Forms, Dosing and Interactions

Two women can take a capsule labelled "chasteberry 400 mg" and a tablet labelled "chasteberry 20 mg" and the second one is the one with the trial behind it. That is not a typo — it is the single most confusing thing about buying this herb, and this page exists to sort it out.

What follows is practical: what the named extracts are and why they matter, how to read a label, the doses that have actually been tested, how and when to take it, what the side-effect profile really looks like from a systematic review rather than a marketing page, and the interactions that follow logically from a herb that acts on dopamine receptors. The interaction section is the one to read even if you skip the rest.

Table of Contents

1. Ze 440, BNO 1095, and Everything Else
2. How to Read a Chasteberry Label
3. Doses That Have Actually Been Tested
4. Tinctures, Teas and Whole Berries
5. How and When to Take It
6. Side Effects: What the Safety Review Found
7. Interactions: Dopamine Drugs
8. Contraception, HRT and IVF
9. Pregnancy and Breastfeeding
10. Who Should Not Take It, and When to Stop
11. Cost and Product Quality
12. Key Research Papers
13. Connections

Ze 440, BNO 1095, and Everything Else

Nearly all the credible clinical evidence for chasteberry comes from two named, standardised extracts. Knowing their names is the most useful shopping information on this page.

• Ze 440 — a dry ethanolic extract of the fruit produced in Switzerland, dosed as one tablet containing 20 mg of native extract. It is the extract used in the BMJ trial, in the dose-ranging study that established 20 mg as the right dose, in the Berger PMS study, and in the Japanese open-label study (marketed there as Prefemin). It is sold in various countries under names including Prefemin and Premular.
• BNO 1095 — a German extract corresponding to 40 mg of herbal drug per tablet, used in both Chinese randomised trials and marketed in Europe under names including Agnucaston and Agnolyt.

The 2019 meta-analysis makes the point in the sharpest possible way. Its authors applied the CONSORT reporting extension for herbal interventions, which simply requires a trial to describe its preparation well enough for the result to mean something. Out of 21 clinical trials of chasteberry, only three passed — and all three used Ze 440 or BNO 1095. Those three trials, covering 520 women, produced the relative risk of 2.57 for symptom remission. The other eighteen could not be used as efficacy evidence because nobody could tell what had actually been given.

There is a chemical reason this matters and it is not abstract. Analytical work quantifying the diterpenes responsible for the herb's dopaminergic activity found rotundifuran ranging from 0.04 to 0.30 percent across commercial samples of the dried drug — a sevenfold spread — and 1.04 to 2.23 percent across extracts. A named extract is a manufacturing process held constant and verified batch to batch. In the Ze 440 case, batches were checked specifically by their dopamine D2 receptor binding potential and found pharmacologically consistent. A generic capsule has no such guarantee.

None of this means an unnamed product cannot work. It means you have no way to know, and no trial to point at if it does not.

How to Read a Chasteberry Label

Two additional cautions specific to this herb. First, a marker is not a potency: agnuside and casticin are analytical fingerprints, easy to measure and useful for confirming you have the right plant, but the compounds carrying the dopaminergic activity are the lipophilic diterpenes, and no product on the market states a rotundifuran content. A stated agnuside percentage tells you the manufacturer tested the material; it does not predict effect.

Second, beware the blend. Chasteberry appears constantly inside multi-herb "hormone balance," "PMS support," "fertility" and "menopause" formulas, at doses hidden inside a proprietary blend. If you cannot see how much chasteberry you are taking, you cannot compare it to any trial — and you have also acquired every interaction and caution attached to whatever else is in the bottle.

Doses That Have Actually Been Tested

The most actionable finding in the whole chasteberry literature is the dose-ranging trial. One hundred and sixty-two women, four arms, three cycles: 8 mg did not beat placebo, 20 mg beat both placebo and 8 mg, and 30 mg added nothing over 20 mg. Under-dosing is a real failure mode. Over-dosing buys nothing.

There is a further reason not to guess low. A placebo-controlled study in twenty healthy men found chasteberry's effect on prolactin to be dose-dependent and bidirectional: the lowest of three doses significantly raised 24-hour and TRH-stimulated prolactin, while the highest lowered it. That is laboratory pharmacodynamics in men rather than a clinical outcome in women, so do not over-read it — but combined with the failed 8 mg arm, it argues that a very low dose is not a "gentle start," it is a different pharmacology.

Note also that the milligram figures above refer to native extract, not raw herb. A 400 mg capsule of milled dried berry is not "twenty times the trial dose" — it is a different preparation entirely, usually delivering less of the active fraction than a well-made 20 mg concentrated extract, and with no way to check.

