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Drug interactions

Valproic acid + Vorinostat

Severity: Major

Valproic acid and Vorinostat: major interaction.

Last updated

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

Vorinostat causes thrombocytopenia, and valproate can lower platelet counts and impair platelet function. Taken together they raise the risk of severe thrombocytopenia and gastrointestinal bleeding. Both drugs are histone deacetylase inhibitors, so valproate may also add to vorinostat's effects.

What this interaction means in plain words

Valproic acid and Vorinostat 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.

Valproic acid belongs to Central Nervous System; Vorinostat belongs to Oncology.

Evidence level: Moderate

Why it happens

Additive myelosuppressive and platelet-lowering effects, with overlapping histone deacetylase inhibition.

What to do

Avoid the combination where possible. If used together, monitor platelet counts frequently, about every 2 weeks for the first 2 months, and reduce the dose or stop treatment if thrombocytopenia or bleeding occurs.

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?

Bring a full list of your medicines, including over-the-counter products, supplements and herbal remedies, to every pharmacy visit.

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Frequently asked questions

Can I take Valproic acid with Vorinostat?

MediHelp rates the interaction as major. Valproic acid and Vorinostat 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. Vorinostat causes thrombocytopenia, and valproate can lower platelet counts and impair platelet function. Taken together they raise the risk of severe thrombocytopenia and gastrointestinal bleeding. Both drugs are histone deacetylase inhibitors, so valproate may also add to vorinostat's effects.

How serious is the interaction between Valproic acid and Vorinostat?

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 used together, monitor platelet counts frequently, about every 2 weeks for the first 2 months, and reduce the dose or stop treatment if thrombocytopenia or bleeding occurs.

What other medicines interact with Valproic acid?

MediHelp also lists interactions of Valproic acid with, for example, Ertapenem, Imipenem / cilastatin / relebactam, Imipenem / cilastatin. The full list is on the Valproic acid page.

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