Drug interactions
Calcifediol + Phenytoin
Severity: Moderate
Calcifediol 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 induces hepatic enzymes that accelerate the breakdown of vitamin D metabolites. This shortens the half-life of calcifediol and can lower active vitamin D status. Long-term use may contribute to reduced bone mineral density and osteomalacia.
What this interaction means in plain words
Calcifediol 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.
Calcifediol belongs to Musculoskeletal; Phenytoin belongs to Central Nervous System.
Why it happens
Enzyme induction by phenytoin increases the hydroxylation and clearance of calcifediol.
What to do
Monitor serum 25-hydroxyvitamin D, calcium and parathyroid hormone periodically. Increase the calcifediol dose if levels or calcium remain low.
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 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
Other interactions of Calcifediol
- Amlodipine-hydrochlorothiazide-valsartan + Calcifediol Moderate
- Amlodipine-olmesartan-hydrochlorothiazide + Calcifediol Moderate
- Amobarbital + Calcifediol Moderate
- Atenolol-chlorthalidone + Calcifediol Moderate
- Azilsartan-chlorthalidone + Calcifediol Moderate
- Calcifediol + Candesartan-hydrochlorothiazide Moderate
Frequently asked questions
Can I take Calcifediol with Phenytoin?
MediHelp rates the interaction as moderate. Calcifediol 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 induces hepatic enzymes that accelerate the breakdown of vitamin D metabolites. This shortens the half-life of calcifediol and can lower active vitamin D status. Long-term use may contribute to reduced bone mineral density and osteomalacia.
How serious is the interaction between Calcifediol 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 serum 25-hydroxyvitamin D, calcium and parathyroid hormone periodically. Increase the calcifediol dose if levels or calcium remain low.
What other medicines interact with Phenytoin?
MediHelp also lists interactions of Phenytoin with, for example, Artemether / lumefantrine, Bictegravir, Cabotegravir. The full list is on the Phenytoin page.
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