Tinctures, Teas and Whole Berries

• Standardised tablets and capsules — the form with the evidence. Recommended default.
• Liquid extracts and tinctures — traditional in Anglo-American herbal practice, and one of the mastalgia trials used a chasteberry solution at 2 × 30 drops daily. But a "drop" is not a unit of dose: it depends on the extract ratio, the ethanol content, the dropper aperture and the viscosity. Unless a product states milligrams of native extract per millilitre, you cannot translate a trial dose into drops. Tinctures are also unsuitable for anyone avoiding alcohol.
• Whole or powdered dried berries — the least standardised option, with the sevenfold rotundifuran variability documented in trade samples applying at full force. Traditional dosing figures for crude fruit circulate in herbal texts, but no clinical trial supports them.
• Tea or infusion — poorly suited to this herb specifically. The diterpenes that carry the dopaminergic activity are lipophilic and were concentrated in the lipophilic fractions of extracts; hot water is a poor solvent for them. A chasteberry tea is a pleasant peppery drink with no reason to expect a trial-level effect.
• Multi-herb "hormone support" blends — avoid unless every ingredient and dose is disclosed. You cannot attribute benefit, you cannot attribute a side effect, and you inherit every caution in the formula.

How and When to Take It

1. Once daily, in the morning. Every major trial used once-daily dosing, and morning administration is conventional — prolactin secretion peaks overnight and falls through the morning, so the usual rationale is to have the herb present as that rhythm plays out. This is a sensible convention rather than a proven timing effect.
2. Every day of the cycle, not just premenstrually. Chasteberry shifts a hypothalamic–pituitary set-point; it is not a symptom pill. One Iranian trial did test six-days-before-menses dosing over six cycles with positive results, but it stands alone against a body of continuous-dosing evidence. Continuous is the evidenced approach.
3. With or without food. No trial establishes a food requirement. If it causes nausea, taking it with breakfast is reasonable.
4. Give it three full cycles. This is not marketing patience — it is the trial duration. The Japanese open-label study showed the symptom score falling significantly after cycle one and continuing to fall through cycles two and three, with the responder rate climbing throughout. Partial benefit early, most of it later.
5. Keep a symptom diary. Two cycles of baseline ratings before starting, then compare. Given a documented placebo response of around 50 percent in PMS trials, an impression is not evidence.
6. Stopping. No withdrawal syndrome or taper is described. In the Berger study, symptoms returned gradually across three post-treatment cycles but did not fully return to baseline — consistent with a set-point that drifts back rather than a drug wearing off.
7. If three cycles produce nothing, stop. Nothing in the literature suggests a longer run rescues a non-response, and roughly half of women in the BMJ trial did not meet the responder threshold.

Side Effects: What the Safety Review Found

The best single source is a systematic review of adverse events published in Drug Safety in 2005, which searched six databases, included WHO and national spontaneous-reporting data, and contacted twelve manufacturers and five herbalist organisations, with no language restrictions. It looked only at single-herb chasteberry products, excluding combinations and homeopathic preparations — which makes it unusually clean.

Its conclusion: adverse events following chasteberry are mild and reversible. The most frequent were:

• Nausea and other gastrointestinal disturbance
• Headache
• Menstrual disorders — spotting or shifts in cycle timing, most often early on
• Acne
• Pruritus (itching) and erythematous rash

The clinical trials line up with this. In the BMJ study, seven of 170 women reported mild adverse events — four on chasteberry, three on placebo — and none stopped treatment. In the 1,634-woman post-marketing observation, adverse drug reactions were suspected in 1.2 percent of patients with none serious. In the Japanese study, eight of 69 patients had non-serious adverse events, one of which was an allergic dermatitis whose relationship to the herb could not be ruled out. The mastalgia trials found no difference in adverse-event frequency between chasteberry and placebo.

Two honest qualifications. First, that safety review is from 2005; it remains the most systematic assessment available, but it is not recent. Second, "mild and reversible in trials" describes healthy volunteers taking a defined extract for three months under supervision — not necessarily an unstandardised product taken for years alongside other medicines.

Allergic reactions, while uncommon, do occur, and chasteberry is in the mint family (Lamiaceae) — historically classified in Verbenaceae — which is worth knowing if you have plant allergies.

Interactions: Dopamine Drugs

The 2005 systematic review states plainly that no drug interactions were reported in the literature it searched, and then, in the same breath, names the theoretical one: chasteberry might interfere with dopaminergic antagonists. Both halves of that sentence deserve weight. There is no documented case series of harm. There is also no interaction study, and absence of reports is not evidence of safety when nobody has looked.

