Drug interactions
Fosphenytoin + Metformin-repaglinide
Severity: Moderate
Fosphenytoin and Metformin-repaglinide: 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
Fosphenytoin induces CYP3A4 and CYP2C8 and can lower repaglinide exposure, weakening its glucose-lowering effect. Phenytoin can also impair insulin secretion and raise blood glucose, which may counteract both components of the combination. Glycemic control may deteriorate, and hypoglycemia may occur if fosphenytoin is later stopped.
What this interaction means in plain words
Fosphenytoin and Metformin-repaglinide 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-repaglinide belongs to Endocrine.
Why it happens
Enzyme induction (CYP3A4/CYP2C8) lowers repaglinide levels, and phenytoin-related inhibition of insulin release is a pharmacodynamic antagonism of antidiabetic action.
What to do
Monitor blood glucose and HbA1c when starting fosphenytoin and titrate the antidiabetic dose as needed. Watch for hypoglycemia and reassess doses when fosphenytoin is discontinued.
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-repaglinide
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-repaglinide?
MediHelp rates the interaction as moderate. Fosphenytoin and Metformin-repaglinide 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 induces CYP3A4 and CYP2C8 and can lower repaglinide exposure, weakening its glucose-lowering effect. Phenytoin can also impair insulin secretion and raise blood glucose, which may counteract both components of the combination. Glycemic control may deteriorate, and hypoglycemia may occur if fosphenytoin is later stopped.
How serious is the interaction between Fosphenytoin and Metformin-repaglinide?
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 and HbA1c when starting fosphenytoin and titrate the antidiabetic dose as needed. Watch for hypoglycemia and reassess doses when fosphenytoin is discontinued.
What other medicines interact with Metformin-repaglinide?
MediHelp also lists interactions of Metformin-repaglinide with, for example, Gemfibrozil, Apalutamide, Clarithromycin. The full list is on the Metformin-repaglinide page.
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