Drug & supplement interaction

Caprylic Acid + Phenytoin

Phenytoin brand names: Dilantin Kapseals, Dilantin, Di-Phen, Dilantin Infatabs, Phenytek, and others.

No Known Interaction
Medically reviewed by · Updated July 2026 · Pair last verified Sep 20, 2026
The bottom line No known interaction

We found no known interaction between Caprylic Acid and Phenytoin in our sources. Absence of a documented interaction is not the same as proven safety, and does not guarantee one does not exist. Do not start, stop, or change a medication or supplement based on this page; confirm with your pharmacist or doctor first. Additionally, although there is no interaction, the two are separately associated with some of the same side effects, which would make a new symptom harder to attribute to one or the other.

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Interaction report

Caprylic Acid and Phenytoin

We checked these two against our interaction database. Here is what we found.

No Known Interaction Found

We did not find a documented interaction between Phenytoin and Caprylic Acid in our sources. This does not guarantee that the combination is completely free of risk — there is often limited research on supplements and herbal products, especially around drug interactions.

If you decide to take both, the practical routine is simple: add one new thing at a time and note the date you started it. If the combination is going to disagree with you, it usually shows in the first days to a couple of weeks — and a start date turns “I’ve been feeling off” into something a pharmacist can actually work with. Do not stop a prescribed medicine on your own.

Always talk with your pharmacist or doctor before making changes to your medications or supplements, particularly if you take several medications or have an ongoing health condition.

Caprylic Acid safety at a glance

Caprylic Acid overall Use caution Generally recognized as safe in food, but supplement doses are less well studied.
Pregnancy Use caution Food amounts are likely fine, but supplement doses lack safety data, so avoid unless your doctor approves.
Breastfeeding Use caution Caprylic acid occurs naturally in breast milk, but concentrated supplement safety is unknown, so use caution.

Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Still wondering about combining Phenytoin and Caprylic Acid? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Phenytoin

Interactions in our licensed database are recorded against drug classes, not just single drug names. Phenytoin is filed under 14 classifications — including cytochrome p450 2c8 (cyp2c8) substrates, cytochrome p450 2c9 (cyp2c9) inducers, anticonvulsants. Caprylic Acid has documented interactions with 3 drug classes — the most serious being antihypertensive drugs (moderate), nonsteroidal anti-inflammatory drugs (nsaids) (moderate) and warfarin (coumadin) (moderate) — and none of Phenytoin’s classifications are among them.

Classification data comes from our licensed Natural Medicines dataset. A medication can belong to classes beyond those recorded there, so this describes how the check was run — it is not a safety guarantee.

Keep it in perspective

Caprylic Acid Does Interact With Other Medications

Caprylic Acid has 262 moderate known drug interactions in our database — Phenytoin isn’t one of them. If you take anything else, check it against the full list below.

Moderate 262 No known interaction 2,568 (incl. Phenytoin)
Taking anything else?

Check Another of Your Medications Against Caprylic Acid

Covers the 2,830 medications we’ve checked against Caprylic Acid. Pick one to open its full report.

What to actually watch for

No Interaction Found — But Data Suggests Caprylic Acid and Phenytoin May Share Several of the Same Side Effects

This is not an interaction. Neither one changes how your body handles the other, and nothing here says they react together. What our sources do show is that each has separately been linked to the effects below — so taking both can make those effects more likely to turn up, and harder to pin on one or the other if they do.

  • A change in taste Additional detail

    Caprylic Acid

    “Orally, caprylic acid seems to be well tolerated, short-term.

    Most Common Adverse Effects:

    Orally: Mild abdominal discomfort and change in taste perception.

    Topically: Skin irritation.”

    Caprylic Acid · Natural Medicines adverse-effect record, reported in skin irritation.

    Phenytoin

    Listed in the ADVERSE REACTIONS section of the FDA label for Phenytoin. Read the label on DailyMed ›

  • Dizziness / Headache Additional detail

    Caprylic Acid

    “Orally, caprylic acid has rarely been reported to cause mild dizziness, headache, and fatigue.”

    Caprylic Acid · Natural Medicines adverse-effect record, reported in cluster headache.

    1 source cited
    1. 97662. Voller B, Lines E, McCrossin G, et al. Dose-escalation study of octanoic acid in patients with essential tremor. J Clin Invest. 2016;126(4):1451-7. PubMed

    Phenytoin

    Listed in the ADVERSE REACTIONS section of the FDA label for Phenytoin. Read the label on DailyMed ›

Reported for Caprylic Acid but not commonly for Phenytoin: stomach upset and tiredness.

