topotecan - Medications

Topotecan is a semi-synthetic derivative of camptothecin and is an anti-tumor drug with topoisomerase I-inhibitory activity. The chemical name for topotecan free base is ( S )-10-[(dimethylamino)methyl]-4-ethyl-4,9-dihydroxy-1 H -pyrano[3’,4’:6,7]indolizino[1,2- b ]quinoline-3,14-(4 H ,12 H )-dione. It has the molecular formula C 23 H 23 N 3 O 5 and a molecular weight of 421.45. Topotecan has three pKa values: pKa 1 = 10.50 corresponding to the benzyldimethylamino group, pKa 2 = 6.99 corresponding to the phenol group and pKa 3 = 0.60 corresponding to the quinoline group. As formulated in Topotecan Injection, topotecan has the following structural formula: where n is >1, corresponding to HCl added to adjust the pH to approximately 1.5 to 2.5. Topotecan Injection is supplied as a sterile, non-pyrogenic, clear, yellow solution at a topotecan free base concentration of 4 mg/4 mL (1 mg/mL) and 1 mg/mL available in multiple dose vials. Each mL of Topotecan Injection contains topotecan hydrochloride equivalent to 1 mg of topotecan as free base, 5 mg tartaric acid, NF, and water for injection, USP. Hydrochloric acid and/or sodium hydroxide may be used to adjust the pH.. The hydrochloride salt of topotecan is soluble in water and melts with decomposition at 213 ° C to 218°C. The solution must be diluted before administration by intravenous infusion. structural formula