The Study
Synergy, Additive Effects, and Antagonism of Drugs with Plant Bioactive Compounds
This study is like a big report that collects stories from other experiments about how plant stuff (like turmeric or green tea) might change how medicines work. But most of those stories weren’t from real people taking medicine—they were from test tubes or animals. So we can say 'maybe' or 'it looks like,' but we can’t say 'this definitely happens in humans.'
Analysis score
Maximum 85 for a systematic review.
Where the score came from
Some plants like black pepper, green tea, and St. John’s wort can make your medicines work better, worse, or even stop them from working at all by changing how your body absorbs or breaks them down.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 534 / 100
Quality score
Systematic reviews and meta-analyses of cohort studies. They sit above a single cohort study but below a single randomized trial, because the underlying evidence is still observational.
Key takeaways
Summary
Based on the study abstract and findings.
- 1Yes—these changes can mean your medicine doesn’t work (risking transplant rejection or birth control failure) or becomes too strong (risking overdose or toxicity).
- 2Piperine (in black pepper) can make curcumin 20x more available in the body; St.
- 3John’s wort can cut cyclosporine levels by up to 50%; grapefruit juice can block fexofenadine absorption by 70%.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Drugs and Drug Candidates
Year
2025
Authors
N. Chaachouay
Related Content
Claims (7)
Plants produce chemical compounds for defense that human metabolic systems are not fully adapted to process, resulting in disruption of normal physiological processes.
Curcumin reduces the ability of chemotherapy drugs like doxorubicin to kill cancer cells by removing reactive oxygen species that these drugs need to work.
Certain plant-derived chemicals change how drugs are absorbed, distributed, metabolized, and acted upon in the body, which can either increase or decrease the drug's effectiveness depending on the specific chemical and drug combination.
Piperine increases the amount of curcumin that enters the bloodstream by slowing down its breakdown in the liver and intestines, which allows effective doses of curcumin to be reduced.
St. John’s wort increases the activity of liver enzymes that break down certain drugs, causing lower levels of those drugs in the blood and reducing their effectiveness.
Grapefruit juice blocks specific transporters and enzymes in the intestine that process certain drugs, causing higher levels of those drugs in the bloodstream and altering their effects.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.