Drug interactions
Fosphenytoin + Glibenclamide
Severity: Moderate
Fosphenytoin and Glibenclamide: 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 is converted to phenytoin, which induces CYP2C9 and CYP3A4 and may speed glyburide metabolism and weaken glycemic control. Phenytoin can also impair insulin secretion and raise blood glucose, adding to the problem.
What this interaction means in plain words
Fosphenytoin and Glibenclamide 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; Glibenclamide belongs to Endocrine.
Why it happens
Phenytoin induces hepatic CYP2C9 and CYP3A4, increasing glyburide clearance, and has a direct hyperglycemic effect.
What to do
Monitor blood glucose when starting or stopping fosphenytoin and adjust the glyburide dose as required.
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 Glibenclamide
- Bosentan + Glibenclamide Contraindicated
- Cholic acid + Glibenclamide Major
- Ciprofloxacin + Glibenclamide Major
- Clarithromycin + Glibenclamide Major
- Fluconazole + Glibenclamide Major
- Glibenclamide + Insulin degludec-liraglutide Major
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 Glibenclamide?
MediHelp rates the interaction as moderate. Fosphenytoin and Glibenclamide 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 is converted to phenytoin, which induces CYP2C9 and CYP3A4 and may speed glyburide metabolism and weaken glycemic control. Phenytoin can also impair insulin secretion and raise blood glucose, adding to the problem.
How serious is the interaction between Fosphenytoin and Glibenclamide?
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 the glyburide dose as required.
What other medicines interact with Glibenclamide?
MediHelp also lists interactions of Glibenclamide with, for example, Bosentan, Cholic acid, Ciprofloxacin. The full list is on the Glibenclamide page.
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