Pei Lan (Eupatorium)

Chinese Herb Actions

Chinese Herb Dosage

• What is the typical dosage of Pei Lan?

  Roughly 3–10 g in decoction, with the dose doubled when fresh herb is used — this site records 5–10 g from one reference and 3–9 g from another, both noting the fresh-herb doubling. The part used is the aerial portion (herb).

  • Aromatic herb handling — like other acrid aromatic damp-transforming herbs it is volatile-oil-bearing, and prolonged cooking is traditionally avoided so the aromatic fraction is not driven off.
  • Dose ceiling matters here — see the toxicity section: chronic or high-dose use is where the documented pyrrolizidine alkaloid content becomes a reference concern.

  Source: the site’s own dosage record (two published references); chronic-use caution context from PMID 33774095, DOI 10.1016/j.fct.2021.112151. Reference only — not a prescription.

Chinese Herb Contraindications & Cautions

• Are there cautions for Pei Lan?

  This site’s record lists no traditional contraindications, but there is a modern one worth knowing: Eupatorium fortunei has documented pyrrolizidine alkaloid content, so short-term use at customary doses is the framing supported by the evidence, and prolonged or high-dose use is not. As an acrid, drying, aromatic herb it is also generally regarded as unsuitable where yin or fluids are already depleted.

  • Pyrrolizidine alkaloids (reference note) — see the toxicity section. This is a species-level finding, not a genus generalisation, and it is the main reason to use this herb under professional supervision rather than casually or long-term.
  • Pregnancy — not documented as contraindicated in the sources we could verify, but pyrrolizidine-alkaloid-bearing plants are conventionally avoided in pregnancy and lactation as a general precaution. Noted as a precaution, not as a sourced traditional contraindication.

  Source: the site’s own cautions record; alkaloid context from PMID 33774095 and PMID 41976178, PMC 13075190. Reference note, not a safety guarantee.

Chinese Herb Toxicity & Overdose

• Does Pei Lan contain pyrrolizidine alkaloids? Is it safe?

  Yes — pyrrolizidine alkaloids are documented in Eupatorium fortunei specifically, not merely in the genus. But the published picture is genuinely mixed on how much this matters at customary doses, and we report both sides rather than resolving them. Pyrrolizidine alkaloids are a class of plant constituents associated with liver injury with sustained exposure.

  • What was found — a 2021 analysis using reference standards identified eight pyrrolizidine alkaloids in E. fortunei, with intermedine N-oxide and lycopsamine N-oxide the most abundant. Total content varied enormously between batches: 0.18 to 61.81 micrograms per gram across 30 herb batches, and 0.86 to 36.96 micrograms per gram across four commercial finished products.
  • How the authors read it — that study concluded short-term intake seemed unlikely to cause acute toxic effects, but that chronic use warranted caution, and that for the majority of batches the exposure would exceed the European Medicines Agency’s reference intake limit of 1.0 micrograms of pyrrolizidine alkaloid per day for adults. Three of the identified alkaloids also reduced viability of cultured neural progenitor cells at 30 micromolar.
  • Animal evidence for the isolated alkaloid fraction — a 2022 study dosed mice with the total alkaloid fraction of E. fortunei (of which pyrrolizidine alkaloids made up over 92%) and found reduced body and liver weight, raised liver enzymes, and histological liver damage. This tested a concentrated alkaloid extract, not the whole herb or a decoction.

  A real conflict in the literature. An earlier comparative study (1987) measured pyrrolizidine alkaloid content across several Eupatorium species including E. fortunei and found very low concentrations relative to known hepatotoxic plants, and found no accumulation of hepatic pyrrolic metabolites in mice given either single doses or chronic administration of Eupatorium decoctions. A 2026 review likewise describes the herb as generally considered safe while noting that certain pyrrolizidine alkaloids present potential hepatotoxic risk that can be managed by dose control. Reading these together: the presence of pyrrolizidine alkaloids in this species is established; the magnitude of real-world risk from customary decoction use is not settled, and the batch-to-batch variation is itself part of why. We state that openly rather than either asserting the hazard or ignoring it.

