Kampo herbs intertwine with the CYP3A4 enzyme, symbolizing the intersection of traditional and modern medicine.

Kampo's Interaction with Modern Medicine: What Women Need to Know About CYP3A4 and Drug Safety

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Kai Mendoza in Health & Wellness July 2025 • 4 min read.

"Unveiling the Synergies and Risks of Traditional Japanese Remedies in Gynecological Health"


As integrative medicine gains popularity, combining modern Western practices with traditional remedies, understanding potential interactions becomes crucial. This is especially important in Japan, where Kampo medicines are increasingly used. One well-known interaction involves grapefruit juice (GFJ) and its effect on certain drugs due to its inhibition of the CYP3A4 enzyme found in the small intestine.

CYP3A4 inhibition can alter drug concentrations in the body, impacting their effectiveness and safety. While some Kampo medicines containing furanocoumarins have shown CYP3A4 inhibition in lab settings, their impact in real-world scenarios remains a key question. High dosages of Kampo medicines have, in some studies, shown CYP3A4 inhibition or induction in animals, but clinical effects are often minimal. This raises the need for careful evaluation of drug interactions with Kampo.

To better inform healthcare providers and patients, comparing the inhibitory effects of Kampo medicines with GFJ on CYP3A4 is essential. Since GFJ is a recognized CYP3A4 inhibitor in clinical studies, it serves as a useful benchmark. This article examines the CYP3A4 inhibitory potential of Kampo formulas commonly prescribed in gynecology and compares their effects to GFJ, aiming to provide insights into the safe use of these traditional medicines.

The Study: Kampo Formulas and CYP3A4 Inhibition

Kampo herbs intertwine with the CYP3A4 enzyme, symbolizing the intersection of traditional and modern medicine.

A recent study investigated the interaction between traditional Japanese Kampo formulas and modern medicine, focusing on the CYP3A4 enzyme. This enzyme is crucial for metabolizing many drugs, and its inhibition can lead to increased drug concentrations, potentially causing adverse effects. The research specifically examined three Kampo formulas frequently prescribed in gynecological clinics: Tokishakuyakusan, Kamishoyosan, and Keishibukuryogan.

Researchers evaluated the inhibitory effects of these Kampo formulas on CYP3A4 in vitro, comparing them to grapefruit juice (GFJ), a known CYP3A4 inhibitor. They prepared extracts from crude drugs and assessed their impact on CYP3A4 activity. The goal was to determine the extent to which these Kampo medicines could potentially interfere with drug metabolism in clinical settings.

The key findings from the study highlight the nuances of Kampo-drug interactions:
  • All three Kampo formulas exhibited some level of CYP3A4 inhibition in the laboratory.
  • The potential for Tokishakuyakusan and Keishibukuryogan to cause significant drug interactions appears to be low.
  • Excessive dosages of Kamishoyosan may pose a risk of drug interaction with CYP3A4 substrates.
These results suggest that while Kampo medicines can interact with CYP3A4, the clinical significance varies. Kamishoyosan, in particular, warrants attention regarding dosage, while the other two formulas seem less likely to cause interactions. This information is vital for women using Kampo medicines in conjunction with other medications.

Implications for Women's Health

Understanding the interaction between Kampo medicines and CYP3A4 is crucial for women's health, particularly for those using these remedies alongside conventional drugs. While the study suggests that Tokishakuyakusan and Keishibukuryogan pose a low risk of drug interaction, caution is advised with Kamishoyosan, especially at higher dosages. Further clinical studies are needed to fully elucidate the potential risks and ensure the safe and effective use of Kampo medicines in conjunction with other medications. Always consult with healthcare provider.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1155/2018/4259603, Alternate LINK

Title: Inhibitory Effect Of Japanese Traditional Kampo Formula Frequently Prescribed In Gynecological Clinics On Cyp3A4

Subject: Complementary and alternative medicine

Journal: Evidence-Based Complementary and Alternative Medicine

Publisher: Hindawi Limited

Authors: Hao Ni, Takashi Matsumoto, Junko Watanabe, Toshiaki Makino

Published: 2018-10-01

Everything You Need To Know

1

What exactly is Kampo, and why should women be aware of its potential interactions with other medications?

Kampo is a traditional Japanese medicine. When used alongside conventional drugs, it's important to understand how they might interact. Some Kampo medicines can affect how the body processes other drugs, particularly through an enzyme called CYP3A4.

2

What is CYP3A4, and how does it relate to potential drug interactions when using Kampo?

CYP3A4 is an enzyme in the body that helps metabolize many drugs. If something inhibits CYP3A4, it can lead to increased drug concentrations, potentially causing adverse effects. Certain substances, like grapefruit juice (GFJ), are known to inhibit CYP3A4.

3

Which specific Kampo formulas were studied, and what was the primary method used to evaluate their interaction with CYP3A4?

The research specifically examined three Kampo formulas frequently prescribed in gynecological clinics: Tokishakuyakusan, Kamishoyosan, and Keishibukuryogan. Researchers evaluated the inhibitory effects of these Kampo formulas on CYP3A4 in vitro, comparing them to grapefruit juice (GFJ), a known CYP3A4 inhibitor. While all three Kampo formulas exhibited some level of CYP3A4 inhibition in the laboratory, the clinical significance varies.

4

What are the key takeaways regarding the use of Tokishakuyakusan, Kamishoyosan, and Keishibukuryogan in relation to CYP3A4 inhibition?

The study indicated that Tokishakuyakusan and Keishibukuryogan pose a low risk of drug interaction via CYP3A4. However, excessive dosages of Kamishoyosan may pose a risk of drug interaction with CYP3A4 substrates. It is important to note that these results are from in vitro studies and clinical significance can vary.

5

Considering that some Kampo medicines can inhibit CYP3A4 in lab settings, what are the broader implications for patient safety, and what further research is needed?

While some Kampo medicines showed CYP3A4 inhibition in lab settings, their impact in real-world scenarios requires careful evaluation. High dosages of Kampo medicines have, in some studies, shown CYP3A4 inhibition or induction in animals, but clinical effects are often minimal. Further clinical studies are needed to fully elucidate the potential risks and ensure the safe and effective use of Kampo medicines in conjunction with other medications. Always consult with a healthcare provider.

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