Drug interactions
Fosphenytoin + Sofosbuvir
Severity: Major
Fosphenytoin and Sofosbuvir: 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
Fosphenytoin is converted to phenytoin, an inducer of P-gp and other enzymes that can lower sofosbuvir exposure. Reduced levels of the active metabolite risk hepatitis C treatment failure.
What this interaction means in plain words
Fosphenytoin and Sofosbuvir 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; Sofosbuvir belongs to Anti Virals.
Why it happens
Phenytoin induces intestinal P-gp, reducing sofosbuvir absorption.
What to do
Avoid coadministration; switch to a non-inducing anticonvulsant such as levetiracetam where possible.
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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Other interactions of Sofosbuvir
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 Sofosbuvir?
MediHelp rates the interaction as major. Fosphenytoin and Sofosbuvir 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, an inducer of P-gp and other enzymes that can lower sofosbuvir exposure. Reduced levels of the active metabolite risk hepatitis C treatment failure.
How serious is the interaction between Fosphenytoin and Sofosbuvir?
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 coadministration; switch to a non-inducing anticonvulsant such as levetiracetam where possible.
What other medicines interact with Sofosbuvir?
MediHelp also lists interactions of Sofosbuvir with, for example, Amiodarone, Apalutamide, Carbamazepine. The full list is on the Sofosbuvir page.
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