Educational information, not medical advice — ask your doctor or midwife.
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.
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.
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.
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.
Stop taking it and see a doctor the same day if your muscles feel weak or crampy, if your ankles, hands or face swell, or if you gain weight quickly without eating more. These can be the first signs of low potassium.
Get urgent help if your heartbeat gets faster, more uneven or harder to ignore, or if you feel faint, short of breath or have chest pain.
Also see a doctor if your urine turns dark brown, if your skin or the whites of your eyes turn yellow, or if a rash spreads. And book a check if palpitations or tiredness have not settled after four weeks.
Evidence grades and traditional-use labels are explained in our methodology. Nothing here is medical advice.
Reviewed by the HealisticMD editorial team How we grade evidence →
The published evidence for Shakanzoto is weak or absent. That usually means no controlled trial has tested it, not that a trial found it ineffective — the two are different, and we grade only what has been published.
What it is typically used for, usual dose, cautions, and the study behind it where real trial data exists.
One email with the summary. We'll also send a short weekly evidence update — unsubscribe any time.
