A semisynthetic derivative of camptothecin, topotecan inhibits the activity of topoisomerase I, an enzyme necessary for DNA replication.

Metastatic carcinoma of the ovary after failure of initial or subsequent therapy; small cell lung cancer after failure of first-line chemotherapy.

Metabolized in the liver. About 30% of the drug is excreted by the kidneys. Renal clearance is an important determinant of topotecan elimination. Half-life: 3 hours.

♦ Adult: 1.5 mg/m² IV for 5 consecutive days every 21 days. At least four courses are recommended, because clinical studies show that the median time for a response is 9 to 12 weeks. In the event of severe neutropenia, reduce the dose by 0.25 mg/m² for the subsequent courses. Alternatively, granulocyte colony-stimulating factor (G-CSF)
may be administered before the subsequent course starting on day 6 (24 hours after the completion of the fifth-day topotecan dose) before resorting to dose reduction. If the patient has a creatinine clearance of 20 to 39 mL/min, reduce the dose to 0.75 mg/mL. No dose requirement is indicated for patients with hepatic impairment.