Drug & supplement interaction

Astaxanthin + 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 Astaxanthin 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.

Know someone taking this? Share
Facebook Post Reddit Email
On this page
Interaction report

Astaxanthin 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 Astaxanthin 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.

Astaxanthin safety at a glance

Astaxanthin overall Use caution Generally well tolerated in studies, but long-term safety data are limited.
Pregnancy Avoid Not enough safety data, so it is best to avoid during pregnancy.
Breastfeeding Avoid Not enough safety data, so it is best to avoid while breastfeeding.

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

Still wondering about combining Phenytoin and Astaxanthin? 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. Astaxanthin has documented interactions with 2 drug classes — the most serious being cytochrome p450 2b6 (cyp2b6) substrates (moderate) and cytochrome p450 3a4 (cyp3a4) substrates (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

Astaxanthin Does Interact With Other Medications

Astaxanthin has 671 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 671 No known interaction 2,159 (incl. Phenytoin)
Taking anything else?

Check Another of Your Medications Against Astaxanthin

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

What to actually watch for

What Astaxanthin Itself Has Been Linked To

This is not an interaction — nothing below involves Phenytoin. It is the side-effect record for Astaxanthin on its own, from the licensed Natural Medicines monograph. If something new turns up after you add Astaxanthin, this list is the first place to look.

  • Stomach pain / Diarrhea Additional detail

    “Orally, astaxanthin 6 mg daily has caused two cases of increased bowel movements and two cases of red fecal color. A higher dose of astaxanthin (AstaCarox, AstaReal AB) 40 mg daily has caused severe stomach/abdominal pain in two patients.”

    Astaxanthin · Natural Medicines adverse-effect record, reported in myasthenia gravis.

    2 sources cited
    1. 91736. Choi HD, Youn YK, Shin WG. Positive effects of astaxanthin on lipid profiles and oxidative stress in overweight subjects. Plant Foods Hum Nutr. 2011;66:363-369. PubMed
    2. 19165. Kupcinskas L, Lafolie P, Lignell A, et al. Efficacy of the natural antioxidant astaxanthin in the treatment of functional dyspepsia in patients with or without Helicobacter pylori infection: A prospective, randomized, double blind, and placebo-controlled

Everything above comes from the Natural Medicines adverse-effect record for Astaxanthin — expand a row for the licensed statement it rests on. We read the ADVERSE REACTIONS section of Phenytoin’s FDA label too, and the two lists don’t meaningfully overlap — which is why no Phenytoin column appears here.

From our Q&A

Questions About Astaxanthin 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 Astaxanthin 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 Astaxanthin 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 Astaxanthin as Part of a Dietary Supplement Product? Check It for Interactions

We hold 2,223 real supplement products containing Astaxanthin, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Astaxanthin. Even though Astaxanthin 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 Astaxanthin 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 Astaxanthin
Top 10%

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

29 days ago today
Medication Phenytoin
Top 25%

#557 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 Astaxanthin reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 20, 2026. The Astaxanthin 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 Astaxanthin

What is Astaxanthin?

Astaxanthin
  • Antioxidant support
  • Skin health and aging
  • Eye health
  • Exercise recovery
  • Heart and inflammation support

Astaxanthin is a reddish carotenoid pigment with strong antioxidant activity in the lab, and it is widely promoted for skin, eye, heart, and exercise benefits. Early human studies are promising for a few uses, but the overall evidence is still limited and not strong enough to make firm claims. It appears generally well tolerated at typical supplement doses, but talk with your pharmacist or doctor before starting it.

Pigment extracted from microalgae (mainly Haematococcus pluvialis), yeast, and some seafood · Capsules, soft gels, tablets, and as an ingredient in some skin creams

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

Astaxanthin: dosing

There is no official standardized dose for astaxanthin, and amounts used in studies have varied. Because of this, the best approach is to follow the directions on the product label.Astaxanthin is fat-soluble, so it is often taken with a meal that contains some fat to help absorption.

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

Read the full Astaxanthin 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 & Astaxanthin

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

0Major
671Moderate
0Minor
2,158No known interaction
671 Moderate 2,158 No interaction
Moderate

671 interactions

Showing 60 of 671 moderate interactions — see all 671 on the Astaxanthin page.

No interaction 2,158 drugs checked — show the list

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

Showing the 60 most looked-up of 2,158 medications checked with no known interaction — see the full Astaxanthin list.

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

Astaxanthin References

The 3 references that drive our Astaxanthin 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. Kupcinskas L, Lafolie P, Lignell A, et al. Efficacy of the natural antioxidant astaxanthin in the treatment of functional dyspepsia in patients with or without Helicobacter pylori infection: A prospective, randomized, double blind, and placebo-controlled
  2. Kistler, A., Liechti, H., Pichard, L., Wolz, E., Oesterhelt, G., Hayes, A., and Maurel, P. Metabolism and CYP-inducer properties of astaxanthin in man and primary human hepatocytes. Arch.Toxicol. 2002;75(11-12):665-675. PubMed
  3. Choi HD, Youn YK, Shin WG. Positive effects of astaxanthin on lipid profiles and oxidative stress in overweight subjects. Plant Foods Hum Nutr. 2011;66:363-369. 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 Astaxanthin and Phenytoin Together: Common Questions

Is it safe to take Astaxanthin with Phenytoin?
We do not list a known interaction between Astaxanthin 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.
How was the Astaxanthin and Phenytoin combination checked?
Interactions in our licensed database are recorded against drug classes. Phenytoin is filed under 14 classifications, and Astaxanthin has documented interactions with 2 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 Astaxanthin interact with any other medications?
Yes. Astaxanthin has 671 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 — Astaxanthin 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

Astaxanthin 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 3 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Phenytoin and Astaxanthin?

Our pharmacists answer your medication & supplement questions — free.

Ask a pharmacist

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.