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Pharmacology · Antitumour antibiotics

Doxorubicin !

A red anthracycline that wedges into DNA and traps topoisomerase II. Used in breast cancer, lymphomas and sarcomas; it can damage the heart for life.

Updated 2026-11-01

  • Class: Antitumour antibiotics
  • Enzyme: Topoisomerase IIα (and DNA, by intercalation)
  • ATC code: L01DB01
  • WHO Model List of Essential Medicines

Also called: hydroxydaunorubicin

The crystal shows doxorubicin intercalated in a short DNA duplex (no structure of doxorubicin on human topoisomerase II is available).

Target in 3D: Topoisomerase IIα (and DNA, by intercalation). PDB structure 1D12 (RCSB PDB, public domain). View the structure at RCSB PDB

Mechanism of action

Doxorubicin's flat ring slides between DNA base pairs. More important, it forms a complex with DNA and topoisomerase II after the enzyme has cut both strands, so the cut is never resealed and the cell undergoes apoptosis. Its quinone ring cycles with oxygen and iron to produce superoxide and other free radicals, which add DNA damage and are the main explanation for the cumulative heart toxicity, because heart muscle has weak antioxidant defences.

  1. Doxorubicin intercalates between DNA base pairs
  2. Topoisomerase II is trapped after cutting both strands
  3. Double-strand breaks plus free radicals
  4. Tumour cells die; heart muscle is also hurt

Pharmacokinetics

Absorption
Intravenous only.
Distribution
Very wide distribution into tissues; does not cross the blood–brain barrier.
Metabolism
Substrate of CYP3A4, CYP2D6 and P-glycoprotein; reduced to doxorubicinol.
Elimination
Mainly in the bile; little in the urine, which turns red for a day or two. Clearance falls when bilirubin is high.
Half-life
Terminal half-life of about 20 to 48 hours.

Indications

Adverse effects

Common

  • Hair loss (often total)
  • Nausea, vomiting, mouth sores (mucositis)
  • Neutropenia, with a nadir in the second week
  • Red urine for a day or two
  • Red streaking along the vein («flare»), a benign local reaction

Contraindications

  • Severe myocardial insufficiency or a recent myocardial infarction
  • Severe persistent drug-induced myelosuppression
  • Severe hepatic impairment
  • Severe hypersensitivity to doxorubicin

Key interactions

Trastuzumab
Higher risk of heart dysfunction, including after trastuzumab has been stopped; the combination is avoided.
CYP3A4, CYP2D6 or P-glycoprotein inhibitors and inducers
Inhibitors raise doxorubicin levels and toxicity; inducers lower them. Both are avoided.
Paclitaxel
Paclitaxel given first raises doxorubicin levels; doxorubicin is given before paclitaxel.
Dexrazoxane
Starting dexrazoxane together with the first doxorubicin cycles lowered tumour response; it is used once a cumulative dose has been reached.
Mercaptopurine
Doxorubicin may worsen mercaptopurine liver toxicity.

What is monitored

  • Ejection fraction (echocardiogram or MUGA) before, during and after treatment, by the same method each time.
  • Blood count before each dose
  • Bilirubin and liver tests (dose depends on them)
  • Uric acid, potassium, calcium, phosphate and creatinine after the first dose in fast-growing tumours
  • Running total of cumulative anthracycline dose

Administration and safety

  • Vesicant: given only into a free-flowing intravenous line, never intramuscularly or subcutaneously; the site is checked before and during the dose.
  • Continuous infusions run only through a central line.
  • Suspected extravasation (burning, stinging, swelling): stop the drug, try to aspirate without flushing, apply ice intermittently, elevate the limb and notify; dexrazoxane may be used in adults.
  • 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).
  • Check the cumulative anthracycline dose and the latest ejection fraction before each dose.
  • Stay with the patient at the start of the injection and ask about burning or stinging at the site.
  • Teaching: report shortness of breath, swelling of the legs, palpitations or fast weight gain, even months after treatment.
  • Teaching: red urine for a day or two is expected; hair loss is common; report fever or mouth sores.

Pregnancy and breastfeeding

Can cause fetal harm; effective contraception is used during and after treatment, and breastfeeding is not advised.

Test yourself

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

What is the most important long-term toxicity of doxorubicin, and what determines its risk?

Cardiomyopathy with heart failure; the risk rises with the cumulative dose and with other cardiotoxic therapy (e.g. trastuzumab, chest radiation).

Which drug reduces doxorubicin cardiotoxicity, and how?

Dexrazoxane, an iron chelator that limits iron-dependent free-radical damage in the heart.

A patient notices red urine the day after doxorubicin. What is the explanation?

The drug's red colour; it is expected for a day or two and is not blood.

What are the first steps if doxorubicin extravasation is suspected?

Stop the injection, aspirate without flushing, apply ice intermittently, elevate the limb; dexrazoxane may be given in adults.

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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 - DOXORUBICIN HYDROCHLORIDE injection, solution (DailyMed (U.S. National Library of Medicine), 2025); 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); eEML - Electronic Essential Medicines List (World Health Organization, 2025).

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Representative model, for educational purposes only.