The interaction logic is direct. Chasteberry binds the dopamine D2 receptor and mimics dopamine. Therefore:

Drugs that block dopamine — a potential opposition

• Antipsychotics — haloperidol, risperidone, paliperidone, amisulpride, olanzapine, quetiapine, aripiprazole and others. These work, in large part, by blocking D2. A weak D2 agonist pulls in the opposite direction. The theoretical concern is reduced therapeutic effect — and in schizophrenia or bipolar disorder, a partial loss of antipsychotic effect is a serious matter. Do not add chasteberry to an antipsychotic without your prescriber's involvement.
• Metoclopramide and domperidone — D2 antagonists used for nausea and gastric motility. Domperidone is also sometimes prescribed deliberately to raise prolactin and increase milk supply, which chasteberry would work directly against.
• Prochlorperazine and related antiemetics — same receptor class.

Drugs that boost dopamine — a potential addition

• Bromocriptine and cabergoline — the dopamine agonists used to treat prolactinoma and hyperprolactinaemia. Chasteberry acts in the same direction and has been studied as a comparator to bromocriptine for hyperprolactinaemia with mastalgia. Taking both simultaneously means an unmeasured additive effect on the very number your clinician is titrating against. If you are on one of these, chasteberry is a decision for your endocrinologist, not for you.
• Parkinson's disease dopamine agonists — ropinirole, pramipexole, rotigotine, and levodopa preparations. Same reasoning.

Related considerations

• Other prolactin-raising medications — some antidepressants, opioids and verapamil raise prolactin. If a prolactin-raising drug is causing symptoms, the right move is to review the drug with the prescriber, not to layer a herb on top.
• Monitoring interference. Anyone whose prolactin is being tracked — for a pituitary adenoma, for antipsychotic monitoring, in a fertility work-up — should tell whoever ordered the test that they are taking chasteberry. A partially suppressed prolactin can change a clinical decision.
• Hormone-sensitive conditions. Chasteberry binds oestrogen receptor beta weakly (via apigenin) and does not bind ERα, so a classical oestrogenic effect is unlikely. Still, if you have a history of a hormone-sensitive cancer or are on endocrine therapy such as tamoxifen or an aromatase inhibitor, clear any hormonally active herb with your oncology team before starting it.

Contraception, HRT and IVF

• Combined hormonal contraception. Honestly uncertain. The most relevant data point is incidental: in the Berger trial, 13 of 43 participants were taking oral contraceptives concurrently, and no difference in response was seen between women on and off the pill. That suggests chasteberry still worked in pill users; it says nothing about whether chasteberry affects contraceptive reliability, because nobody has studied it. Two practical rules: do not treat chasteberry as a contraceptive, and do not expect it to "regulate" a cycle that a contraceptive is already controlling — a pill bleed is a withdrawal bleed, not a natural luteal phase.
• Menopausal hormone therapy. No interaction data. The deeper point is that chasteberry has little rationale after menopause — its target is the luteal phase of an ovulating cycle, and there is no longer one. See Cycle Regulation and Fertility.
• IVF and assisted reproduction. Avoid unless your fertility specialist has explicitly approved it. Stimulated cycles are precisely choreographed with gonadotropins, agonists or antagonists and a timed trigger, and monitored with serial hormone measurements. Adding an unquantified agent that acts on pituitary dopamine receptors introduces an uncontrolled variable into a protocol built on control, and may complicate interpretation of monitoring bloods. Tell your clinic about any supplement before a cycle starts, not after.

Pregnancy and Breastfeeding

Pregnancy: avoid. A systematic review dedicated to chasteberry in pregnancy and lactation searched seven databases and graded what it found. In pregnancy the evidence is poor — theoretical, expert opinion and in-vitro only, with suggestions of oestrogenic and progesteronic activity, uterine stimulant activity, and emmenagogue activity. There are no adequate human safety data either way. The authors made a point that applies directly here: because chasteberry is commonly used by women of childbearing age, some will take it while unknowingly pregnant, and practitioners should keep that in mind when recommending it to anyone who might conceive.

The practical rule: if you are trying to conceive, either do not take chasteberry or stop as soon as a period is late. If you discover you were taking it early in pregnancy, this is a reason to mention it to your midwife or doctor, not a reason to panic — there is no established human teratogenicity signal, only an absence of data.

