Question

Pulmonary fibrosis is a common complication with

• A. 6 mercaptopurine
• B. Vincristine
• C. Bleomycin
• D. Adriamycin

Hint:

Bleomycin is poorly broken down in lung tissue, so free radical damage builds up there and causes pulmonary fibrosis; this is its dose limiting toxicity.

Answer 1

The Correct Option is C

Step 1: Recall each drug's class and its typical toxicity.
6 mercaptopurine is an antimetabolite whose main worries are bone marrow suppression and liver toxicity. Vincristine is a vinca alkaloid best known for peripheral neuropathy from its effect on microtubules. Adriamycin, also called doxorubicin, is an anthracycline whose signature toxicity is dose related cardiomyopathy and heart failure.

Step 2: Focus on bleomycin.
Bleomycin is an antitumour antibiotic that works by causing free radical mediated DNA strand breaks. Its dose limiting toxicity is not on the bone marrow, unlike most chemotherapy drugs, but on the lungs.

Step 3: Understand why the lung is the target.
Lung tissue has low levels of the enzyme bleomycin hydrolase compared with other organs, so the drug is not broken down efficiently there. This lets reactive oxygen species build up in lung tissue and damage alveolar cells, which over time leads to interstitial pneumonitis and progressive pulmonary fibrosis.

Step 4: Note the clinical relevance.
This toxicity is cumulative dose dependent and is worsened by high inspired oxygen, so anaesthetists are taught to avoid giving high concentration oxygen to patients who have received bleomycin.

Final Answer:
Of the four drugs, only bleomycin has pulmonary fibrosis as its defining toxicity.
\[ \boxed{\text{Bleomycin}} \]