Drug & supplement interaction

Forsythia + Cimetidine

Cimetidine brand names: Tagamet HB, Tagamet, Cimetidine Injection.

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 Forsythia and Cimetidine 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.

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Interaction report

Forsythia and Cimetidine

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 Cimetidine and Forsythia 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.

Forsythia safety at a glance

Forsythia overall Use caution Generally used short-term in traditional medicine, but human safety data are limited.
Pregnancy Avoid Not enough safety data; avoid during pregnancy.
Breastfeeding Avoid Not enough safety data; best avoided while breastfeeding.

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

Still wondering about combining Cimetidine and Forsythia? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Cimetidine

Interactions in our licensed database are recorded against drug classes, not just single drug names. Cimetidine is filed under 9 classifications — including h2-blockers, cytochrome p450 2c9 (cyp2c9) inhibitors, cytochrome p450 1a2 (cyp1a2) inhibitors. Forsythia has documented interactions with 2 drug classes — the most serious being anticoagulant/antiplatelet drugs (moderate) and azithromycin (zithromax) (minor) — and none of Cimetidine’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

Forsythia Does Interact With Other Medications

Forsythia has 122 moderate, 1 minor known drug interactions in our database — Cimetidine isn’t one of them. If you take anything else, check it against the full list below.

Moderate 122 Minor 1 No known interaction 2,707 (incl. Cimetidine)
Taking anything else?

Check Another of Your Medications Against Forsythia

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

What to actually watch for

What Cimetidine’s Own FDA Label Lists

This is not an interaction — none of it involves Forsythia. These are the most notable effects listed in the ADVERSE REACTIONS section of Cimetidine’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.

  • Trouble passing urine Worth acting on
  • A slow heartbeat Worth acting on
  • Hallucinations Worth acting on
  • Pancreatitis Worth acting on
  • Confusion Worth acting on
  • A severe skin reaction Worth acting on
  • Low mood Worth acting on
  • A low platelet count Worth acting on
  • Kidney problems Worth acting on
  • Anemia Worth acting on

Showing the 10 most notable of 28 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 Cimetidine. Read the label on DailyMed › Forsythia’s licensed record lists no adverse effects our clinical vocabulary could match, so there is no Forsythia side to compare — that is a limit of the record, not a statement that Forsythia has no side effects.

From our Q&A

Questions About Forsythia or Cimetidine

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

This page covers Forsythia only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Cimetidine page lists 95 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Pu-erh Tea (major), St. John's Wort (major), Adrafinil (moderate) and African Wild Potato (moderate).

By severity: 3 major · 63 moderate · 29 minor.

Open the Cimetidine interaction page

One more smart check

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

We hold 355 real supplement products containing Forsythia, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Forsythia. Even though Forsythia itself has no known interaction with Cimetidine, 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 Forsythia and Cimetidine 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 Forsythia
Top 25%

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

29 days ago today
Medication Cimetidine
Top half

#1,190 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 Forsythia reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 20, 2026. The Forsythia and Cimetidine records this page draws on were last updated June 20, 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 Forsythia

What is Forsythia?

  • Colds and flu symptoms
  • Sore throat
  • Fever
  • Inflammation
  • Antimicrobial support

Forsythia is a traditional Chinese herb, used mainly for cold and flu symptoms and as part of multi-herb formulas. Most evidence comes from laboratory, animal, and traditional use rather than strong human studies, so its real-world benefits remain unproven. Talk to your pharmacist or doctor before using it, especially if you are pregnant, breastfeeding, or taking other medicines.

Forsythia suspensa · Oleaceae · Dried fruit (and sometimes leaves) · Dried fruit, teas, decoctions, capsules, and herbal formulas

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

Forsythia: dosing

There is no well-established standardized dose for forsythia. Traditional preparations use the dried fruit in decoctions, often as part of a multi-herb formula, and amounts vary by product and practitioner.If you use a commercial supplement, follow the directions on the product label and do not exceed the recommended amount.

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

Read the full Forsythia monograph & all interactions
Medication

About Cimetidine

What Is Cimetidine Used For?

Brand names: Tagamet HB, Tagamet, Cimetidine Injection

Cimetidine tablets sold over the counter — including brands like Acid Controller, Acid Reducer, Basic Care Acid Reducer, Equate Cimetidine, and cimetidine 200 — are used to relieve heartburn associated with acid indigestion and sour stomach, and to prevent heartburn brought on by eating or drinking certain foods and beverages.

Prescription-strength cimetidine tablets and Cimetidine Hydrochloride Oral Solution are used for more serious conditions: short-term treatment of active duodenal ulcers (ulcers in the upper small intestine) and benign gastric ulcers (stomach ulcers), maintenance therapy to keep duodenal ulcers from coming back, healing of erosive GERD (acid reflux that has damaged the lining of the esophagus), and treatment of conditions that cause the stomach to make too much acid — such as Zollinger-Ellison Syndrome, systemic mastocytosis, and multiple endocrine adenomas.

Most-Reported Side Effects for Cimetidine

From FAERS, the FDA’s public side-effect reporting system (0 reports, all brands). Reports are voluntary and are not proof the drug caused the effect.

Chronic kidney disease 1,317 reports
Acute kidney injury 747 reports
Renal failure 715 reports
Nausea 700 reports
Fatigue 614 reports
See full Cimetidine drug information
Keep checking

Other Drugs & Forsythia

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

0Major
122Moderate
1Minor
2,706No known interaction
122 Moderate 1 Minor 2,706 No interaction
Moderate

122 interactions

Showing 60 of 122 moderate interactions — see all 122 on the Forsythia page.

Minor

1 interaction

No interaction 2,706 drugs checked — show the list

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

Showing the 60 most looked-up of 2,706 medications checked with no known interaction — see the full Forsythia list.

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

Forsythia References

The 3 references that drive our Forsythia 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. Kong XT, Fang HT, Jiang GQ, et al. Treatment of acute bronchiolitis with Chinese herbs. Arch Dis Child 1993;68:468-71. PubMed
  2. Iwakami S, Wu JB, Ebizuka Y, Sankawa U. Platelet activating factor (PAF) antagonists contained in medicinal plants: lignans and sesquiterpenes. Chem Pharm Bull (Tokyo) 1992;40:1196-8. PubMed
  3. Li XG, Ni J, Shen S, Wang XP, Tian JC. Pharmacokinetic interaction of Forsythia suspensa extract and azithromycin injection after single and co-intravenous administration in rats. Chin J Nat Med 2020;18(3):234-240. 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 Forsythia and Cimetidine Together: Common Questions

Is it safe to take Forsythia with Cimetidine?
We do not list a known interaction between Forsythia and Cimetidine. 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 Forsythia and Cimetidine combination checked?
Interactions in our licensed database are recorded against drug classes. Cimetidine is filed under 9 classifications, and Forsythia has documented interactions with 2 drug classes — none of Cimetidine'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 Forsythia interact with any other medications?
Yes. Forsythia has 123 documented drug interactions in our database — Cimetidine 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 Cimetidine interact with any supplements?
Yes. Cimetidine has documented interactions with 95 supplements in our database — Forsythia is not one of them. The Cimetidine 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

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

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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.