Drug interactions
Fosphenytoin + Metformin-pioglitazone
Severity: Moderate
Fosphenytoin and Metformin-pioglitazone: 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, can inhibit insulin release and raise blood glucose, opposing antidiabetic therapy. Phenytoin may also lower pioglitazone exposure through enzyme induction. Control may worsen on starting and improve on stopping.
What this interaction means in plain words
Fosphenytoin and Metformin-pioglitazone 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; Metformin-pioglitazone belongs to Endocrine.
Why it happens
Phenytoin suppresses insulin secretion and may induce CYP2C8/CYP3A4 metabolism of pioglitazone.
What to do
Monitor blood glucose when starting or stopping fosphenytoin and adjust antidiabetic doses accordingly.
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 Metformin-pioglitazone
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 Metformin-pioglitazone?
MediHelp rates the interaction as moderate. Fosphenytoin and Metformin-pioglitazone 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, can inhibit insulin release and raise blood glucose, opposing antidiabetic therapy. Phenytoin may also lower pioglitazone exposure through enzyme induction. Control may worsen on starting and improve on stopping.
How serious is the interaction between Fosphenytoin and Metformin-pioglitazone?
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 starting or stopping fosphenytoin and adjust antidiabetic doses accordingly.
What other medicines interact with Metformin-pioglitazone?
MediHelp also lists interactions of Metformin-pioglitazone with, for example, Contrast media, Diatrizoate meglumine / diatrizoate, Diatrizoate. The full list is on the Metformin-pioglitazone page.
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