Herb & supplement monograph

Forsythia Drug Interactions, Uses, Effectiveness, Safety & More

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS ·Updated June 2026

What is this page for?

First and foremost: how Forsythia interacts with medications. The heart of this page is the interaction list — every drug Forsythia is known to interact with, and how serious each one is.

But these pages have grown well beyond that into a full monograph — what Forsythia is, what people use it for and how strong the evidence is, its safety and side effects, and answers to the questions we’re asked most — written and reviewed by the clinical staff at HelloPharmacist. It’s educational information from our licensed clinical databases, not medical advice, and we don’t sell or endorse products. Our editorial policy

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Forsythia Drug Interactions: The Bottom Line

From the HelloPharmacist Editorial Team · Updated July 2026

Based on the available evidence, the overall risk of a clinically significant Forsythia drug interaction appears low for most people. None of the listed interactions are rated major, and the concerns behind them come from lab and animal research rather than studies in people.

Interactions deserving the most attention

The interaction that deserves the most attention involves anticoagulant and antiplatelet medications, such as warfarin, aspirin, and clopidogrel. In theory, forsythia might slow platelet clumping, which could add to the blood-thinning effect of these drugs and raise bleeding risk. That said, this effect has not been shown to occur in humans, so it remains a precaution rather than a proven problem. A minor animal-study finding with azithromycin suggests the two may affect how each other is cleared from the body, but its meaning for people is unclear.

What the rest of the list means

Forsythia appears alongside a long list of medications, but that number mostly reflects one theoretical concern applied across every blood-thinning drug. It does not mean each combination is harmful. In fact, the predicted effects have not been confirmed in human studies, so most of these listings are cautious placeholders rather than documented problems.

Check your medications against Forsythia

Based on HelloPharmacist’s Forsythia interaction data and reviewed under our editorial standards.

Interaction report

Drugs that interact with Forsythia

123 medications have a known interaction with Forsythia, graded by severity. Select any drug for the full evidence-based detail.

Don’t want to scroll the list? Just ask.

Tell us the medications you take and we’ll check each one against Forsythia using our pharmacist-reviewed interaction data.

AI summaries are generated from our Forsythia interaction data for education only — always confirm with your pharmacist. How we use AI

2,830 drugs

Read The List Like a Pharmacist

What Severity, Likelihood & Evidence Mean

Severity — How Serious It Can Be

Major. Clinically significant; generally best avoided, or used only under direct professional supervision.
Moderate. May need monitoring, a dose adjustment, or separating the times you take each one.
Minor. Generally not clinically significant, but still worth noting and mentioning to your pharmacist.
No known interaction. Checked against our sources with nothing documented — not the same as proven safety.

Likelihood — How Well It’s Documented

Likely. Well-controlled human studies have demonstrated the likely existence of this interaction
Probable. Interaction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
Possible. Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists
Unlikely. Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans.

Where This Data Comes From

Interaction records are evidence-graded and sourced from the Natural Medicines database (TRC Healthcare), the same reference used by pharmacists and hospitals.
Each drug listed above links to the full report for that exact Forsythia combination — clinical detail, likelihood, evidence level, and citations.
Content is reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

The big picture

The kinds of drugs Forsythia affects

Every type of medication (drug category) Forsythia is known to interact with. Open any category for the detail — or search your exact drug in the checker above.

All 2 drug categories Forsythia interacts with

Anticoagulant/antiplatelet DrugsAzithromycin (zithromax)

Anticoagulant/Antiplatelet Drugs

Theoretically, taking forsythia with anticoagulant or antiplatelet drugs might increase the risk of bleeding due to decreased platelet aggregation. Forsythia might reduce platelet aggregation by inhibiting platelet activating factor. Some of these drugs include aspirin, clopidogrel (Plavix), dalteparin (Fragmin), enoxaparin (Lovenox), heparin, ticlopidine (Ticlid), warfarin (Coumadin), and others.

