<p>Although the exact mechanism of action of bleomycin sulfate is unknown, available evidence indicates that the main mode of action is the inhibition of DNA synthesis with some evidence of lesser inhibition of RNA and protein synthesis.<br />
<br />
Bleomycin is known to cause single, and to a lesser extent, double-stranded breaks in DNA. In&nbsp;in vitro&nbsp;and in vivo experiments, bleomycin has been shown to cause cell cycle arrest in G2 and in mitosis. When administered into the pleural cavity in the treatment of malignant pleural effusion, bleomycin sulfate acts as a sclerosing agent.</p>