Drug interactions
Fosphenytoin + Nateglinide
Severity: Moderate
Fosphenytoin and Nateglinide: moderate 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, the active form of fosphenytoin, induces CYP2C9 and CYP3A4 and may lower nateglinide levels, reducing its glucose-lowering effect. Phenytoin also has narrow therapeutic index, but nateglinide is unlikely to affect its levels meaningfully.
What this interaction means in plain words
Fosphenytoin and Nateglinide can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Fosphenytoin belongs to Central Nervous System; Nateglinide belongs to Endocrine.
Why it happens
Enzyme induction of CYP2C9 and CYP3A4 by phenytoin increases nateglinide clearance.
What to do
Monitor blood glucose when fosphenytoin is started or stopped, and increase the nateglinide dose if control is lost. Monitor phenytoin levels as clinically indicated.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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Other interactions of Nateglinide
- Albiglutide + Nateglinide Moderate
- Alogliptin-metformin + Nateglinide Moderate
- Alogliptin-pioglitazone + Nateglinide Moderate
- Alogliptin + Nateglinide Moderate
- Alpelisib + Nateglinide Moderate
- Amiodarone + Nateglinide Moderate
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 Nateglinide?
MediHelp rates the interaction as moderate. Fosphenytoin and Nateglinide can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Phenytoin, the active form of fosphenytoin, induces CYP2C9 and CYP3A4 and may lower nateglinide levels, reducing its glucose-lowering effect. Phenytoin also has narrow therapeutic index, but nateglinide is unlikely to affect its levels meaningfully.
How serious is the interaction between Fosphenytoin and Nateglinide?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor blood glucose when fosphenytoin is started or stopped, and increase the nateglinide dose if control is lost. Monitor phenytoin levels as clinically indicated.
What other medicines interact with Nateglinide?
MediHelp also lists interactions of Nateglinide with, for example, Albiglutide, Alogliptin-metformin, Alogliptin-pioglitazone. The full list is on the Nateglinide page.
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