Drug interactions
Clozapine + Lomustine
Severity: Major
Clozapine and Lomustine: major interaction.
Last updated Sources: UK SmPC
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Both agents can suppress bone marrow, and clozapine carries a risk of severe neutropenia and agranulocytosis. Combining it with lomustine, which causes delayed and prolonged myelosuppression, increases the risk of serious blood count depression and infection.
What this interaction means in plain words
Clozapine and Lomustine can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Clozapine belongs to Central Nervous System; Lomustine belongs to Oncology.
Why it happens
Additive myelosuppression.
What to do
Avoid the combination where possible; if unavoidable, monitor the absolute neutrophil count and full blood count frequently, including several weeks after each lomustine dose. Interrupt clozapine according to neutropenia protocols.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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References
- Clozapine Viatris 100 mg Orodispersible Tablets - SmPC sections 4.3/4.5 (class statement: cytotoxic agents; "Bone marrow suppressants (e.g. carbamazapine, chloramphenicol), sulphonamides (e.g. co-trimoxazole), pyrazolone analgesics (e.g. phenylbutazone), penicillamine,") — electronic medicines compendium (UK SmPC)
Other interactions of Clozapine
- Clozapine + Deferiprone Contraindicated
- Clozapine + Irinotecan Contraindicated
- Clozapine + Pimozide Contraindicated
- Clozapine + Thioridazine Contraindicated
- Acalabrutinib + Clozapine Major
- Adagrasib + Clozapine Major
Other interactions of Lomustine
- Adenovirus types 4 and 7 live + Lomustine Contraindicated
- Bcg vaccine live + Lomustine Contraindicated
- Influenza virus vaccine quadrivalent intranasal + Lomustine Contraindicated
- Lomustine + Measles mumps and rubella vaccine Contraindicated
- Lomustine + Measles mumps and rubella vaccine live Contraindicated
- Lomustine + Measles mumps rubella and varicella vaccine live Contraindicated
Frequently asked questions
Can I take Clozapine with Lomustine?
MediHelp rates the interaction as major. Clozapine and Lomustine can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Both agents can suppress bone marrow, and clozapine carries a risk of severe neutropenia and agranulocytosis. Combining it with lomustine, which causes delayed and prolonged myelosuppression, increases the risk of serious blood count depression and infection.
How serious is the interaction between Clozapine and Lomustine?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid the combination where possible; if unavoidable, monitor the absolute neutrophil count and full blood count frequently, including several weeks after each lomustine dose. Interrupt clozapine according to neutropenia protocols.
What other medicines interact with Clozapine?
MediHelp also lists interactions of Clozapine with, for example, Deferiprone, Irinotecan, Pimozide. The full list is on the Clozapine page.
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