Effects for Phenytoin come from the ADVERSE REACTIONS section of its FDA label; effects for Caprylic Acid come from the Natural Medicines adverse-effect record, quoted above. Wording is matched across sources by our own clinical vocabulary, so treat this as a prompt to pay attention, not a diagnosis.

From our Q&A

Questions About Caprylic Acid or Phenytoin

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Caprylic Acid or Phenytoin, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Phenytoin

This page covers Caprylic Acid only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Phenytoin page lists 224 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: 1,4-butanediol (major), Activated Charcoal (major), Beer (major), Gamma-hydroxybutyrate (ghb) (major) and Kava (major).

By severity: 9 major · 187 moderate · 28 minor.

From our pharmacist’s overview on the Phenytoin page

“Phenytoin (Dilantin) is a seizure medicine with a narrow therapeutic index, meaning small changes in its blood level can bring seizures back or tip over into toxicity, so I treat its supplement list with real seriousness. The biggest group, 78 ingredients, piles on sedation, and alcohol, kava, and GHB all rate major for exactly that re…”

Reviewed by 2 · Jul 18, 2026

Open the Phenytoin interaction page

One more smart check

Taking Caprylic Acid as Part of a Dietary Supplement Product? Check It for Interactions

We hold 514 real supplement products containing Caprylic Acid, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Caprylic Acid. Even though Caprylic Acid itself has no known interaction with Phenytoin, another ingredient on your label might. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Caprylic Acid and Phenytoin Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Caprylic Acid
Top 25%

#329 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Phenytoin
Top 25%

#475 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Where does our data come from?
  • Source: the Natural Medicines (TRC Healthcare) clinical database — the evidence-graded professional reference for herb & supplement interactions.
  • Citation library: 103,510 references behind our interaction content, 65,311 of them resolved to verified PubMed/DOI sources. See every Caprylic Acid reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 20, 2026. The Caprylic Acid and Phenytoin records this page draws on were last updated July 10, 2026.
  • What “no known interaction” means: no documented interaction in the sources above — not a guarantee of safety. Supplements are studied far less than prescription drugs, so we say exactly what the evidence supports, and nothing more.
Data structure & sourcing designed and verified by .
Supplement

About Caprylic Acid

What is Caprylic Acid?

Caprylic Acid
  • Candida and yeast overgrowth
  • Gut health support
  • Antimicrobial
  • Digestive health
  • Part of ketogenic diets

Caprylic acid is a medium-chain fatty acid found in coconut oil and palm kernel oil that is popularly used for yeast overgrowth and gut health. While laboratory studies show it has antimicrobial activity, strong human evidence for most supplement claims is limited. It is generally considered safe in food amounts, but talk with your pharmacist or doctor before using concentrated supplements.

Fatty acid derived from coconut and palm kernel oil; also found in milk fat · Capsules, softgels, liquid oil, part of MCT oil blends

An interaction check asks whether these two react with each other — it does not ask whether Caprylic Acid is a good idea for someone in your situation. Here is what our Caprylic Acid record says about it on its own.

Caprylic Acid: dosing

There is no official, well-established dose for caprylic acid as a supplement. Products vary widely in strength and form, so the right amount depends on the specific product.The safest approach is to follow the directions on the product label and start with a lower amount to see how your body responds.

From our Caprylic Acid monograph — the full record covers uses, side effects and every documented interaction.

Read the full Caprylic Acid monograph & all interactions
Medication

About Phenytoin

What Is Phenytoin Used For?

Brand names: Dilantin Kapseals, Dilantin, Di-Phen, Dilantin Infatabs, Phenytek, Dilantin injection

Phenytoin is used to treat and prevent seizures. The specific types covered depend on the formulation. Oral extended-release capsules (including Phenytek), chewable tablets (including Dilantin Infatabs and Phenytoin Infatabs), and oral suspension (including Dilantin-125) are used for tonic-clonic (grand mal) and psychomotor (temporal lobe) seizures; most oral forms also cover prevention and treatment of seizures occurring during or after neurosurgery. Chewable tablets and some capsule formulations also cover complex partial seizures.

Parenteral (injectable) phenytoin sodium is used for generalized tonic-clonic status epilepticus (a prolonged, life-threatening seizure emergency) and for prevention and treatment of seizures during neurosurgery. The IV form can also substitute short-term for oral phenytoin when a patient cannot take it by mouth.

