Drug interactions
Fosphenytoin + Rivaroxaban
Severity: Major
Fosphenytoin and Rivaroxaban: major interaction.
Last updated Sources: US FDA label
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
Fosphenytoin is converted to phenytoin, a CYP3A4 and P-gp inducer that lowers rivaroxaban concentrations. This can lead to loss of anticoagulant protection and thrombosis.
What this interaction means in plain words
Fosphenytoin and Rivaroxaban 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.
Fosphenytoin belongs to Central Nervous System; Rivaroxaban belongs to Cardiovascular.
Why it happens
Induction of CYP3A4 and P-gp by phenytoin, increasing rivaroxaban clearance.
What to do
Avoid concurrent use and choose an alternative anticoagulant such as warfarin, with INR monitoring.
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
Other interactions of Rivaroxaban
- Defibrotide + Rivaroxaban Contraindicated
- Ketoconazole + Rivaroxaban Contraindicated
- Ketorolac + Rivaroxaban Contraindicated
- Abciximab + Rivaroxaban Major
- Acalabrutinib + Rivaroxaban Major
- Acetylsalicylic acid + Rivaroxaban Major
Other interactions of Fosphenytoin
- Dronedarone + Fosphenytoin Contraindicated
- Fosphenytoin + Ledipasvir-sofosbuvir Contraindicated
- Fosphenytoin + Lorlatinib Contraindicated
- Fosphenytoin + Lurasidone Contraindicated
- Fosphenytoin + Ranolazine Contraindicated
- Fosphenytoin + Sofosbuvir-velpatasvir-voxilaprevir Contraindicated
Frequently asked questions
Can I take Fosphenytoin with Rivaroxaban?
MediHelp rates the interaction as major. Fosphenytoin and Rivaroxaban 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. Fosphenytoin is converted to phenytoin, a CYP3A4 and P-gp inducer that lowers rivaroxaban concentrations. This can lead to loss of anticoagulant protection and thrombosis.
How serious is the interaction between Fosphenytoin and Rivaroxaban?
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 concurrent use and choose an alternative anticoagulant such as warfarin, with INR monitoring.
What other medicines interact with Rivaroxaban?
MediHelp also lists interactions of Rivaroxaban with, for example, Defibrotide, Ketoconazole, Ketorolac. The full list is on the Rivaroxaban page.
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