Drug interactions
Fosphenytoin + Ticlopidine
Severity: Major
Fosphenytoin and Ticlopidine: 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
Ticlopidine inhibits CYP2C19 and can raise phenytoin concentrations, with reports of toxicity such as ataxia and drowsiness. Phenytoin is also an enzyme inducer that could modestly lower ticlopidine exposure.
What this interaction means in plain words
Fosphenytoin and Ticlopidine 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; Ticlopidine belongs to Cardiovascular.
Why it happens
Ticlopidine inhibits CYP2C19 and CYP2C9, reducing phenytoin clearance; phenytoin induction may increase ticlopidine metabolism.
What to do
Monitor phenytoin concentrations when starting or stopping ticlopidine and reduce the fosphenytoin dose as needed. Watch for nystagmus, ataxia and sedation.
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 Ticlopidine
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 Ticlopidine?
MediHelp rates the interaction as major. Fosphenytoin and Ticlopidine 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. Ticlopidine inhibits CYP2C19 and can raise phenytoin concentrations, with reports of toxicity such as ataxia and drowsiness. Phenytoin is also an enzyme inducer that could modestly lower ticlopidine exposure.
How serious is the interaction between Fosphenytoin and Ticlopidine?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor phenytoin concentrations when starting or stopping ticlopidine and reduce the fosphenytoin dose as needed. Watch for nystagmus, ataxia and sedation.
What other medicines interact with Ticlopidine?
MediHelp also lists interactions of Ticlopidine with, for example, Mavacamten, Abrocitinib, Acetylsalicylic acid. The full list is on the Ticlopidine page.
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