Topotecan is a semi-synthetic derivative of camptothecin and a topoisomerase inhibitor. The chemical name for topotecan hydrochloride is (S)-10-[(dimethylamino)methyl]-4-ethyl-4,9-dihydroxy-1H-pyranoindolizino[1,2-b]quinoline-3,14-(4H,12H)-dione 1.25 hydrochloride. It has the molecular formula C23H23N3O5∙xHCl (x=1.25) and a molecular weight of 467.02. It is soluble in water and melts with decomposition at 213°C to 218°C.
Topotecan hydrochloride has the following structural formula:
Topotecan Injection for intravenous use is supplied as a sterile, non-pyrogenic, clear, yellow to yellow-green solution in single-dose vial at a topotecan free base concentration of 4 mg/4 mL (1 mg/mL).
Each mL contains 1 mg topotecan free base (equivalent to 1.11 mg of topotecan hydrochloride), 5 mg tartaric acid, NF and water for injection, USP. It may also contain hydrochloric acid and/or sodium hydroxide to adjust the pH. The solution pH ranges from 2.6 to 3.2.