Topotecan !

A camptothecin that traps topoisomerase I. Used in relapsed ovarian and small cell lung cancer and in cervical cancer; severe myelosuppression is its main risk.

Updated 2026-11-01

Class: Topoisomerase inhibitors
Enzyme: DNA topoisomerase I
ATC code: L01CE01

DNA topoisomerase ITopotecan

The crystal shows topotecan stacked between DNA base pairs at the cut site of human topoisomerase I.

Target in 3D: DNA topoisomerase I. PDB structure 1K4T (RCSB PDB, public domain). View the structure at RCSB PDB

Mechanism of action

Topotecan binds the topoisomerase I–DNA complex and prevents religation of the single-strand break. Replication enzymes running into the trapped complex create double-strand DNA damage, which mammalian cells cannot repair efficiently.

Topotecan binds the topoisomerase I–DNA complex
The single-strand nick is not resealed
Replication turns it into a double-strand break

Pharmacokinetics

Absorption: Intravenous infusion.
Distribution: About a third is bound to plasma proteins.
Metabolism: Its active lactone ring opens reversibly, depending on pH, to an inactive hydroxy-acid form.
Elimination: Mainly in the urine; the dose is reduced in kidney impairment.
Half-life: About 2 to 3 hours.

Indications

Metastatic ovarian cancer after progression on earlier chemotherapy. Ovarian cancer →
Small cell lung cancer, platinum-sensitive disease that relapses. Lung cancer →
Stage IV-B, recurrent or persistent cervical cancer, with cisplatin. Cervical cancer →

Adverse effects

Common

Neutropenia, thrombocytopenia and anaemia
Nausea, vomiting and diarrhoea
Fatigue and breathlessness

Contraindications

History of severe hypersensitivity to topotecan
The first cycle is not given unless neutrophils and platelets are adequate

Key interactions

Cisplatin: Used together in cervical cancer; marrow suppression adds up, including severe anaemia.
Other myelosuppressive drugs or radiotherapy: Additive bone-marrow toxicity.

What is monitored

Blood counts frequently during each cycle
Kidney function (dose adjustment)
Fever with abdominal pain (typhlitis) and respiratory symptoms

Administration and safety

Given as an intravenous infusion; the site is watched, and extravasation is stopped and managed at once.
Kidney function is checked before preparation, because the dose depends on it.
Hazardous drug: prepared and given following hazardous-drug handling procedures (impervious gloves, no skin contact) and disposed of as cytotoxic waste.

Nursing care

Independent double check of drug, patient, route and cycle before giving it (high-alert medicine).
Confirm adequate neutrophils and platelets before each cycle.
Report fever with abdominal pain at once (neutropenic enterocolitis).
Teaching: report fever, chills, sore throat, bleeding or bruising at once.

Pregnancy and breastfeeding

Can cause fetal harm (embryolethal and teratogenic in animals); effective contraception is used during treatment.

Test yourself

Think of the answer, then tap the question to see it.

Which enzyme does topotecan inhibit?

Topoisomerase I.

What is the boxed warning for topotecan?

Severe myelosuppression; the first cycle is given only with adequate baseline neutrophils and platelets.

Why is the topotecan dose reduced in kidney impairment?

It is eliminated mainly in the urine, so exposure and marrow toxicity rise.

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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: DailyMed - TOPOTECAN HYDROCHLORIDE injection, powder, lyophilized, for solution (DailyMed (U.S. National Library of Medicine), 2026); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 70 (McGraw Hill, 2023); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

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Representative model, for educational purposes only.