Breastfeeding: avoid. Here the mechanism gives an unusually clear answer. Prolactin drives milk production; chasteberry lowers prolactin; therefore chasteberry points against milk supply. Traditional European sources actually pointed both ways — some used it as a galactagogue — and the systematic review found expert opinion in outright conflict on whether chasteberry increases or decreases lactation. That conflict is itself a reason to stay away when milk supply matters. The 2005 adverse-event review reaches the same conclusion: use should be avoided during pregnancy or lactation.

Who Should Not Take It, and When to Stop

Do not start chasteberry if you:

• are pregnant, might be pregnant, or are breastfeeding
• take an antipsychotic, metoclopramide or domperidone
• take bromocriptine, cabergoline or a Parkinson's dopamine agonist
• are in or about to begin an IVF or other assisted-reproduction cycle, without your specialist's approval
• have a known raised prolactin that has not been investigated — see Prolactin and Hormonal Mechanism
• have a pituitary adenoma, diagnosed or suspected
• have a hormone-sensitive cancer or are on endocrine therapy, without oncology approval
• are under 18, where there are no trial data at all (the trials enrolled adults, typically 18–45)

Stop and seek advice if you develop:

• new, one-sided, focal or constant breast pain, a lump, skin dimpling, or nipple discharge — especially bloody or from a single duct. This is not cyclical mastalgia and it needs assessment
• milk-like discharge from the nipples when not breastfeeding (galactorrhoea) — a prolactin question that needs a work-up
• headaches with visual changes, particularly loss of peripheral vision — a red flag for a pituitary lesion
• a rash, itching or any allergic-type reaction
• markedly heavier bleeding, or bleeding between periods that persists beyond the first cycle or two
• any new symptom you would report to a doctor if a prescription drug had caused it

And tell your clinician you are taking it before any hormone testing, before fertility treatment, before surgery, and at every medication review. Herbal products are under-reported to clinicians as a matter of routine, and this one acts on a receptor several common drug classes also target.

Cost and Product Quality

Chasteberry is inexpensive relative to most supplements — typically in the range of a few pounds, euros or dollars per month, with named-extract products at the higher end and generic capsules at the lower. Given the price difference is usually small in absolute terms and the evidence attaches specifically to the named extracts, paying more for Ze 440 or BNO 1095 is one of the better-justified upgrades in the supplement aisle.

Practical points on quality:

• In the European Union, chasteberry products are frequently registered as traditional herbal medicinal products or, in Germany's case historically, as licensed medicines — which means a regulator has reviewed the manufacturing and labelling. The European Medicines Agency maintains a herbal monograph for Agni casti fructus.
• In the United States, chasteberry is sold as a dietary supplement. It is not reviewed for efficacy before sale, and content verification depends on the manufacturer. Look for third-party certification — USP, NSF, or an equivalent — and a certificate of analysis available on request.
• Buy the fruit, not the leaf. All the evidence is for the fruit.
• Check the expiry and store it dry and dark. The active diterpenes are not indefinitely stable, and there is no way for you to test them.
• Prefer a single-herb product over a blend, so that if something works or something goes wrong you know what caused it.

Key Research Papers

Every identifier below was verified live against NCBI E-utilities before being written; first author, title, journal and year all had to match.

Extract identity, standardisation and dose

1. Schellenberg R, Zimmermann C, Drewe J, Hoexter G, Zahner C. Dose-dependent efficacy of the Vitex agnus castus extract Ze 440 in patients suffering from premenstrual syndrome. Phytomedicine. 2012;19(14):1325–1331. The four-arm dose-ranging trial: 162 women; 8 mg failed, 20 mg worked, 30 mg added nothing.
2. Csupor D, Lantos T, Hegyi P, et al. Vitex agnus-castus in premenstrual syndrome: a meta-analysis of double-blind randomised controlled trials. Complementary Therapies in Medicine. 2019;47:102190. Only three of 21 trials described their preparation adequately — all three used Ze 440 or BNO 1095.
3. Hoberg E, Meier B, Sticher O. Quantitative high performance liquid chromatographic analysis of diterpenoids in agni-casti fructus. Planta Medica. 2000;66(4):352–355. Rotundifuran at 0.04–0.30 percent of the drug across trade samples — the quantitative case for buying a named extract.
4. Meier B, Berger D, Hoberg E, Sticher O, Schaffner W. Pharmacological activities of Vitex agnus-castus extracts in vitro. Phytomedicine. 2000;7(5):373–381. Ze 440 batches shown to be of constant pharmacological quality by D2 receptor binding — what standardisation actually buys.
5. Merz PG, Gorkow C, Schrödter A, et al. The effects of a special Agnus castus extract (BP1095E1) on prolactin secretion in healthy male subjects. Experimental and Clinical Endocrinology and Diabetes. 1996;104(6):447–453. Dose-dependent, bidirectional prolactin effects — the lowest dose raised prolactin, the highest lowered it.

