Green tea commonly reduces systemic exposure of many oral drugs—mainly via intestinal transporter inhibition, P-gp modulation, or reduced solubility—potentially impacting efficacy and safety.

Background

Green tea catechins (notably EGCG) can affect drug solubility, transporters (OATP, P-gp, BCRP), and metabolizing enzymes, prompting concern for food–drug interactions.

Patients

Seventeen clinical studies (15 drugs) mostly in healthy adults; two patient cohorts: breast cancer (n=14; tamoxifen) and pulmonary fibrosis (n=26; nintedanib).

Intervention

Concomitant green tea/catechin intake (brewed tea, commercial beverages, or extracts; ~50–860 mg catechins; EGCG up to ~800 mg), sometimes with 4–14 days pretreatment.

Control

Drug administered with water/no green tea.

Outcome

Primary pharmacokinetics (AUC); secondary: Cmax, Tmax, urinary excretion, clearance; mechanistic inferences; case reports of clinical effects.

Study Design and Level of Evidence

Systematic review of clinical pharmacokinetic crossover studies (mostly randomized/open-label); 2011 OCEBM Level 2a.

Follow up period

Single-dose PK sampling typically 8–96 hours; pretreatment 4–14 days; one 6-day BID extract regimen.

Results

• Primary outcome (AUC): 72% of analyses showed decreased exposure (18–99%) for atorvastatin, celiprolol, digoxin, fexofenadine, folic acid, lisinopril, nadolol, nintedanib, raloxifene, rosuvastatin; 6% increased exposure (sildenafil +50%); 22% no change (fluvastatin, pseudoephedrine, simvastatin, tamoxifen).
• Secondary outcomes: Mechanisms predominantly intestinal OATP inhibition (esp. OATP1A2/2B1), P-gp modulation, and reduced solubility for poorly soluble drugs (e.g., raloxifene); CYP/UGT inhibition minimal in vivo.
• Timing/pretreatment: Effects persisted when tea taken ~1 hour before dosing; little difference between acute vs. short-term pretreatment.
• Genetics: Limited/modest modulation (e.g., ABCB1, ABCG2) without consistent impact on interaction magnitude.
• Clinical signals: Case reports link interactions to loss of efficacy (nadolol, sunitinib) or toxicity (erlotinib, tacrolimus).

Limitations

• Heterogeneous tea formulations, doses, and schedules; variable catechin content.
• Small samples in some studies; mostly healthy volunteers.
• Systemic catechin concentrations often unmeasured; elimination effects underexplored.
• Case reports are anecdotal and uncontrolled.

Funding

Industry

Citation

Kyriacou NM, Gross AS, McLachlan AJ. Green Tea Catechins as Perpetrators of Drug Pharmacokinetic Interactions. Clinical Pharmacology & Therapeutics. 2025;118(1):45-61. doi:10.1002/cpt.3547.