Drug & supplement interaction

Swamp Milkweed + Phenylephrine

Phenylephrine brand names: Gilchew, AH Chew D, Gilchew IR, Sudafed PE, Biorphen.

No Known Interaction
Medically reviewed by · Updated July 2026 · Pair last verified Oct 4, 2026
The bottom line No known interaction

We found no known interaction between Swamp Milkweed and Phenylephrine 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

Swamp Milkweed and Phenylephrine

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 Phenylephrine and Swamp Milkweed 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.

Swamp Milkweed safety at a glance

Swamp Milkweed overall Use caution The plant contains toxic sap and cardiac glycoside-like compounds; it is not a well-studied or clearly safe supplement.
Pregnancy Likely Unsafe When used orally due to presence of cardioactive steroids; avoid using. Read the full pregnancy detail
Breastfeeding Likely Unsafe When used orally due to presence of cardioactive steroids; avoid using. Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center) — the full detail is in the Special populations card below. Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Still wondering about combining Phenylephrine and Swamp Milkweed? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Phenylephrine

Interactions in our licensed database are recorded against drug classes, not just single drug names. Phenylephrine is filed under 5 classifications — including alpha-adrenergic agonists, stimulant drugs, serotonergic drugs. Swamp Milkweed has documented interactions with 7 drug classes — the most serious being digoxin (lanoxin) (major), quinine (major) and corticosteroids (moderate) — and none of Phenylephrine’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

Swamp Milkweed Does Interact With Other Medications

Swamp Milkweed has 3 major, 153 moderate known drug interactions in our database — Phenylephrine isn’t one of them. If you take anything else, check it against the full list below.

Major 3 Moderate 153 No known interaction 2,674 (incl. Phenylephrine)
Taking anything else?

Check Another of Your Medications Against Swamp Milkweed

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

What to actually watch for

No Interaction Found — But Data Suggests Swamp Milkweed and Phenylephrine 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.

  • Headache reported in 7.8% of FDA reports for Phenylephrine Additional detail

    Swamp Milkweed

    “Orally, the cardiac glycosides in swamp milkweed may cause headache and stupor (18). Visual color disturbances may also occur (18).”

    Swamp Milkweed · Natural Medicines adverse-effect record, reported in cluster headache.

    1 source cited
    1. 18. Gruenwald J, Brendler T, Jaenicke C. PDR for Herbal Medicines. 1st ed. Montvale, NJ: Medical Economics Company, Inc., 1998.

    Phenylephrine

    Listed in the ADVERSE REACTIONS section of the FDA label for Phenylephrine, and in voluntary FDA adverse-event reports. Read the label on DailyMed ›

  • Vomiting Additional detail

    Swamp Milkweed

    “Orally, large amounts of swamp milkweed can cause vomiting (18).”

    Swamp Milkweed · Natural Medicines adverse-effect record, reported in nausea and vomiting.

    1 source cited
    1. 18. Gruenwald J, Brendler T, Jaenicke C. PDR for Herbal Medicines. 1st ed. Montvale, NJ: Medical Economics Company, Inc., 1998.

    Phenylephrine

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

Reported for Swamp Milkweed but not commonly for Phenylephrine: an irregular heartbeat.

Effects for Phenylephrine come from the ADVERSE REACTIONS section of its FDA label; effects for Swamp Milkweed come from the Natural Medicines adverse-effect record, quoted above. Where a percentage is shown, it is the share of 221,388 voluntary FDA FAERS reports for Phenylephrine that mention that effect — a reporting proportion, not an incidence rate and not evidence the drug caused it. Wording is matched across sources by our own clinical vocabulary, so treat this as a prompt to pay attention, not a diagnosis.

Special populations

Swamp Milkweed in Pregnancy & Breastfeeding

Pregnancy And Lactation Likely Unsafe

When used orally due to presence of cardioactive steroids; avoid using.

DISCLAIMER: This tool is intended for informational purposes only, and should not be interpreted as specific medical advice. Patients should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.© 2026 Therapeutic Research Center

From our Q&A

Questions About Swamp Milkweed or Phenylephrine

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Swamp Milkweed or Phenylephrine, 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 Phenylephrine

This page covers Swamp Milkweed only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Phenylephrine page lists 81 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Ephedra (major), Lithium (major), Peyote (major) and Rauvolfia Vomitoria (major).

By severity: 6 major · 60 moderate · 15 minor.

From our pharmacist’s overview on the Phenylephrine page

“If you take phenylephrine (Sudafed PE, Biorphen) for congestion, treat this list as one that needs real attention, since six of its 81 entries carry a major rating. Phenylephrine tightens blood vessels to clear your nose, and more than half of the interactions here come from stimulant ingredients, ephedra above all, that can push blood…”

Reviewed by 2 · Jul 18, 2026

Open the Phenylephrine interaction page

How much people look this up

Where Swamp Milkweed and Phenylephrine 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 Swamp Milkweed
Top half

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

29 days ago today
Medication Phenylephrine
Top half

#749 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 Swamp Milkweed reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified October 4, 2026. The Swamp Milkweed and Phenylephrine 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 Swamp Milkweed

What is Swamp Milkweed?

