A subclass of antineoplastic drugs known as natural products in-cludes:
· vinca alkaloids
Podophyllotoxins are semisynthetic glycosides that are cell cycle–specific and act during the G2 and late S phases of the cell cycle. They include:
Etoposide is effective in the treatment of testicular cancer, non-Hodgkin’s lymphoma, lung cancer, and acute leukemia. Teniposide has demonstrated some activity in treating Hodgkin’s disease, lym-phomas, and brain tumors.
When taken orally, podophyllotoxins are only moderately ab-sorbed. Although the drugs are widely distributed throughout the body, they achieve poor CSF levels.
Podophyllotoxins undergo liver metabolism and are excreted pri-marily in urine.
Although their mechanism of action isn’t completely understood, podophyllotoxins produce several biochemical changes in tumor cells.
At low concentrations, these drugs block cells at the late S or G2 phase. At higher concentrations, they arrest the cells in the G2 phase.
Podophyllotoxins can also break one of the strands of the DNA molecule and can inhibit nucleotide transport and incorporation into nucleic acids.
Etoposide is used to treat testicular cancer lymphomas, prostate cancer, and small-cell lung cancer. Teniposide is used to treat acute lymphoblastic leukemia.
Podophyllotoxins have few significant interactions with other drugs.
· Etoposide may increase the risk of bleeding in a patient taking warfarin.
· Teniposide may increase the clearance and intracellular levels of methotrexate. (See Adverse reactions to podophyllotoxins.)