Etopul Mechanism of Action

Pharmacology: Pharmacodynamics: Etoposide is a semi-synthetic podophyllotoxin derivative. Its main effect seems to occur during the G₂ phase of the cell cycle. Two dose-dependent reactions occur: At high concentrations (>10 μg/mL), lysis can be observed of the cells entering mitosis; at low concentrations (0.3-10 μg/mL), the cells are prevented from entering the prophase. The main macromolecular effect appears to be inhibition of DNA synthesis.
Pharmacokinetics: Following administration by mouth absorption is variable, but on average about 50% of the dose of etoposide is absorbed. The pharmacokinetics of etoposide are subject to considerable interindividual variation. It is rapidly distributed, and concentrations in plasma fall in a biphasic manner, with a terminal half-life of 3 to 19 hours. It is extensively bound to plasma protein (about 94%). Etoposide is excreted in urine and feces as unchanged drug and metabolites: about 45% of a dose is reported to be excreted in urine over 72 hours, two-thirds as unchanged drug. It crosses the blood-brain barrier poorly, with concentrations in CSF from 1 to 10% of those in plasma.