  • Traditional digestive remedy
  • Diuretic (increasing urine)
  • Cough and respiratory complaints
  • Worm or parasite remedy (folk use)
  • Pollinator/garden plant rather than medicine

Swamp Milkweed is a native North American wetland plant best known today as a butterfly and pollinator garden plant, not a proven medicine. It contains toxic milky sap with cardiac glycoside-like compounds, and there is very little reliable human research to support any health use. Because of its potential toxicity, it should not be used as a supplement without professional guidance.

Asclepias incarnata · Apocynaceae · Root, and historically other parts of the plant · Dried root, tinctures, and traditional decoctions (rarely sold as a commercial supplement)

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

Swamp Milkweed: dosing

There is no established safe or standardized dose for Swamp Milkweed. It is not a mainstream supplement, and reliable products with verified content are not generally available.Because of the plant's toxicity and the lack of research, we cannot recommend any specific amount. For most people, the safest approach is to enjoy Swamp Milkweed as a garden plant rather than to consume it.

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

Read the full Swamp Milkweed monograph & all interactions
Medication

About Phenylephrine

What Is Phenylephrine Used For?

Brand names: Gilchew, AH Chew D, Gilchew IR, Sudafed PE, Biorphen

Phenylephrine is used in several different products, and each one has its own use.

Injection (IV): raises blood pressure in adults with clinically important hypotension (low blood pressure) caused mainly by widened blood vessels. Some injections are labeled for anesthesia only. Others are labeled for anesthesia and septic shock.

Eye drops: Phenylephrine Hydrochloride Ophthalmic Solution is used to dilate the pupil.

Nasal products: temporarily relieve nasal and sinus congestion from the common cold, hay fever or other upper respiratory allergies.

Rectal suppositories: relieve itching, burning and discomfort from hemorrhoids and temporarily shrink hemorrhoidal tissue.

Most-Reported Side Effects for Phenylephrine

From FAERS, the FDA’s public side-effect reporting system (221,388 reports, all brands). Reports are voluntary and are not proof the drug caused the effect.

Fatigue 20,609 reports
Headache 17,301 reports
Nausea 16,925 reports
Diarrhea 14,221 reports
Dyspnea 13,719 reports
See full Phenylephrine drug information
Keep checking

Other Drugs & Swamp Milkweed

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

3Major
153Moderate
0Minor
2,673No known interaction
3 Major 153 Moderate 2,673 No interaction
Major

3 interactions

Moderate

153 interactions

Showing 60 of 153 moderate interactions — see all 153 on the Swamp Milkweed page.

No interaction 2,673 drugs checked — show the list

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

Showing the 60 most looked-up of 2,673 medications checked with no known interaction — see the full Swamp Milkweed list.

See the full Swamp Milkweed interactions page
See every supplement checked against Phenylephrine, ranked by severity
Evidence & sources

Swamp Milkweed References

The 3 references that drive our Swamp Milkweed 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. Blumenthal M, ed. The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. Trans. S. Klein. Boston, MA: American Botanical Council, 1998.
  2. Ellenhorn MJ, et al. Ellenhorn's Medical Toxicology: Diagnoses and Treatment of Human Poisoning. 2nd ed. Baltimore, MD: Williams & Wilkins, 1997.
  3. Gruenwald J, Brendler T, Jaenicke C. PDR for Herbal Medicines. 1st ed. Montvale, NJ: Medical Economics Company, Inc., 1998.

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 Swamp Milkweed and Phenylephrine Together: Common Questions

Is it safe to take Swamp Milkweed with Phenylephrine?
We do not list a known interaction between Swamp Milkweed and Phenylephrine. 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 Swamp Milkweed and Phenylephrine have any of the same side effects?
Yes — our sources link each of them separately to 2 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 Swamp Milkweed and Phenylephrine combination checked?
Interactions in our licensed database are recorded against drug classes. Phenylephrine is filed under 5 classifications, and Swamp Milkweed has documented interactions with 7 drug classes — none of Phenylephrine'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 Swamp Milkweed interact with any other medications?
Yes. Swamp Milkweed has 156 documented drug interactions in our database — Phenylephrine 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 Phenylephrine interact with any supplements?
Yes. Phenylephrine has documented interactions with 81 supplements in our database — Swamp Milkweed is not one of them. The Phenylephrine 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

Swamp Milkweed monograph Uses, safety profile, and every drug interaction in one place Phenylephrine drug information The full plain-English guide to this medication Phenylephrine supplement interactions Every supplement checked against Phenylephrine, 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 Phenylephrine and Swamp Milkweed?

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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.