Decitabine

Mechanism of action

Decitabine enters the cell, is phosphorylated and is built into new DNA in place of deoxycytidine. When DNA methyltransferase tries to methylate the altered base, the enzyme stays covalently bound and is used up. Each round of replication then leaves the DNA less methylated, so tumour-suppressor and differentiation genes that were silenced can be expressed again; the cells mature or die by apoptosis. The DNA-protein adducts can also cause double-strand breaks.

1. Decitabine is phosphorylated and built into new DNA
2. DNA methyltransferase is trapped on it and depleted
3. DNA loses methylation; silenced genes switch back on
4. Abnormal marrow cells mature or die

Indications

• Myelodysplastic syndromes, new or previously treated, de novo or secondary. Myelodysplastic syndromes →
• The oral combination with cedazuridine is also used in chronic myelomonocytic leukaemia and acute myeloid leukaemia. Acute leukaemia (AML and ALL) →

Adverse effects

Common

• Neutropenia, thrombocytopenia and anaemia (the most common effects)
• Fever, tiredness
• Nausea, constipation, diarrhoea
• Cough, petechiae
• High blood glucose

Contraindications

• The label lists none; pregnancy is avoided because it can harm the fetus

Key interactions

CYP substrates, inhibitors and inducers

No CYP interactions are expected: decitabine is not a CYP substrate and does not inhibit or induce these enzymes in laboratory studies.

Other myelosuppressive treatments

Add to the fall in blood counts, the drug's main toxicity.

What is monitored

• Complete blood count with platelets before each cycle and as needed
• Liver panel and serum creatinine at baseline
• Signs of infection and bleeding

Administration and safety

• Intravenous infusion only, given in a clinic or hospital.
• If it will not be given soon after mixing, it is diluted with cold infusion fluid and kept refrigerated for a limited time.
• Hazardous drug: prepared and disposed of under cytotoxic-drug procedures.
• Premedication against nausea is given before each dose.

Pregnancy and breastfeeding

Can cause fetal harm; pregnancy is avoided during treatment and for a period afterwards, and breastfeeding is not advised.

Nursing care

• Check the blood count before each cycle; cycles are often delayed for low counts.
• Teach the patient to report fever, chills, cough, bruising or bleeding at once.
• Watch blood glucose and ask about thirst and frequent urination.
• Effective contraception for women and for men with female partners, during and after treatment.

Pharmacokinetics

Absorption

Given intravenously. An oral form combines it with cedazuridine, a cytidine deaminase inhibitor that protects it from breakdown in the gut and liver.

Metabolism

Deaminated by cytidine deaminase, mainly in the liver but also in granulocytes, gut lining and blood; it is not a CYP substrate.

Half-life

Short in plasma, about half an hour, but its effect on DNA lasts much longer.

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Connections

← Back to the class: Antimetabolites

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 - DECITABINE injection, powder, lyophilized, for solution (DailyMed (U.S. National Library of Medicine), 2026); Decitabine and Cedazuridine: 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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