NSTK · 01.2026Independent supplement reference

Edition 1.0Updated August 1, 2026

Supplement × Prescription·Evidence index

Calcium and Phenytoin: what the published research says

PubMed indexes 2 records that name Calcium and Phenytoin together, either in the title or in an interaction, co-administration, or pharmacokinetic context. Each one is listed below with its study design and, where the abstract states one, the authors’ own conclusion, quoted and linked. This page reports that literature. It does not tell you whether to combine them.

Studies listed

Human studies

Reviews & meta-analyses

Published

1977–2001

Read the studies ↓ How we select sources

Read this first

An evidence index, not guidance.

Every statement below is attributed to a named, dated, linked source.

This page lists published research relevant to Calcium and Phenytoin. It deliberately does not state whether the combination is safe, whether it interacts, in which direction, at what dose, or how far apart to take them.

A study appearing here is not proof that an interaction exists. Two substances can be named together in a paper that never tested them in combination, and a source listed as background may cover only one of them.
Findings are quoted from each abstract as the authors wrote them. NutriStack has not re-analysed, pooled, or reconciled them, and they may disagree with each other.
NutriStack’s own interaction assessment for this pair is not published here. It has not completed qualified-human clinical review, so it is withheld from search. See the publication gate.
Nothing here is medical advice. Decisions about prescription medication and supplements belong with your prescriber or pharmacist, who can see your full regimen.

The research

2 studies naming Calcium and Phenytoin.

Strongest relevance first: papers naming both substances in the title, then human trials and systematic reviews.

Phenytoin, phospholipids, and calcium.

Neurology · 1977 · PMID 561338

Human subjects

“This enhancement of Ca++-binding may explain the effectiveness of phenytoins in the treatment of hypocalcemic symptoms. Ca++ and phospholipid binding may be important factors in the stabilizing action of phenytoin.”
Goldberg · From the abstract

Names both Calcium and Phenytoin in its title.

Phenytoin and fluorouracil interaction.

The Annals of pharmacotherapy · 2001 · PMID 11724084

Case ReportsHuman subjects

“The nature and extent of this phenytoin-fluorouracil interaction should be elucidated by in vitro investigations and a prospective study. Until then, clinicians should be aware of this potentially serious drug interaction and monitor patients closely for phenytoin toxicity.”
Gilbar et al. · Authors' conclusion

Names Calcium and Phenytoin together in an interaction, co-administration, or pharmacokinetic context.

Limitations

What this evidence cannot tell you.

Search-based evidence indexes have real limits, and it is worth being explicit about them:

Selection. These records were found by searching PubMed titles and abstracts for both substance names alongside interaction and pharmacokinetic terms. Relevant work that phrases things differently, or is not indexed in PubMed, will be missing.
No effect size. The quoted conclusions are the authors’ words about their own study. We have not extracted effect direction or magnitude, and a single study’s conclusion is not a consensus.
Population mismatch. Findings in healthy volunteers, animals, or a specific patient group may not transfer to you, your dose, or your formulation.
Absence is not safety. Few published studies means the combination is under-studied, which is not the same as established as safe.

NutriStack

Track what you actually take.

NutriStack is a free iPhone app for organising a supplement routine: what you take, when, and what the published record says about it. Its exploratory interaction checker covers Calcium, Phenytoin, and several hundred other substances.

The checker is a research and organisation tool, not a clinical decision aid, and its per-pair assessments are excluded from search until they pass claim-level review.

Get NutriStack free → Read the methodology

NutriStack is an informational and organizational tool, not a medical service, and not a substitute for professional advice. Always consult a qualified healthcare professional before starting, stopping, or changing any supplement or medication.