Drug interactions with phytotherapeutics in oncology

Area of Science:

• Pharmacology
• Oncology
• Herbal Medicine Interactions

Background:

• Complementary and alternative medicine use is prevalent among cancer patients (30-70%).
• Herb-drug combinations are common, posing risks for anti-neoplastic and palliative treatments.

Purpose of the Study:

• To review pharmacokinetic drug interactions involving common herbal products used by cancer patients.
• To highlight potential risks and safe co-administration guidelines.

Main Methods:

• Literature review of pharmacokinetic interactions.
• Focus on frequently used herbs: garlic, ginkgo, ginseng, echinacea, and St. John's wort (SJW).

Main Results:

• Garlic and ginkgo show no significant adverse interactions.
• Ginseng requires monitoring for CYP2C9 substrates (e.g., warfarin).
• Echinacea may induce CYP3A metabolism, relevant for narrow therapeutic index drugs.
• St. John's wort (SJW) significantly affects CYP3A4, CYP2C9, and P-glycoprotein, reducing drug exposure by up to 70%.

Conclusions:

• Herb-drug interactions are complex and often under-researched.
• SJW poses the most significant risk, potentially impacting tyrosine kinase inhibitors.
• Close monitoring is crucial for certain herb-drug combinations, especially with SJW.