What is Shakanzoto?

Shakanzoto is a herbal formula from Kampo. Kampo is the Japanese form of old Chinese herbal medicine. People take it when the heart feels like it pounds, flutters or skips.

It is used most often when that beat comes with low energy, a dry mouth and dry skin. Some Japanese doctors also give it for a weak pulse or a dry cough. Shakanzoto is the romanised Japanese name of the formula.

It sits on the list of 148 Kampo formulas that Japan's health ministry (MHLW) covers under national health insurance. That means a doctor there can prescribe it.

Here is the short verdict. Its place in the old texts is strong, but good human trials are missing. Long use in a tradition is not proof that a remedy works, and that holds true here.

How does Shakanzoto work?

No one has shown how this formula works. In Kampo thinking, it feeds body fluids and blood, and steadies the beat. That is an idea from tradition, not a lab finding.

Lab work does explain one herb well. Licorice makes the body hold on to salt and water. That can raise blood pressure and drop potassium, a body salt your heart needs.

Low potassium can itself upset the heart beat. So the same herb may help one person and unsettle the next. This is why a doctor should watch you while you take it.

What forms does Shakanzoto come in?

Most people in Japan take it as dried extract granules in single-dose sachets. Tsumura's product code TJ-64 is the best known one.

You may also find it as a powder, as small tablets, or as raw herbs you simmer into a tea. Strength varies a lot between products, so follow the label on the pack you hold.

Where it comes from:

The recipe first appears in the Shanghan Lun, a Chinese text linked to Zhang Zhongjing from about 200 CE. Its other old name means "restore the pulse" (fukumyakuto in Japanese).

It travelled to Japan and became a set formula in Kampo practice. It is still in daily use there today for a racing or uneven pulse.

What does Shakanzoto help with?

• Palpitations (a pounding or fluttering heartbeat): This is the classic reason Kampo doctors reach for it. The old texts describe exactly this picture, and Japanese practice has kept it for centuries. We could not find a solid human trial that tests whether it beats a dummy pill.
• Extra or skipped heartbeats, alongside normal medical care: Japanese case reports describe its use next to standard heart drugs. These reports cannot show cause and effect. Never use it in place of care for an uneven heartbeat, because an untreated rhythm problem can be dangerous.
• Tiredness with a weak or thready pulse: In Kampo this pattern is the main target of the formula. Support here is traditional rather than trial-based. Lasting tiredness has many causes, some serious, so get it checked first.
• Dry mouth and dry skin: Rehmannia and ophiopogon are the moistening herbs in the mix, and tradition uses them for this. No human trial has tested the whole formula for dryness. A very dry mouth can signal diabetes or a gland problem, so ask a doctor.
• Dry cough with little phlegm: A secondary use in Japanese practice, drawn from the same moistening herbs. Evidence is traditional only. A cough lasting more than three weeks needs a doctor, not a herb.

Which foods are rich in Shakanzoto?

1. Real licorice sweets and licorice tea: same plant, so they add to the blood pressure and potassium risk
2. Fresh ginger: one of the herbs in the formula, though food amounts are small
3. Jujube dates: another of the herbs, eaten as a dried fruit in East Asia

Practical Tips:

Cut out licorice sweets and licorice tea while you take this formula.

What are the side effects of Shakanzoto?

• Raised blood pressure
• Swelling of the ankles, hands or face from held fluid
• Low potassium (a drop in an important body salt)
• Muscle weakness, cramps or aching, which can mean muscle damage
• Quick weight gain from fluid, not fat
• Headache
• Nausea or stomach upset
• Loose stools, since hemp seed acts as a mild laxative
• Skin rash or itching
• Rare liver problems, seen with a number of Kampo formulas

Good to know:

Most people who take a short course have no trouble. The problems that matter come from licorice and grow with dose and time.

Together, raised blood pressure, held fluid, low potassium and muscle weakness are called pseudoaldosteronism (a salt-and-water imbalance caused by licorice). It is well described in Japan and can happen at normal doses.

Older people, women and anyone on water tablets are at higher risk. Stop and call a doctor if these signs start.

How much Shakanzoto should you take?

• Recommended daily: There is no dose set by research. Japanese extract granule products for adults are usually 7.5 g a day, split into two or three doses. Strength differs between brands and between granules and raw herbs. Follow your pack or your prescriber, and never double up on your own. Do not take another licorice-containing Kampo formula at the same time unless a doctor has checked the total licorice for you.
• Best time of day: Doses are usually spread through the day, often in the morning, at midday and in the evening.
• With or without food: Japanese practice is to take it before meals or between meals, with warm water. If it upsets your stomach, taking it with a little food is reasonable.
• Time to effect: Kampo practice expects some change within one to two weeks. If nothing has shifted after four weeks, stop and go back to your doctor.
• How long to take it: Treat it as a short course, not a daily habit. Two to four weeks is a normal point to stop and review with a doctor. The longer you take licorice, the higher the risk of raised blood pressure and low potassium. If you keep going for months, your doctor should check your blood pressure and your blood potassium.