Gemcitabine

Mechanism of action

Inside the cell nucleoside kinases phosphorylate gemcitabine to its diphosphate and triphosphate. The diphosphate inhibits ribonucleotide reductase, so the pool of deoxynucleotides (especially dCTP) falls. The triphosphate then competes more easily with dCTP and is built into DNA, where it ends the strand in a way that resists repair. Cells are blocked at the G1/S boundary.

1. Kinases convert gemcitabine to its diphosphate and triphosphate
2. The diphosphate blocks ribonucleotide reductase: dCTP falls
3. The triphosphate enters DNA and ends the strand
4. Cells stall at the G1/S boundary

Indications

• Pancreatic cancer (first-line, advanced). Pancreatic cancer →
• Non-small cell lung cancer, with cisplatin. Lung cancer →
• Advanced ovarian cancer, with carboplatin. Ovarian cancer →
• Metastatic breast cancer, with paclitaxel. Breast cancer →
• Bladder cancer, in combination regimens. Bladder cancer →

Adverse effects

Common

• Myelosuppression (neutropenia, thrombocytopenia, anaemia)
• Flu-like symptoms: fever, chills, muscle aches, headache
• Oedema, rash
• Nausea, vomiting, raised liver enzymes

Contraindications

• Known hypersensitivity to gemcitabine (including anaphylaxis)

Key interactions

Radiotherapy

Gemcitabine is a radiosensitiser: severe tissue injury when given together or close in time.

Other myelosuppressive chemotherapy (cisplatin, carboplatin, paclitaxel)

Deeper cytopenias, especially thrombocytopenia.

What is monitored

• Complete blood count before each dose
• Kidney function, urine and signs of haemolysis (haemolytic uraemic syndrome)
• Liver tests
• Breathing: new cough or breathlessness

Administration and safety

• The infusion time and weekly schedule are kept as specified: longer infusions or more frequent doses are more toxic.
• Hazardous drug: chemotherapy handling precautions.
• Blood counts are checked before each dose; doses are held or reduced for severe myelosuppression.

Pregnancy and breastfeeding

Can cause fetal harm; effective contraception is advised for women and men.

Nursing care

• Check counts and creatinine before each dose.
• Teach that fever and aches after the infusion are common but that fever with chills during neutropenia is an emergency.
• Report new breathlessness, swelling, dark urine or reduced urine output.
• Check skin in any area that has received radiotherapy.

Pharmacokinetics

Absorption

Intravenous infusion over a fixed, short time (longer infusions increase toxicity).

Metabolism

Rapidly deaminated by cytidine deaminase to an inactive uridine metabolite.

Elimination

Mainly in the urine as the inactive metabolite.

Half-life

Short for the parent drug; longer with long infusions.

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Connections

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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 - GEMCITABINE injection, solution (DailyMed (U.S. National Library of Medicine), 2026); Gemcitabine Injection: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

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