  Sources: PMID 33774095, DOI 10.1016/j.fct.2021.112151 (alkaloid quantification, risk assessment, neural progenitor cells); PMID 36356015, PMC 9698670, DOI 10.3390/toxins14110765 (mouse hepatotoxicity of the total alkaloid fraction); PMID 3687841, DOI 10.1142/S0192415X87000084 (low alkaloid content, no pyrrolic metabolite accumulation); PMID 41976178, PMC 13075190, DOI 10.3390/molecules31071137 (review, toxicology summary). Neutral reference facts — not preparation or dosing guidance.

Herb-Drug Interactions

• No well-established clinical herb–drug interactions are documented for Pei Lan. Given the documented pyrrolizidine alkaloid content, practitioner awareness is reasonable where liver function is already compromised or where other hepatically stressing medication is in use — this is precautionary reasoning from the constituent literature, not a demonstrated clinical interaction. Patients taking prescription medication should tell their prescriber about any herbal use.

  Source: precautionary inference from PMID 33774095 and PMID 36356015. Flagged for practitioner confirmation.

Western / Biomedical Research

Chinese Herb Clinical Studies & Research

Provided as research context — a summary of published biomedical study, not a therapeutic or medical claim.

• Is there modern research on Pei Lan (Eupatorium fortunei)?

  Yes — a substantial chemistry and preclinical pharmacology literature, but no clinical trials for the traditional indications. A 2026 systematic review counted 162 compounds identified to date, with thymol derivatives and benzofurans the most prominent bioactive classes, alongside terpenoids, alkaloids, fatty acids and volatile-oil constituents.

  • Antiviral — E. fortunei extract and its components increased antiviral immune responses against RNA viruses in laboratory models.
  • Anti-inflammatory — chemical fractionation of the aerial parts yielded a series of lipids, a lignan (brachangobinan A) and monoterpenes; the lignan was the most active in a nitric-oxide inhibition assay and suppressed pro-inflammatory factors via NF-kappa-B signalling in cell models.
  • Cytotoxicity — thymol derivatives isolated from the aerial parts have been evaluated against cancer cell lines; two newly described thymol derivatives showed weak activity (IC50 above 50 micromolar) against four lines, so this is a chemistry finding rather than an anticancer claim.
  • Reported activity range — the review summarises anti-cancer, antiviral, antifungal, anti-inflammatory and anti-diabetic activity across the literature, and notes the same pyrrolizidine alkaloid toxicology discussed above.

  All of this is laboratory and animal work; none of it is clinical evidence for the traditional indications.

  Sources: PMID 41976178, PMC 13075190, DOI 10.3390/molecules31071137 (systematic review, botany/phytochemistry/pharmacology/toxicology); PMID 28824435, PMC 5541272, DOI 10.3389/fphar.2017.00511 (antiviral immune responses); PMID 37832878, DOI 10.1016/j.fitote.2023.105700 (anti-inflammatory constituents); PMID 36175160, DOI 10.1080/14786419.2022.2124247 (thymol derivatives). Research context, not a therapeutic claim.

Chinese Herb Notes

• What is the difference between Pei Lan and Ze Lan?

  They are different plants with different actions, and the similar-sounding names are the only thing they share. Both are aromatic, which makes the confusion easier to fall into, but they belong to different categories.

  • Pei Lan — the aerial parts of Eupatorium fortunei (Asteraceae). Acrid and neutral; Spleen and Stomach. An aromatic herb that transforms dampness and releases summerheat.
  • Ze Lan — recorded on this site as the herb of Lycopus lucidus (a mint-family plant). Bitter, acrid, slightly warm and aromatic; Liver and Spleen. It is a blood-invigorating herb used for blood stasis, and is not a damp-transforming herb.
  • Practical upshot — a damp-obstructed middle burner calls for Pei Lan; a blood-stasis presentation calls for Ze Lan. They are not substitutes in either direction.

  How is Pei Lan different from Huo Xiang?

  Pei Lan and Huo Xiang are the classic pair in the aromatic damp-transforming category and are often used together. Both use acrid, aromatic qualities to transform dampness, release summerheat and rouse the Spleen. Pei Lan is the better fit for chest oppression with profuse thick, sticky saliva and a sweet taste in the mouth; Huo Xiang is the better fit for nausea and vomiting, and Huo Xiang additionally enters the Lung channel and has a stronger exterior-releasing aspect.

  Source: the site’s own records for Pei Lan, Ze Lan and Huo Xiang; botanical family placement per PMID 41976178, PMC 13075190. Cross-referenced against multiple online sources.