Likelihood Unlikely Evidence D

Azithromycin (Zithromax)

Theoretically, taking forsythia with azithromycin might increase the risk of adverse effects. Animal research in rats shows that taking a single dose of forsythia with azithromycin decreases the clearance and increases the area under the curve of both forsythiaside, a constituent of forsythia, and azithromycin. The mechanism of this interaction is not well understood.

Likelihood Unlikely Evidence D

Monograph

Forsythia: Uses, Safety & Side Effects

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS · Reviewed June 2026 ·

The bottom line

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.

Scientific name: Forsythia suspensa
Family: Oleaceae
Part used: Dried fruit (and sometimes leaves)
Common forms: Dried fruit, teas, decoctions, capsules, and herbal formulas

People commonly use it for

Colds and flu symptoms
Sore throat
Fever
Inflammation
Antimicrobial support

Popular and traditional uses — not proof it works. See “Uses & effectiveness” below for the evidence.

Safety at a glance

OverallUse caution

Generally used short-term in traditional medicine, but human safety data are limited.

PregnancyBest avoided

Not enough safety data; avoid during pregnancy.

BreastfeedingBest avoided

Not enough safety data; best avoided while breastfeeding.

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

Jump to a section

Overview

Forsythia comes from the fruit of Forsythia suspensa, a flowering shrub in the olive family. It is native to East Asia and is widely grown as an ornamental plant for its bright yellow spring flowers. In traditional Chinese medicine the dried fruit is called "Lian Qiao."

Forsythia is rarely used by itself. It is most often combined with other herbs in classic formulas used for colds, fevers, and sore throats. Today it is sold as dried fruit, teas, and capsules, and it appears in many combination products marketed for immune or respiratory support.

How it works

Forsythia fruit contains several plant compounds that researchers have studied, including forsythiaside, phillyrin, lignans, and flavonoids. In laboratory tests these compounds have shown antioxidant, anti-inflammatory, and antimicrobial effects.

The proposed idea is that these compounds may help calm inflammation and slow the growth of certain bacteria and viruses. It is important to remember that most of this work is based on test-tube and animal research. Results in a lab do not always carry over to the human body, so these mechanisms remain theories rather than proven actions.

Effectiveness

Does Forsythia work?

Here’s what the research actually shows for each use — graded by Natural Medicines and reviewed by Dr. Brian Staiger, PharmD.

Evidence overview · 1 use evaluated

1 Insufficient evidence

How to read these evidence grades

Natural Medicines’ 7-point scale. We show each rating’s label word-for-word.

1EffectiveStrong, consistent evidence it works.

2Likely EffectiveGood evidence, though not yet conclusive.

3Possibly EffectiveSome evidence suggests a benefit.

4Possibly IneffectiveSome evidence it may not help.

5Likely IneffectiveFairly strong evidence it doesn’t help.

6IneffectiveStrong evidence it doesn’t work.

7Insufficient Reliable Evidence to RateToo little research to say either way.

For Forsythia, current evidence isn’t strong enough to rate any specific use. The conditions it has been studied for are listed below.

Also studied for 1 condition — evidence insufficient to rate

Insufficient Reliable Evidence To Rate Bronchiolitis

Rating & evidence shown verbatim from Natural Medicines

Preliminary clinical research suggests a combination of forsythia, honeysuckle, and Baikal skullcap given intravenously might decrease the duration of symptoms of bronchiolitis in children with respiratory syncytial virus infection.

Sources Ref 12613

Source & disclaimer. Effectiveness ratings and evidence summaries are provided by Natural Medicines (Therapeutic Research Center) and shown as licensed. Where Natural Medicines hasn’t rated a use, HelloPharmacist’s pharmacists may add their own reviewed rating and evidence (each such entry is labeled). This is educational information, not medical advice — talk with your pharmacist or doctor before starting, stopping, or changing a supplement.

Safety & precautions

Forsythia has a long history of traditional use and is generally taken for short periods. Still, modern safety data in humans are limited, so it is hard to be certain about long-term use or high doses.

People with a known allergy to forsythia or related plants should avoid it. Those with chronic health conditions, or anyone taking prescription medicines, should check with a pharmacist or doctor first.

