Final answer:
Doxorubicin is the medication that can cross the blood-brain barrier and treat CNS tumors effectively.
Step-by-step explanation:
Doxorubicin is the medication that is able to cross the blood-brain barrier and effectively treat central nervous system (CNS) tumors. Unlike other medications listed, such as lomustine, vincristine, and omacetaxine, doxorubicin has the ability to pass through the barrier and reach the tumor site in the brain.
The blood-brain barrier is a protective mechanism that prevents many substances, including medications, from entering the brain. However, doxorubicin, which is an anthracycline chemotherapy drug, is able to infiltrate the barrier.
For example, doxorubicin works by intercalating with DNA and inhibiting the enzyme topoisomerase II, which affects the synthesis of DNA and RNA. By inhibiting these processes, doxorubicin can effectively treat CNS tumors.