Drug interactions
Ergocalciferol + Fosphenytoin
Severity: Moderate
Ergocalciferol 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
Chronic phenytoin therapy, which fosphenytoin delivers, accelerates vitamin D catabolism and may lead to low vitamin D levels, osteomalacia or reduced bone density. The effect of vitamin D supplements may be blunted.
What this interaction means in plain words
Ergocalciferol 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.
Ergocalciferol belongs to Musculoskeletal; Fosphenytoin belongs to Central Nervous System.
Why it happens
Phenytoin induces hepatic CYP enzymes, increasing the breakdown of vitamin D and its metabolites.
What to do
Monitor 25-hydroxyvitamin D, calcium and bone health in long-term users, and increase vitamin D supplementation as needed.
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 Ergocalciferol
- Aluminum hydroxide + Ergocalciferol Moderate
- Calcium acetate + Ergocalciferol Moderate
- Calcium carbonate + Ergocalciferol Moderate
- Calcium chloride + Ergocalciferol Moderate
- Calcium citrate + Ergocalciferol Moderate
- Calcium gluconate + Ergocalciferol Moderate
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 Ergocalciferol with Fosphenytoin?
MediHelp rates the interaction as moderate. Ergocalciferol 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. Chronic phenytoin therapy, which fosphenytoin delivers, accelerates vitamin D catabolism and may lead to low vitamin D levels, osteomalacia or reduced bone density. The effect of vitamin D supplements may be blunted.
How serious is the interaction between Ergocalciferol 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: Monitor 25-hydroxyvitamin D, calcium and bone health in long-term users, and increase vitamin D supplementation as needed.
What other medicines interact with Ergocalciferol?
MediHelp also lists interactions of Ergocalciferol with, for example, Aluminum hydroxide, Calcium acetate, Calcium carbonate. The full list is on the Ergocalciferol page.
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