Drug & supplement interaction

Phenpromethamine + Metronidazole

Metronidazole brand names: Flagyl, Protostat, Metronidazole, Nidazol, Trikacide, and others.

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

We found no known interaction between Phenpromethamine and Metronidazole 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

Phenpromethamine and Metronidazole

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 Metronidazole and Phenpromethamine 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.

Phenpromethamine safety at a glance

Phenpromethamine overall Avoid This is an unapproved synthetic stimulant that should not be used as a supplement.
Pregnancy Possibly Unsafe When used orally. Certain stimulants, especially when used in combination with other stimulants or intensive exercise, have been associated with cardiovascular... Read the full pregnancy detail
Breastfeeding Possibly Unsafe When used orally. Certain stimulants, especially when used in combination with other stimulants or intensive exercise, have been associated with cardiovascular... 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 Metronidazole and Phenpromethamine? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Metronidazole

Interactions in our licensed database are recorded against drug classes, not just single drug names. Metronidazole is filed under 8 classifications — including cytochrome p450 2c9 (cyp2c9) inhibitors, qt interval-prolonging drugs, cytochrome p450 3a4 (cyp3a4) inhibitors. Phenpromethamine has documented interactions with 1 drug class — the most serious being stimulant drugs (moderate) — and none of Metronidazole’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

Phenpromethamine Does Interact With Other Medications

Phenpromethamine has 172 moderate known drug interactions in our database — Metronidazole isn’t one of them. If you take anything else, check it against the full list below.

Moderate 172 No known interaction 2,658 (incl. Metronidazole)
Taking anything else?

Check Another of Your Medications Against Phenpromethamine

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

What to actually watch for

What Metronidazole’s Own FDA Label Lists

This is not an interaction — none of it involves Phenpromethamine. These are the most notable effects listed in the ADVERSE REACTIONS section of Metronidazole’s own FDA label, for the medication by itself. Knowing the drug’s own list makes it easier to work out the likely cause if something new turns up while you take both. 10 of them are worth acting on rather than waiting out — marked below.

  • Hearing loss Worth acting on
  • Pain or burning when passing urine Worth acting on
  • Unsteadiness Worth acting on
  • Pancreatitis Worth acting on
  • Fainting Worth acting on
  • An irregular heartbeat Worth acting on
  • Confusion Worth acting on
  • A severe skin reaction Worth acting on
  • Seizures Worth acting on
  • Low mood Worth acting on

Showing the 10 most notable of 35 label-listed effects — ranked by how unusual each one is across medicines generally, with serious effects weighted up.

From the ADVERSE REACTIONS section of the FDA label for Metronidazole. Read the label on DailyMed › Where a percentage is shown, it is the share of 64,630 voluntary FDA FAERS reports for Metronidazole that mention that effect — a reporting proportion, not an incidence rate and not evidence the drug caused it. Phenpromethamine’s licensed record lists no adverse effects our clinical vocabulary could match, so there is no Phenpromethamine side to compare — that is a limit of the record, not a statement that Phenpromethamine has no side effects.

Special populations

Phenpromethamine in Pregnancy & Breastfeeding

Pregnancy And Lactation Possibly Unsafe

When used orally. Certain stimulants, especially when used in combination with other stimulants or intensive exercise, have been associated with cardiovascular events such as stroke and cardiac arrest. 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 Phenpromethamine or Metronidazole

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

This page covers Phenpromethamine only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Metronidazole page lists 83 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), American Hellebore (major), Arsenic (major), Cesium (major) and Ephedra (major).

By severity: 7 major · 63 moderate · 13 minor.

From our pharmacist’s overview on the Metronidazole page

“Metronidazole (Flagyl) can stretch the heart's QT interval on its own, and most of the seven major-rated interactions among its 83 flagged supplement ingredients do the same thing, so I read this list with more wariness than most antibiotics earn. Grapefruit and ephedra stand out for adding to that heart-rhythm risk, while activated ch…”

Reviewed by 2 · Jul 18, 2026

Open the Metronidazole interaction page

How much people look this up

Where Phenpromethamine and Metronidazole 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 Phenpromethamine
Steady interest

#1,143 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Metronidazole
Top 25%

#329 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 Phenpromethamine reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 20, 2026. The Phenpromethamine and Metronidazole records this page draws on were last updated June 22, 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 Phenpromethamine

What is Phenpromethamine?