Pregnancy and breastfeeding: Because there is not enough reliable safety information, it is best to avoid forsythia if you are pregnant or breastfeeding.

Quality can also vary between products. Herbal supplements are not tightly regulated, so choose products from reputable companies that test for purity.

Side effects

Forsythia is generally well tolerated when used short-term in traditional amounts. The most commonly reported side effects are mild and digestive, such as nausea, stomach upset, or diarrhea.

Allergic reactions are possible, especially in people sensitive to plants in the olive family. Stop using it and seek medical care if you notice rash, swelling, or trouble breathing. Because human safety studies are limited, report any unusual symptoms to your healthcare provider.

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. Because the right dose is not clearly defined, it is wise to start low and check with a pharmacist or doctor, especially if you take other medicines or have a health condition.

References & further reading

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.

Kong XT, Fang HT, Jiang GQ, et al. Treatment of acute bronchiolitis with Chinese herbs. Arch Dis Child 1993;68:468-71. PubMed
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
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

Keep reading

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.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

Brand directory

Brands that make products with Forsythia

55 brands in our database make a supplement containing Forsythia.

21st Century 798 products Airborne 104 products Airborne Everyday 1 product Airborne Kids 1 product Airborne Original 14 products Airborne Plus 6 products BIOVEA 1,494 products Blisque 16 products CV Sciences 51 products Dr. Xu 1 product Energetix 283 products Equate 143 products Farlong 12 products GinSen 1 product Guang Ci Tang 121 products Hawaii Pharm 4,726 products Health Concerns 444 products Herbal Terra 3,138 products L.A. Naturals 201 products Merry Clinic 33 products Metagenics 1,072 products Min Shan 86 products Natura Health Products 1 product Natural Factors 1,332 products

Product directory

Supplement products with Forsythia

355 products in our database contain Forsythia. Open any to see its full ingredient list and every drug interaction we check.

Pharmacist Counseling Corner

Forsythia: Common Questions

What is Forsythia used for, and does it work?

People use Forsythia for a range of reasons, but according to the Natural Medicines database the current clinical evidence is insufficient to confirm it works for the specific conditions it has been studied for. See the graded list on this page, and talk to your pharmacist or doctor before relying on it for any condition.

Does Forsythia interact with prescription medications?

Yes. We list 123 medications with a known interaction with Forsythia. Use the checker above to see how Forsythia interacts with a specific drug.

How are Forsythia interactions rated?

Each interaction is graded major, moderate, or minor based on how clinically significant it is and the strength of the evidence behind it. Major interactions are the most serious and are best avoided, or used only under close professional supervision.

Is it safe to take Forsythia with my medications?

It depends on the specific medication. Some combinations are fine, while others call for monitoring, timing changes, or should be avoided. Check your exact drug above and confirm with your pharmacist or doctor before starting, stopping, or changing anything.

Where does this Forsythia interaction information come from?

Our interaction data is built on the Natural Medicines database — an evidence-graded reference for vitamins, herbs, and supplements — and is reviewed by licensed HelloPharmacist pharmacists, who may add clinical context.

What is Forsythia used for?

It is mainly used in traditional medicine for cold and flu symptoms, sore throat, fever, and inflammation, often combined with other herbs. Strong human evidence for these uses is lacking.

Is Forsythia safe to take?

It is generally well tolerated short-term in traditional doses, but human safety data are limited. Talk to your pharmacist or doctor before using it, especially if you have a health condition or take other medicines.

Can I take Forsythia while pregnant or breastfeeding?

There is not enough reliable safety information, so it is best to avoid Forsythia during pregnancy and breastfeeding.

Does Forsythia really help fight colds?

Some lab and animal studies suggest antimicrobial and anti-inflammatory effects, but solid human evidence is lacking. It should be viewed as a traditional remedy, not a proven cold treatment.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Keep exploring

Products that contain Forsythia

A rotating sample of real supplements in our database that list Forsythia — open any to see its full ingredients and every drug interaction we check.

See all 355 products with Forsythia →

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