Drug & supplement interaction

Glycerol + 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 Glycerol 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

Glycerol 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 Glycerol 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.

Worth understanding: our licensed dataset holds no drug-interaction record for Glycerol at all — not against Phenylephrine, and not against any other medication we track. This verdict therefore rests on the absence of any recorded data, not on research that looked at this combination and found nothing. We cannot rule an interaction out.

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.

Glycerol safety at a glance

Glycerol overall Use caution Generally well tolerated in normal amounts, but large oral doses can cause stomach upset and dehydration concerns.
Pregnancy Use caution Topical and food-amount use is likely fine, but talk to your doctor before using medicinal doses.
Breastfeeding Use caution Little specific safety data exists, so check with your doctor before using larger medicinal amounts.

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

Still wondering about combining Phenylephrine and Glycerol? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
What to actually watch for

No Interaction Found — But Data Suggests Glycerol 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

    Glycerol

    “Orally, glycerol can cause mild headache and dizziness (15,2475).”

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

    2 sources cited
    1. 15. McEvoy GK, ed. AHFS Drug Information. Bethesda, MD: American Society of Health-System Pharmacists, 1998.
    2. 2475. Wagner DR. Hyperhydrating with glycerol: implications for athletic performance. J Am Diet Assoc 1999;99:207-12. PubMed

    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 ›

  • Nausea / Vomiting reported in 7.6% of FDA reports for Phenylephrine Additional detail

    Glycerol

    “Orally, glycerol can cause bloating, nausea, vomiting, thirst, and diarrhea (15,2475).”

    Glycerol · Natural Medicines adverse-effect record, reported in diarrhea.

    2 sources cited
    1. 15. McEvoy GK, ed. AHFS Drug Information. Bethesda, MD: American Society of Health-System Pharmacists, 1998.
    2. 2475. Wagner DR. Hyperhydrating with glycerol: implications for athletic performance. J Am Diet Assoc 1999;99:207-12. PubMed

    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 ›

Reported for Glycerol but not commonly for Phenylephrine: a stroke or mini-stroke, dizziness, hives and diarrhea.

Effects for Phenylephrine come from the ADVERSE REACTIONS section of its FDA label; effects for Glycerol 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.

Overlapping uses

What Phenylephrine Is Prescribed For, and What Glycerol Has Been Studied For

These two come up together because they touch the same health topic — not because they do the same job. Phenylephrine is a prescription medicine with approved uses on its FDA label. Glycerol is a supplement: what follows is what researchers have looked at it for, and how strong that evidence is.

Phenylephrine is prescribed for: 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.

Read the rest of what Phenylephrine is prescribed for

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.

Glycerol has been studied for:

  • Common cold studied, not established Glycerol has been studied for this. Natural Medicines rates the evidence: Insufficient Reliable Evidence To Rate Read what the research shows

    Glycerol for common cold

    Topical glycerol has only been evaluated in combination with other ingredients; its effect when used alone is unclear.

Effectiveness ratings and the research summaries above are the verbatim record from the Natural Medicines database, which grades evidence from “Effective” down to “Insufficient Reliable Evidence To Rate”. A rating below the top of that scale means researchers have looked at it — not that it works, and never that it can stand in for a prescribed medicine. Do not stop or replace Phenylephrine on your own; if you are taking Glycerol for the same health topic, tell your prescriber, especially if the medicine is being adjusted to a target.

From our Q&A

Questions About Glycerol 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 Glycerol 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 Glycerol 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

One more smart check

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

We hold 775 real supplement products containing Glycerol, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Glycerol. Even though Glycerol itself has no known interaction with Phenylephrine, 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 Glycerol 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 Glycerol
Top 25%

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

29 days ago today
Medication Phenylephrine
Top 25%

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

What is Glycerol?

Glycerol
  • Constipation (laxative)
  • Dry skin (moisturizer)
  • Dry, irritated eyes
  • Sore throat (in lozenges)
  • Athletic hydration and endurance
  • Cough and chest congestion (in some syrups)

Glycerol (glycerin) is a sweet, syrupy compound made naturally in the body and widely used in foods, skin products, and medicines. It is well established as a laxative and a skin and eye moisturizer, while its use to boost athletic performance is less proven and is banned in sports because it can mask other substances. For most people it is well tolerated, but check with a pharmacist before using it medicinally, especially if you are pregnant, breastfeeding, or have a health condition.

Not applicable (a simple chemical compound, also made naturally in the body) · Oral liquid, syrup, rectal suppositories, enemas, eye drops, skin creams and lotions, throat lozenges, sports drinks

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

Glycerol: dosing

There is no single "standard" dose of glycerol because it depends entirely on the product and the reason for use. A glycerin suppository for constipation, an oral laxative solution, an eye drop, and a sports hydration drink all use very different amounts.The safest approach is to follow the directions on the product label or your healthcare provider's instructions.

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

Read the full Glycerol 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 & Glycerol

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

0Major
0Moderate
0Minor
2,829No known interaction
2,829 No interaction
No interaction 2,829 drugs checked — show the list

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

Showing the 60 most looked-up of 2,829 medications checked with no known interaction — see the full Glycerol list.

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

Glycerol References

The 8 references that drive our Glycerol 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. McEvoy GK, ed. AHFS Drug Information. Bethesda, MD: American Society of Health-System Pharmacists, 1998.
  2. Wagner DR. Hyperhydrating with glycerol: implications for athletic performance. J Am Diet Assoc 1999;99:207-12. PubMed
  3. Yu YL, Kumana CR, Lauder IJ, et al. Treatment of acute cortical infarct with intravenous glycerol. A double-blind, placebo-controlled randomized trial. Stroke 1993;24:1119-24. PubMed
  4. Frei A, Cottier C, Wunderlich P, Ludin E. Glycerol and dextran combined in the therapy of acute stroke. A placebo-controlled, double-blind trial with a planned interim analysis. Stroke 1987;18:373-9. PubMed
  5. Balaskas E, Szepietowski JC, Bessis D, Ioannides D, Ponticelli C, Ghienne C, Taberly A, Dupuy P. Randomized, double-blind study with glycerol and paraffin in uremic xerosis. Clin J Am Soc Nephrol. 2011 Apr;6(4):748-52. PubMed
  6. Blanchet-Bardon C, Tadini G, Machado Matos M, Delarue A. Association of glycerol and paraffin in the treatment of ichthyosis in children: an international, multicentric, randomized, controlled, double-blind study. J Eur Acad Dermatol Venereol. 2012 Aug;26 PubMed
  7. Kajita N, Kanamori K, Yamamoto S, Yoshida K. Generalized Urticaria Caused by a Glycerin Enema in an Infant. J Investig Allergol Clin Immunol 2022;32(4):318-319. PubMed
  8. Suzuki R, Fukuyama K, Miyazaki Y, Namiki T. Contact urticaria syndrome and protein contact dermatitis caused by glycerin enema. JAAD Case Reports. 2016;2:108-10. 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 Glycerol and Phenylephrine Together: Common Questions

Is it safe to take Glycerol with Phenylephrine?
We do not list a known interaction between Glycerol 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 Glycerol and Phenylephrine 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.
Are Glycerol and Phenylephrine used for the same thing?
They overlap in purpose, which usually means the real question is whether you need both rather than whether they are safe together. This page lists the shared uses and how strong the evidence is for Glycerol in each. That is a conversation for your prescriber, especially if Phenylephrine is being adjusted to a target.
Does Phenylephrine interact with any supplements?
Yes. Phenylephrine has documented interactions with 81 supplements in our database — Glycerol 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

Glycerol 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 8 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Phenylephrine and Glycerol?

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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.