Drug interactions
Phenytoin + Sofosbuvir-velpatasvir
Severity: Major
Phenytoin and Sofosbuvir-velpatasvir: 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
Phenytoin is a potent inducer of P-gp and CYP enzymes and may substantially lower sofosbuvir and velpatasvir levels. This risks treatment failure, and labeling advises against use together.
What this interaction means in plain words
Phenytoin and Sofosbuvir-velpatasvir 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.
Phenytoin belongs to Central Nervous System; Sofosbuvir-velpatasvir belongs to Anti Virals.
Why it happens
Phenytoin induces P-gp, CYP2B6, CYP2C8 and CYP3A4, increasing clearance and reducing absorption of both antivirals.
What to do
Avoid the combination and use a non-inducing antiepileptic such as levetiracetam. If it cannot be changed, involve a specialist and verify sustained virologic response.
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-velpatasvir
- Rifampin + Sofosbuvir-velpatasvir Contraindicated
- Rifapentine + Sofosbuvir-velpatasvir Contraindicated
- Sofosbuvir-velpatasvir + St john's wort Contraindicated
- Amiodarone + Sofosbuvir-velpatasvir Major
- Apalutamide + Sofosbuvir-velpatasvir Major
- Carbamazepine + Sofosbuvir-velpatasvir Major
Other interactions of Phenytoin
- Artemether / lumefantrine + Phenytoin Contraindicated
- Bictegravir + Phenytoin Contraindicated
- Cabotegravir + Phenytoin Contraindicated
- Doravirine + Phenytoin Contraindicated
- Elbasvir / grazoprevir + Phenytoin Contraindicated
- Elvitegravir / cobicistat / emtricitabine / tenofovir df + Phenytoin Contraindicated
Frequently asked questions
Can I take Phenytoin with Sofosbuvir-velpatasvir?
MediHelp rates the interaction as major. Phenytoin and Sofosbuvir-velpatasvir 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. Phenytoin is a potent inducer of P-gp and CYP enzymes and may substantially lower sofosbuvir and velpatasvir levels. This risks treatment failure, and labeling advises against use together.
How serious is the interaction between Phenytoin and Sofosbuvir-velpatasvir?
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 and use a non-inducing antiepileptic such as levetiracetam. If it cannot be changed, involve a specialist and verify sustained virologic response.
What other medicines interact with Sofosbuvir-velpatasvir?
MediHelp also lists interactions of Sofosbuvir-velpatasvir with, for example, Rifampin, Rifapentine, St john's wort. The full list is on the Sofosbuvir-velpatasvir page.
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