Chemotherapy: bleomycin lung toxicity: 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 · Chemotherapy: bleomycin lung toxicity

Sample item

A 24-year-old man receiving bleomycin, etoposide and cisplatin for a testicular tumour has a dry cough, dyspnoea and fine basal crackles. DLCO is reduced and the white cell count is normal. Which statement about this toxicity is correct?

AThe drug is mainly myelosuppressive and spares the lungBLung and skin have low bleomycin hydrolase, and high inspired oxygen raises the riskCIt occurs only with low cumulative dosesDToxicity is prevented by prior folinic acid rescue

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

The answer and the reasoning

B. Lung and skin have low bleomycin hydrolase, and high inspired oxygen raises the risk

Bleomycin is inactivated by bleomycin hydrolase, which is low in lung and skin, so these organs are damaged by free radicals formed with iron. Pulmonary fibrosis is dose related and common above about 400 units, and high fractional oxygen during anaesthesia increases the risk. Marrow suppression is minimal, which makes it useful in combinations.

Option by option

A. The drug is mainly myelosuppressive and spares the lung
Bleomycin is notable for sparing the marrow and for lung and skin toxicity.
B. Lung and skin have low bleomycin hydrolase, and high inspired oxygen raises the risk (correct)
Correct. Low inactivation in these tissues, with oxygen toxicity, explains the pulmonary fibrosis.
C. It occurs only with low cumulative doses
Risk rises with cumulative dose, so toxicity is not restricted to low doses.
D. Toxicity is prevented by prior folinic acid rescue
Folinic acid has no role in bleomycin toxicity; it rescues antifolates.

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 B, Lung and skin have low bleomycin hydrolase, and high inspired oxygen raises the risk. Bleomycin is inactivated by bleomycin hydrolase, which is low in lung and skin, so these organs are damaged by free radicals formed with iron.

Why is "The drug is mainly myelosuppressive and spares the lung" not the answer?

Bleomycin is notable for sparing the marrow and for lung and skin toxicity.

Why is "It occurs only with low cumulative doses" not the answer?

Risk rises with cumulative dose, so toxicity is not restricted to low doses.

Why is "Toxicity is prevented by prior folinic acid rescue" not the answer?

Folinic acid has no role in bleomycin toxicity; it rescues antifolates.

What concept does this question test?

It tests Chemotherapy: bleomycin lung toxicity in Pharmacology. Pulmonary fibrosis is dose related and common above about 400 units, and high fractional oxygen during anaesthesia increases the risk. Marrow suppression is minimal, which makes it useful in combinations.

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 Chemotherapy: bleomycin lung toxicity?

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.