Temozolomide
Alkylating agents
Alkylating agentsHigh alert
An error with this medicine can cause serious harm: double checks and protocols are used.
An oral methylating drug that turns into MTIC by itself and reaches the brain. With radiotherapy it is the standard drug for glioblastoma.
Quick facts
- Group
- Alkylating agents
- Target
- DNA (guanine O6 and N7), methylated by MTIC
- Used for
- Newly diagnosed glioblastoma · Anaplastic astrocytoma
- Key effects
- Nausea · Fatigue · Hair loss
- Monitor
- Liver tests at baseline
- ATC
- L01AX03
No doses: the clinician sets them by the current guideline.
Mechanism of action
Temozolomide needs no enzyme: at the body's normal pH it opens up into MTIC, the same active compound made from dacarbazine. MTIC releases a methyl group that attaches to guanine, mainly at O6 and N7. O6-methylguanine is mispaired during copying; repeated failed repair causes DNA breaks and cell death. The repair enzyme MGMT removes the methyl group, so tumours that have silenced the MGMT gene respond better.
- At body pH temozolomide opens into MTIC
- MTIC methylates guanine (O6 and N7)
- Mispaired O6-methylguanine leads to DNA breaks
- Tumours lacking MGMT repair respond best
Indications
- Newly diagnosed glioblastoma, with radiotherapy and then as maintenance. Glioblastoma →
- Anaplastic astrocytoma (adjuvant or refractory).
Adverse effects
Common
- Nausea, vomiting, constipation
- Fatigue, headache
- Hair loss
- Low lymphocytes, neutrophils and platelets
Contraindications
- Serious hypersensitivity to temozolomide or its ingredients
- Serious hypersensitivity to dacarbazine (same active metabolite)
Key interactions
- Corticosteroids (e.g. dexamethasone for brain oedema)
- Deepen lymphopenia and raise the risk of Pneumocystis pneumonia.
- Other myelosuppressive drugs and radiotherapy
- Add to bone marrow suppression.
What is monitored
- Neutrophil and platelet counts before each cycle and during treatment
- Liver tests at baseline, during the first cycle, before each cycle and after the last dose
- Lymphocyte count and signs of pneumonia
Administration and safety
- Capsules are swallowed whole and never opened or chewed; contents on skin or mucosa are washed off at once.
- Taken on an empty stomach or at bedtime to reduce nausea, with an antiemetic as prescribed.
- Pneumocystis prophylaxis is used during the combined radiotherapy phase.
Pregnancy and breastfeeding
Can cause fetal harm; women use effective contraception and men use condoms with partners who could become pregnant.
Nursing care
- Check counts and liver tests before each cycle.
- Confirm the patient understands the exact cycle schedule: mistakes with oral chemotherapy cause overdoses.
- Watch for cough, fever and breathlessness (Pneumocystis), especially on corticosteroids.
- Teaching: safe handling and storage at home; contraception (men use condoms).
Pharmacokinetics
- Absorption
- Oral, well absorbed; it is taken the same way each time with respect to food.
- Distribution
- Small and lipid-soluble: it crosses the blood–brain barrier.
- Metabolism
- Spontaneous chemical conversion to MTIC; little liver metabolism.
- Elimination
- Mainly in the urine.
Test yourself
Think of the answer, then tap the question to see it.
How is temozolomide activated?
Spontaneously at physiological pH, to MTIC; no liver enzyme is needed.
Which tumour feature predicts a better response to temozolomide?
Silencing (methylation) of the MGMT gene, which removes the repair of O6-methylguanine.
Why is temozolomide contraindicated after a serious reaction to dacarbazine?
Both are converted to the same active metabolite, MTIC.
Which opportunistic infection is a concern with temozolomide and corticosteroids?
Pneumocystis jirovecii pneumonia.
Connections
← Back to the class: Alkylating agents
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 - TEMOZOLOMIDE capsule (DailyMed (U.S. National Library of Medicine), 2026); Temozolomide: 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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Representative model, for educational purposes only.