Drug interactions
Fosphenytoin + Temsirolimus
Severity: Major
Fosphenytoin and Temsirolimus: 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 potent CYP3A4 inducer that can reduce temsirolimus and sirolimus exposure. This may compromise antitumor efficacy.
What this interaction means in plain words
Fosphenytoin and Temsirolimus 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; Temsirolimus belongs to Oncology.
Why it happens
Induction of CYP3A4 metabolism of temsirolimus by phenytoin.
What to do
Use a non-inducing anticonvulsant such as levetiracetam if possible. If not, labeling suggests considering a higher temsirolimus dose with 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 Temsirolimus
- Bcg vaccine live + Temsirolimus Contraindicated
- Influenza virus vaccine quadrivalent intranasal + Temsirolimus Contraindicated
- Measles mumps and rubella vaccine live + Temsirolimus Contraindicated
- Measles mumps rubella and varicella vaccine live + Temsirolimus Contraindicated
- Measles vaccine + Temsirolimus Contraindicated
- Rotavirus oral vaccine live + Temsirolimus Contraindicated
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 Temsirolimus?
MediHelp rates the interaction as major. Fosphenytoin and Temsirolimus 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 potent CYP3A4 inducer that can reduce temsirolimus and sirolimus exposure. This may compromise antitumor efficacy.
How serious is the interaction between Fosphenytoin and Temsirolimus?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Use a non-inducing anticonvulsant such as levetiracetam if possible. If not, labeling suggests considering a higher temsirolimus dose with monitoring.
What other medicines interact with Temsirolimus?
MediHelp also lists interactions of Temsirolimus with, for example, Bcg vaccine live, Influenza virus vaccine quadrivalent intranasal, Measles mumps and rubella vaccine live. The full list is on the Temsirolimus page.
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