Most-Reported Side Effects for Phenytoin

From FAERS, the FDA’s public side-effect reporting system (40,278 reports, all brands). Reports are voluntary and are not proof the drug caused the effect.

Convulsion 3,522 reports
Seizure 3,095 reports
Toxicity to various agents 1,888 reports
Fall 1,604 reports
Dizziness 1,539 reports
See full Phenytoin drug information
Keep checking

Other Drugs & Caprylic Acid

Browse every other medication we’ve checked against Caprylic Acid — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
262Moderate
0Minor
2,567No known interaction
262 Moderate 2,567 No interaction
Moderate

262 interactions

Showing 60 of 262 moderate interactions — see all 262 on the Caprylic Acid page.

No interaction 2,567 drugs checked — show the list

We also checked Caprylic Acid against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,567 medications checked with no known interaction — see the full Caprylic Acid list.

See the full Caprylic Acid interactions page
See every supplement checked against Phenytoin, ranked by severity
Evidence & sources

Caprylic Acid References

The 5 references that drive our Caprylic Acid monograph and interaction data, from the evidence-graded Natural Medicines (TRC Healthcare) database. Citations with a link open the study on PubMed or the publisher’s site.

  1. Massolini G, Aubry AF, McGann A, Wainer IW. Determination of the magnitude and enantioselectivity of ligand binding to rat and rabbit serum albumins using immobilized-protein high performance liquid chromatography stationary phases. Biochem Pharmacol 1993 PubMed
  2. Kristev A, Mitkov D, Lukanov Y, Chapkynov P. The effect of octanoic fatty acid on the cardiovascular system of the guinea pig. Cor Vasa 1989;31(4):321-7.
  3. Hayball PF, Holman JW, Nation RL. Influence of octanoic acid on the reversible protein binding of ketorolac enantiomers to human serum albumin (HSA): comparative liquid chromatographic studies using a HSA chiral stationary phase. J Chromatogr B Biomed App PubMed
  4. Noctor TA, Wainer IW, Hage DS. Allosteric and competitive displacement of drugs from human serum albumin by octanoic acid, as revealed by high-performance liquid affinity chromatography, on a human serum albumin-based stationary phase. J Chromatogr 1992;5 PubMed
  5. Voller B, Lines E, McCrossin G, et al. Dose-escalation study of octanoic acid in patients with essential tremor. J Clin Invest. 2016;126(4):1451-7. PubMed

Medication overviews come from MedlinePlus (NIH); supplement label data from the NIH Dietary Supplement Label Database. Content is written and reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

Pharmacist Counseling Corner

Taking Caprylic Acid and Phenytoin Together: Common Questions

Is it safe to take Caprylic Acid with Phenytoin?
We do not list a known interaction between Caprylic Acid and Phenytoin. That does not guarantee the combination is risk-free, so confirm with your pharmacist or doctor — especially if you take other medications or have a health condition.
Do Caprylic Acid and Phenytoin have any of the same side effects?
Yes — our sources link each of them separately to 3 of the same effects. That is not an interaction: neither changes how your body handles the other. It does mean that if one of those effects turns up, it can be harder to tell which one is behind it. They are listed on this page with the source behind each.
How was the Caprylic Acid and Phenytoin combination checked?
Interactions in our licensed database are recorded against drug classes. Phenytoin is filed under 14 classifications, and Caprylic Acid has documented interactions with 3 drug classes — none of Phenytoin's classifications are among them. A medication can belong to classes beyond those recorded in our dataset, so this describes how the check was run rather than guaranteeing safety.
Does Caprylic Acid interact with any other medications?
Yes. Caprylic Acid has 262 documented drug interactions in our database — Phenytoin is simply not one of them. If you take anything else, it is worth checking each one; they are all listed on this page.
Does Phenytoin interact with any supplements?
Yes. Phenytoin has documented interactions with 224 supplements in our database — Caprylic Acid is not one of them. The Phenytoin interaction page linked on this page lists every one, ranked by severity.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Where next

Keep Exploring

Caprylic Acid monograph Uses, safety profile, and every drug interaction in one place Phenytoin drug information The full plain-English guide to this medication Phenytoin supplement interactions Every supplement checked against Phenytoin, ranked by severity Supplement interaction checker Check any supplement or product against your medications Browse medications A–Z Every drug we’ve checked against herbs & supplements References The 5 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Phenytoin and Caprylic Acid?

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.