Kampo Safety: Liver Injury, Interstitial Pneumonia and Interactions

Kampo is Japan's form of traditional herbal medicine, and in Japan its formulas are usually prescribed by physicians as standardized extract products. [1] Being traditional, or prescribed by a doctor, does not make a product free of risk. Japanese clinicians have documented several kinds of harm, and this page summarizes them in plain language. It is information only and not a reason to stop any medicine you are taking. If you take a Kampo product and are worried, talk to the prescriber or a pharmacist.

If someone has trouble breathing, collapses or cannot be woken, call 911 in the United States. For poisonings in the US, Poison Help is 1-800-222-1222. See poison help by country.

The main types of harm reported

A Japanese review of Kampo adverse effects groups them by likely cause. [2]

The review's authors say these potential adverse effects should be considered when prescribing Kampo. [2]

Liver injury

A systematic review of case reports of Kampo-related liver injury analyzed 37 cases and found that 65.9% were associated with Scutellaria root, with onset typically within about 45 days (range 1 to 730). [3] The authors point out that because re-testing a drug after liver injury is unethical, the review relied mostly on case reports, so it cannot show how common this is. They recommend close liver monitoring in the first two months, particularly for formulas with Scutellaria root. [3]

A genetic study of 287 Japanese patients with drug-induced liver injury found that a particular immune-gene type, HLA-B*35:01, was present in 12 of 19 Kampo-related cases, versus 15.2% of healthy volunteers. [4] The authors call it a potential predictive marker in the Japanese population. [4] That is a research finding and not a routine screening test, and we did not find it studied in other populations in the sources we read.

For general liver safety with herbs and supplements, see liver safety and supplements.

Lung inflammation (interstitial pneumonia and pneumonitis)

A review of 73 reported cases of pneumonitis from Japanese herbal medicine found:

• Shosaikoto was the product most often named (26%), followed by sairei-to (16%); these commonly contain Scutellaria root and licorice. [5]
• 89% of cases developed within 3 months of starting. [5]
• 36% recovered just by stopping the herbal medicine, while others needed immune-suppressing treatment, 13 patients (18%) needed mechanical ventilation and three (4%) died. [5]

The authors conclude most events are not severe, but critical cases should be recognized. [5]

A larger analysis of 830,079 reports in the Japanese Adverse Drug Event Report database found signals for 32 of 54 herbal medicines, and a dose-related pattern for Scutellaria root, with a higher reporting association in people aged 60 and over. [6] The authors advise early detection and avoiding inadvertent administration. [6]

These numbers come from voluntary case reports and a literature review. They cannot give the true risk for a given person, because we do not know how many people took the products without a problem. Both sources show that the risk is real and that early recognition matters.

Licorice, low potassium and blood pressure

Licorice (kanzo) is in many Kampo formulas. Too much can cause pseudoaldosteronism: high blood pressure, low potassium and muscle weakness, which can be fatal. [7][2] In yokukansan data, older age, dementia, low body weight and a higher licorice dose were linked to more cases, and loop diuretics tended to raise risk, though not significantly. [7] A hospital study found 8.3% of 665 mostly older patients on yokukansan developed low potassium, and advised monitoring. [8] See yokukansan in dementia care and licorice root tea.

Interactions and combinations

We did not find a systematic list of Kampo and medicine interactions in the sources we read, so we do not make one up. What the sources do show:

• Several formulas share the same ingredients, such as licorice and Scutellaria root. [5] Taking more than one product, or a Kampo product with a licorice tea or supplement, can add up. See amounts and duplicate ingredients.
• Loop diuretics tended to be associated with pseudoaldosteronism in one analysis. [7]
• A Japanese database analysis found a higher association with lung inflammation when Scutellaria root and Pinelliae tuber were taken together. [6]

Ask a pharmacist to check every product against your medicines. For the wider picture, see how interactions work.

Pregnancy and children

We did not find sourced guidance on specific Kampo formulas in pregnancy or breastfeeding, so we do not give any. The pneumonitis review included patients as young as 7. [5] Ask a clinician before using any herbal product in pregnancy or for a child, and see pregnancy and breastfeeding.

Questions to ask

• What is in this product, and does it contain licorice or Scutellaria root?
• Which tests, such as potassium or liver tests, make sense, and when?
• What symptoms mean I should stop and call?

For how Kampo is regulated in Japan, see Kampo in the Japanese health system.