Toxicology and antidotes: multiple-dose activated charcoal: 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 · Toxicology and antidotes: multiple-dose activated charcoal

Sample item

In which of these overdoses does repeated-dose activated charcoal enhance elimination of the drug?

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

The answer and the reasoning

A. Theophylline

Repeated doses of charcoal interrupt enterohepatic and enteroenteric circulation and can bind drug diffusing back into the gut lumen, which helps for drugs such as theophylline, carbamazepine, phenobarbitone, dapsone and quinine. Iron, lithium and alcohols are poorly adsorbed.

Option by option

  • A. Theophylline (correct)

    Correct. Theophylline is adsorbed by charcoal, and repeated dosing hastens clearance.

  • B. Methanol

    Methanol and other small alcohols are not adsorbed by charcoal.

  • C. Iron

    Iron is not adsorbed by charcoal and needs whole bowel irrigation or chelation.

  • D. Lithium

    Lithium is not bound by charcoal and is removed by saline and dialysis.

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 Pharmacology question

What is the answer to this Pharmacology question?

The best answer is A, Theophylline. Repeated doses of charcoal interrupt enterohepatic and enteroenteric circulation and can bind drug diffusing back into the gut lumen, which helps for drugs such as theophylline, carbamazepine, phenobarbitone, dapsone and quinine.

Why is "Methanol" not the answer?

Methanol and other small alcohols are not adsorbed by charcoal.

Why is "Iron" not the answer?

Iron is not adsorbed by charcoal and needs whole bowel irrigation or chelation.

Why is "Lithium" not the answer?

Lithium is not bound by charcoal and is removed by saline and dialysis.

What concept does this question test?

It tests Toxicology and antidotes: multiple-dose activated charcoal in Pharmacology. Iron, lithium and alcohols are poorly adsorbed.

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 Toxicology and antidotes: multiple-dose activated charcoal?

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.