Dosing regimens used in trials

1. Schellenberg R. Treatment for the premenstrual syndrome with agnus castus fruit extract: prospective, randomised, placebo controlled study. BMJ. 2001;322(7279):134–137. One tablet daily, three cycles.
2. He Z, Chen R, Zhou Y, et al. Treatment for premenstrual syndrome with Vitex agnus castus: a prospective, randomized, multi-center placebo controlled study in China. Maturitas. 2009;63(1):99–103. BNO 1095 corresponding to 40 mg herbal drug, three cycles.
3. Momoeda M, Sasaki H, Tagashira E, Ogishima M, Takano Y, Ochiai K. Efficacy and safety of Vitex agnus-castus extract for treatment of premenstrual syndrome in Japanese patients: a prospective, open-label study. Advances in Therapy. 2014;31(3):362–373. 20 mg once daily for three cycles; the clearest picture of how the response builds over time.
4. Ooi SL, Watts S, McClean R, Pak SC. Vitex agnus-castus for the treatment of cyclic mastalgia: a systematic review and meta-analysis. Journal of Women's Health. 2020;29(2):262–278. Typical dosing across 25 studies: 20–40 mg/day for three months.
5. Zamani M, Neghab N, Torabian S. Therapeutic effect of Vitex agnus castus in patients with premenstrual syndrome. Acta Medica Iranica. 2012;50(2):101–106. The one trial of intermittent (six days premenstrually) dosing.

Safety, adverse events and special populations

1. Daniele C, Thompson Coon J, Pittler MH, Ernst E. Vitex agnus castus: a systematic review of adverse events. Drug Safety. 2005;28(4):319–332. The definitive safety review: adverse events mild and reversible; most frequent were nausea, headache, gastrointestinal disturbance, menstrual disorders, acne, pruritus and rash; no drug interactions reported, but theoretical interference with dopaminergic antagonists; avoid in pregnancy and lactation.
2. Dugoua JJ, Seely D, Perri D, Koren G, Mills E. Safety and efficacy of chastetree (Vitex agnus-castus) during pregnancy and lactation. Canadian Journal of Clinical Pharmacology. 2008;15(1):e74–e79. Pregnancy evidence is theoretical and in-vitro only; expert opinion on lactation is in direct conflict.
3. Loch EG, Selle H, Boblitz N. Treatment of premenstrual syndrome with a phytopharmaceutical formulation containing Vitex agnus castus. Journal of Women's Health and Gender-Based Medicine. 2000;9(3):315–320. Worthless as efficacy evidence (no control group) but a genuine safety dataset: 1,634 women, suspected adverse drug reactions in 1.2 percent, none serious.
4. Berger D, Schaffner W, Schrader E, Meier B, Brattström A. Efficacy of Vitex agnus castus L. extract Ze 440 in patients with pre-menstrual syndrome (PMS). Archives of Gynecology and Obstetrics. 2000;264(3):150–153. The only oral-contraceptive observation in this literature: no difference in response between women on and off the pill; resting prolactin stayed physiological.
5. Roemheld-Hamm B. Chasteberry. American Family Physician. 2005;72(5):821–824. A concise primary-care overview of uses, dosing and cautions.
6. Izzo AA, Hoon-Kim S, Radhakrishnan R, Williamson EM. A critical approach to evaluating clinical efficacy, adverse events and drug interactions of herbal remedies. Phytotherapy Research. 2016;30(5):691–700. Useful framing for why "no reported interactions" is not the same as "no interactions."

Live PubMed Searches

1. Ze 440 extract
2. BNO 1095 extract
3. Chasteberry adverse events
4. Chasteberry drug interactions
5. Herb–drug interactions with dopamine antagonists
6. Agnuside standardisation by HPLC
7. Herbal supplement label accuracy
8. Herbal medicine safety in pregnancy

Connections

• All Herbs
• Chasteberry Benefits — the hub
• PMS and Cyclical Breast Pain — the trials these doses come from
• Prolactin and Hormonal Mechanism — why the interactions are what they are
• Cycle Regulation and Fertility
• Chasteberry (Vitex)
• Reproductive Medicine
• Black Cohosh
• Dong Quai
• White Peony Root (Bai Shao)

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