Drug interactions
Calcitriol + Phenytoin
Severity: Moderate
Calcitriol 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 enzymes that increase the catabolism of vitamin D metabolites, which may reduce calcitriol effect and contribute to hypocalcemia and bone disease. Patients on long-term anticonvulsants may need closer follow-up of calcium status.
What this interaction means in plain words
Calcitriol 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.
Calcitriol belongs to Musculoskeletal; Phenytoin belongs to Central Nervous System.
Why it happens
Induction of hepatic enzymes, including CYP24 and CYP3A4 pathways, by phenytoin increases calcitriol catabolism.
What to do
Monitor serum calcium, phosphate and PTH, and increase calcitriol dose if hypocalcemia or reduced response occurs.
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 Calcitriol
- Amlodipine-hydrochlorothiazide-valsartan + Calcitriol Moderate
- Amlodipine-olmesartan-hydrochlorothiazide + Calcitriol Moderate
- Amobarbital + Calcitriol Moderate
- Apalutamide + Calcitriol Moderate
- Atazanavir + Calcitriol Moderate
- Atenolol-chlorthalidone + Calcitriol Moderate
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
Frequently asked questions
Can I take Calcitriol with Phenytoin?
MediHelp rates the interaction as moderate. Calcitriol 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 enzymes that increase the catabolism of vitamin D metabolites, which may reduce calcitriol effect and contribute to hypocalcemia and bone disease. Patients on long-term anticonvulsants may need closer follow-up of calcium status.
How serious is the interaction between Calcitriol 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 calcium, phosphate and PTH, and increase calcitriol dose if hypocalcemia or reduced response occurs.
What other medicines interact with Calcitriol?
MediHelp also lists interactions of Calcitriol with, for example, Amlodipine-hydrochlorothiazide-valsartan, Amlodipine-olmesartan-hydrochlorothiazide, Amobarbital. The full list is on the Calcitriol page.
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