissue injury such as purple glove syndrome

Fosphenytoin is a water-soluble phosphate ester prodrug converted to phenytoin, free of the propylene glycol vehicle of phenytoin injection. Local tissue toxicity is reduced, although cardiac monitoring is still needed.

Option by option

A. It has no cardiac effects at all
Cardiac monitoring is still needed.
B. It is more potent at the sodium channel
The active drug is phenytoin, so potency is the same.
C. It avoids all drug interactions
Interactions persist since phenytoin is the active moiety.
D. It is water soluble, can be infused faster, and avoids propylene glycol and tissue injury such as purple glove syndrome (correct)
Correct. Solubility and safer infusion define its advantage.

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.

Questions about this Pharmacology question

What is the answer to this Pharmacology question?

The best answer is D, It is water soluble, can be infused faster, and avoids propylene glycol and tissue injury such as purple glove syndrome. Fosphenytoin is a water-soluble phosphate ester prodrug converted to phenytoin, free of the propylene glycol vehicle of phenytoin injection.

Why is "It has no cardiac effects at all" not the answer?

Cardiac monitoring is still needed.

Why is "It is more potent at the sodium channel" not the answer?

The active drug is phenytoin, so potency is the same.

Why is "It avoids all drug interactions" not the answer?

Interactions persist since phenytoin is the active moiety.

What concept does this question test?

It tests Antiepileptics: fosphenytoin in Pharmacology. Local tissue toxicity is reduced, although cardiac monitoring is still needed.

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 Antiepileptics: fosphenytoin?

Learn drugs as classes, then the exception in each class that an examiner would pick. Then use the flashcards and the other Pharmacology 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.