  • Nasal decongestion (historical)
  • Stimulant effects (misuse)
  • Pre-workout 'energy' (illegally added to some products)

Phenpromethamine is a synthetic stimulant drug, not a herb or legitimate dietary supplement. It has been found illegally added to some sports and weight-loss supplements, and it is not approved for use in the United States. You should avoid any product that lists it as an ingredient and talk to a pharmacist or doctor.

Not applicable; phenpromethamine is a synthetic chemical, not a plant part · Historically found as a nasal inhaler; not a legitimate dietary supplement ingredient

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

Phenpromethamine: dosing

There is no established or recommended dose of phenpromethamine for supplement use. It is not an approved supplement ingredient, and any amount found in products is unregulated and potentially unsafe.Because the amount in spiked products is unknown and uncontrolled, no dose can be considered safe. The best advice is to avoid products that contain it entirely.

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

Read the full Phenpromethamine monograph & all interactions
Medication

About Metronidazole

What Is Metronidazole Used For?

Brand names: Flagyl, Protostat, Metronidazole, Nidazol, Trikacide, MetroGel, Flagyl IV, Metronidazole Redi-Infusion, Flagyl IV RTU, Metro IV, Anabact, Metrosa, Metrotop, Noritate, Rozex Cream, Rozex Gel, Zyomet, Likmez

Metronidazole treats three main types of infections. It's used for trichomoniasis (a sexually transmitted parasitic infection), amebiasis (an intestinal or liver infection caused by a parasite), and serious anaerobic bacterial infections — infections caused by bacteria that thrive without oxygen, which can affect the abdomen, skin, bones, lungs, and other areas.

Because sexual partners can pass trichomoniasis back and forth, both partners are typically treated at the same time, even if one has no symptoms.

Most-Reported Side Effects for Metronidazole

From FAERS, the FDA’s public side-effect reporting system (64,630 reports, all brands). Reports are voluntary and are not proof the drug caused the effect.

Nausea 4,812 reports
Diarrhea 4,197 reports
Vomiting 3,393 reports
Fever 3,294 reports
Drug hypersensitivity 3,160 reports
See full Metronidazole drug information
Keep checking

Other Drugs & Phenpromethamine

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

0Major
172Moderate
0Minor
2,657No known interaction
172 Moderate 2,657 No interaction
Moderate

172 interactions

Showing 60 of 172 moderate interactions — see all 172 on the Phenpromethamine page.

No interaction 2,657 drugs checked — show the list

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

Showing the 60 most looked-up of 2,657 medications checked with no known interaction — see the full Phenpromethamine list.

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

Phenpromethamine References

The 2 references that drive our Phenpromethamine 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. Venhuis B, Keizers P, van Riel A, de Kaste D. A cocktail of synthetic stimulants found in a dietary supplement associated with serious adverse events. Drug Test Anal. 2014 Jun;6(6):578-81. doi: 10.1002/dta.1664. Epub 2014 May 6. PubMed
  2. Cohen PA, Travis JC, Vanhee C, Ohana D, Venhuis BJ. Nine prohibited stimulants found in sports and weight loss supplements: deterenol, phenpromethamine (Vonedrine), oxilofrine, octodrine, beta-methylphenylethylamine (BMPEA), 1,3-dimethylamylamine (1,3-DMA

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 Phenpromethamine and Metronidazole Together: Common Questions

Is it safe to take Phenpromethamine with Metronidazole?
We do not list a known interaction between Phenpromethamine and Metronidazole. 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 Phenpromethamine and Metronidazole combination checked?
Interactions in our licensed database are recorded against drug classes. Metronidazole is filed under 8 classifications, and Phenpromethamine has documented interactions with 1 drug class — none of Metronidazole'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 Phenpromethamine interact with any other medications?
Yes. Phenpromethamine has 172 documented drug interactions in our database — Metronidazole 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 Metronidazole interact with any supplements?
Yes. Metronidazole has documented interactions with 83 supplements in our database — Phenpromethamine is not one of them. The Metronidazole 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

Phenpromethamine monograph Uses, safety profile, and every drug interaction in one place Metronidazole drug information The full plain-English guide to this medication Metronidazole supplement interactions Every supplement checked against Metronidazole, 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 2 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Metronidazole and Phenpromethamine?

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.