Drug interactions
Dexamethasone-tobramycin + Fosphenytoin
Severity: Moderate
Dexamethasone-tobramycin and Fosphenytoin: 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 is a strong CYP3A4 inducer and can substantially lower systemic dexamethasone exposure, while dexamethasone may alter phenytoin levels. The legacy mechanism concerning tobramycin is not meaningful.
What this interaction means in plain words
Dexamethasone-tobramycin and Fosphenytoin 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.
Dexamethasone-tobramycin belongs to Anti Bacterial; Fosphenytoin belongs to Central Nervous System.
Why it happens
CYP3A4 induction by phenytoin increases dexamethasone clearance; dexamethasone may variably alter phenytoin concentrations.
What to do
With systemic dexamethasone, monitor corticosteroid response and consider a higher dose. Check phenytoin levels when corticosteroid therapy starts or stops.
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 Dexamethasone-tobramycin
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 Dexamethasone-tobramycin with Fosphenytoin?
MediHelp rates the interaction as moderate. Dexamethasone-tobramycin and Fosphenytoin 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 is a strong CYP3A4 inducer and can substantially lower systemic dexamethasone exposure, while dexamethasone may alter phenytoin levels. The legacy mechanism concerning tobramycin is not meaningful.
How serious is the interaction between Dexamethasone-tobramycin and Fosphenytoin?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: With systemic dexamethasone, monitor corticosteroid response and consider a higher dose. Check phenytoin levels when corticosteroid therapy starts or stops.
What other medicines interact with Dexamethasone-tobramycin?
MediHelp also lists interactions of Dexamethasone-tobramycin with, for example, Capreomycin, Carboplatin, Ciprofloxacin. The full list is on the Dexamethasone-tobramycin page.
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