Drug interactions
Metformin-sitagliptin + Phenytoin
Severity: Moderate
Metformin-sitagliptin and Phenytoin: 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 can inhibit insulin release and cause hyperglycemia, which may reduce the effectiveness of metformin and sitagliptin. Glucose control may improve again once phenytoin is withdrawn.
What this interaction means in plain words
Metformin-sitagliptin and Phenytoin 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.
Metformin-sitagliptin belongs to Endocrine; Phenytoin belongs to Central Nervous System.
Why it happens
Phenytoin suppresses pancreatic insulin secretion, opposing glucose-lowering therapy.
What to do
Monitor blood glucose when phenytoin is started, changed or stopped, and adjust antidiabetic therapy 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-sitagliptin
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 Metformin-sitagliptin with Phenytoin?
MediHelp rates the interaction as moderate. Metformin-sitagliptin and Phenytoin 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 can inhibit insulin release and cause hyperglycemia, which may reduce the effectiveness of metformin and sitagliptin. Glucose control may improve again once phenytoin is withdrawn.
How serious is the interaction between Metformin-sitagliptin and Phenytoin?
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 phenytoin is started, changed or stopped, and adjust antidiabetic therapy accordingly.
What other medicines interact with Metformin-sitagliptin?
MediHelp also lists interactions of Metformin-sitagliptin with, for example, Clozapine, Contrast media, Diatrizoate meglumine / diatrizoate. The full list is on the Metformin-sitagliptin page.
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