Etoposide: an update

The chemistry, pharmacology, pharmacokinetics, clinical efficacy, adverse effects, and pharmacodynamics of etoposide are reviewed. Etoposide, although similar in chemical structure to podophyllotoxin, has a different mechanism of cytotoxicity compared with its parent compound. Etoposide may stabilize type II topoisomerase-DNA complexes, preventing rejoining of single- and double-strand DNA breaks. Etoposide may also require cellular activation into intermediates, which then bind to DNA and disrupt cellular function. Oral etoposide has an average bioavailability of 50% (range, 17%-137%), with substantial intrapatient and interpatient variability. Etoposide is widely distributed in the body and is highly bound to plasma proteins (greater than 95%). Approximately 50% (range, 20%-81%) of an etoposide dose is recovered in the urine as parent drug or glucuronide, with the remainder of the dose being unaccounted for. The disposition of etoposide in patients with renal and hepatic dysfunction is discussed. Etoposide is effective in combination with other agents against lung cancer, and response rates of 90% in small-cell lung cancer have been observed. When etoposide is used in combination with other agents, response rates of approximately 80% have been observed in patients with testicular cancer. The activity of etoposide in treating leukemia, lymphoma, and breast and ovarian carcinomas and other tumors is discussed. The impact of etoposide on prolonging survival in lung and testicular cancer is addressed, and studies evaluating the pharmacodynamics of etoposide are described. Adverse effects associated with etoposide therapy include myelosuppression, alopecia, nausea and vomiting, mucositis, and hypotension after rapid intravenous administration. Etoposide has demonstrated considerable clinical efficacy against a broad spectrum of tumors.