Prefemin: The Once-a-Day PMS Tablet at Japanese Drugstores
Japan has one OTC medicine made for PMS. Prefemin is a once-a-day chasteberry tablet you can buy at a drugstore. Here's who it's for, how to take it, and who shouldn't.
If PMS hits a few days before your period, with tight breasts, a headache, and a short fuse, Japan has an OTC medicine for it. Prefemin (プレフェミン) by Zeria Pharmaceutical is a PMS medicine containing chasteberry dry extract 40 mg per tablet, a Western herb. The maker describes it as the only OTC medicine for PMS in Japan.
It's a Class 2 medicine (第2類医薬品), so you can buy it at an ordinary drugstore or online. No prescription needed. This page explains how to use it, from the Japanese package insert and the maker's website.
Quick summary
- Approved for these PMS symptoms: breast tension, headache, irritability, getting angry easily, and mood swings.
- For women 18 and older: 1 tablet, once a day, every day.
- Don't take it while breastfeeding. It is not a medicine for pregnant women.
- No better after about 1 month? Stop and talk to a doctor or pharmacist.
What Prefemin Treats
The package insert describes PMS (premenstrual syndrome, 月経前症候群) as physical or emotional discomfort that starts before your period and goes away once your period begins. It appears in the luteal phase, the days between ovulation and your period, and sharp changes in female hormones such as progesterone and estrogen are thought to be one cause.
Chasteberry (チェストベリー) is the fruit of the chaste tree, whose botanical name is Vitex agnus-castus. The package insert also calls it chaste tree (チェストツリー) or agni (アグニ).
Prefemin is approved to relieve these five premenstrual symptoms:
- Breast tension (乳房のはり)
- Headache (頭痛)
- Irritability (イライラ)
- Getting angry easily (怒りっぽい)
- Mood swings (気分変調)
How to Take Prefemin
- Women 18 and older: 1 tablet, once a day. Under 18: do not take.
- Take it every day, not only when symptoms appear. To avoid missed doses, pick a time that suits you and take it at the same time each day.
- If you start right after your period begins, the package insert says you are likely to notice improvement in about 1 month. The maker's FAQ recommends starting on the first day of your period.
- Forgot a dose? Don't take 2 tablets the next day. Just take your usual 1 tablet (maker's FAQ).
- Press the tablet out of the PTP sheet before taking it. Swallowing the sheet can injure your esophagus.
Who Shouldn't Take Prefemin
The package insert says not to take it if you:
- Are breastfeeding.
- Have ever had an allergic reaction to Prefemin or to chasteberry (also called chaste tree or agni).
While taking Prefemin, don't eat or drink foods that contain chasteberry (chaste tree, agni).
Prefemin is not a medicine for people who are pregnant or might be pregnant, and its safety during pregnancy has not been established.
Talk to a doctor, pharmacist, or registered salesperson first if you:
- Are under medical treatment.
- Have ever had an allergic reaction to a medicine.
- Take kampo (traditional Japanese herbal) medicine.
- Have been diagnosed with depression.
- Have breast tension or lumps that don't follow your menstrual cycle.
- Have irregular periods.
Side Effects and When to Stop
Stop taking it right away and talk to a doctor, pharmacist, or registered salesperson, bringing the package insert, if you get:
- Skin: rash, redness, or itching
- Digestive: nausea or diarrhea
- Other: menstrual changes, such as a change in your cycle or in how heavy your period is
- In rare cases, PMS symptoms can feel stronger when you first start taking it.
- If your symptoms are no better after about 1 month, stop taking it and talk to a doctor, pharmacist, or registered salesperson, bringing the package insert.
- Even if it helps, talk to a doctor regularly if you keep taking it for more than 3 months.
What the Maker's Study Showed
Zeria's website shows data from the study submitted for approval. Women with PMS took 1 tablet a day for 3 menstrual cycles, and rated their symptoms on a 10 cm scale before and during treatment. Scores for breast tension, headache, irritability, anger, and depressed mood went down over the 3 cycles.
Keep in mind that this was an open-label study (67 women for effectiveness, 69 for safety) with no placebo or comparison group. One case of allergic dermatitis was reported as a side effect.
Not Just Medicine: Daily Habits
The package insert says improving daily habits can also be expected to ease PMS symptoms, and recommends it alongside medicine. Zeria's website suggests a regular routine, a balanced diet, less alcohol, salt, and caffeine, light aerobic exercise, and not smoking.
Where to Buy Prefemin in Japan
The Prefemin box: 30 tablets (30 days). Look for プレフェミン and 第2類医薬品.
- Where: drugstores and pharmacies. As a Class 2 medicine, a pharmacist or registered salesperson (登録販売者) can sell it. Learn more about Japan's medicine classes.
- Online: Class 2 medicines can be bought online, including on Amazon Japan.
- Pack size: the box shown is 30 tablets, a 30-day supply.
If your Japanese is limited
「プレフェミンはありますか？」
Purefemin wa arimasu ka?
"Do you have Prefemin?" Read it out, or just show this Japanese text on your phone.
Sources & Documents
- Package insert (Japanese PDF)
- Prefemin brand site (Japanese): product information, study data, and FAQ
- European Medicines Agency: Agni casti fructus: the botanical name of chasteberry, Vitex agnus-castus L.
This page summarizes the Japanese package insert for Prefemin and the maker's website and FAQ (October 2026). OTC Guide Japan translated and explained it in English. It is for information only and doesn't replace advice from a doctor or pharmacist. Always read the package insert that comes with the medicine.