What is the evidence for using chasteberry (Vitex agnus‑castus) to treat moderate‑to‑severe premenstrual syndrome in reproductive‑age women, including recommended dose and safety precautions?

Evidence for Chasteberry (Vitex agnus-castus) in Premenstrual Syndrome

Chasteberry extract Ze 440 at 20 mg daily is an effective treatment for moderate-to-severe premenstrual syndrome, demonstrating superior efficacy to placebo with a responder rate of 52% versus 24% for placebo, and should be taken for at least three menstrual cycles. 1

Efficacy Evidence

The strongest evidence supports chasteberry for PMS relief based on multiple high-quality randomized controlled trials:

• A 2019 meta-analysis of three double-blind, placebo-controlled trials (520 women) using properly characterized extracts (Ze 440 and BNO 1095) found women taking chasteberry were 2.57 times more likely (95% CI 1.52-4.35) to experience symptom remission compared to placebo 2

• A 2017 systematic review and meta-analysis of 14 randomized controlled trials showed a large pooled effect (Hedges g, -1.21; 95% CI -1.53 to -0.88), though heterogeneity was high and publication bias was present 3

• The landmark BMJ trial of 170 women demonstrated significant improvement (P<0.001) in irritability, mood alteration, anger, headache, and breast fullness compared to placebo, with 52% responder rate versus 24% for placebo 1

Recommended Dosing

The optimal dose is 20 mg daily of the standardized extract Ze 440:

• A dose-finding study of 162 women compared 8 mg, 20 mg, and 30 mg doses over three menstrual cycles 4

• The 20 mg dose showed significantly greater improvement in total symptom score compared to both placebo and the 8 mg dose 4

• The 30 mg dose provided no additional benefit over 20 mg, establishing 20 mg as the preferred daily dose 4

• Treatment should continue for at least three consecutive menstrual cycles to achieve full therapeutic effect 1

Symptom Coverage

Chasteberry effectively treats both physical and psychological PMS symptoms:

• Physical symptoms: breast fullness, bloating, headache 1

• Psychological symptoms: irritability, mood alteration, anger 1

• A 2013 systematic review confirmed efficacy for premenstrual syndrome, premenstrual dysphoric disorder, and latent hyperprolactinemia 5

Safety Profile

Chasteberry demonstrates excellent tolerability with minimal adverse events:

• Adverse events are mild and generally infrequent across all trials 5

• In the BMJ trial, only 7 of 170 women (4%) reported mild adverse events, with none requiring treatment discontinuation 1

• The 20 mg dose was well tolerated with no significant safety concerns 4

Important Clinical Caveats

Key limitations and considerations for clinical practice:

• Only use properly characterized, standardized extracts (Ze 440 or BNO 1095) as the majority of chasteberry studies cannot be used as evidence due to incomplete product characterization 2

• The 2017 meta-analysis noted high risk of bias in most trials, high heterogeneity, and publication bias, suggesting the pooled effect may overestimate true treatment benefit 3

• Comparative efficacy versus conventional treatments (SSRIs, oral contraceptives) remains unclear, as head-to-head trials are limited 3

• One small trial suggested equivalence to fluoxetine for premenstrual dysphoric disorder, though another found fluoxetine superior 5

Practical Implementation

For women with moderate-to-severe PMS seeking treatment:

• Prescribe chasteberry extract Ze 440 20 mg once daily 4

• Initiate treatment and continue for minimum of three consecutive menstrual cycles before assessing response 1

• Assess symptom improvement using validated scales for irritability, mood changes, breast fullness, bloating, and headache 1

• Consider a responder as achieving ≥50% reduction in symptom severity 1

• If inadequate response after three cycles or if symptoms are severe, consider conventional therapies (SSRIs, oral contraceptives) as alternatives 3