Drug interactions
Fosphenytoin + Linagliptin-metformin
Severity: Moderate
Fosphenytoin and Linagliptin-metformin: 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, which is converted to phenytoin, induces CYP3A4 and P-glycoprotein and can lower linagliptin exposure, reducing its glucose-lowering effect. Phenytoin may also impair insulin release and raise blood glucose, which can work against metformin. Glycemic control may deteriorate, and it may worsen further as fosphenytoin exposure changes.
What this interaction means in plain words
Fosphenytoin and Linagliptin-metformin 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; Linagliptin-metformin belongs to Endocrine.
Why it happens
Induction of CYP3A4 and P-glycoprotein by phenytoin lowers linagliptin levels, and phenytoin-related hyperglycemia opposes metformin pharmacodynamically.
What to do
Monitor blood glucose and HbA1c after starting or stopping fosphenytoin, and consider an alternative antidiabetic agent if linagliptin response is lost. Watch for hypoglycemia when fosphenytoin is withdrawn.
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 Linagliptin-metformin
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 Linagliptin-metformin?
MediHelp rates the interaction as moderate. Fosphenytoin and Linagliptin-metformin 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, which is converted to phenytoin, induces CYP3A4 and P-glycoprotein and can lower linagliptin exposure, reducing its glucose-lowering effect. Phenytoin may also impair insulin release and raise blood glucose, which can work against metformin. Glycemic control may deteriorate, and it may worsen further as fosphenytoin exposure changes.
How serious is the interaction between Fosphenytoin and Linagliptin-metformin?
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 after starting or stopping fosphenytoin, and consider an alternative antidiabetic agent if linagliptin response is lost. Watch for hypoglycemia when fosphenytoin is withdrawn.
What other medicines interact with Linagliptin-metformin?
MediHelp also lists interactions of Linagliptin-metformin with, for example, Apalutamide, Carbamazepine, Contrast media. The full list is on the Linagliptin-metformin page.
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