The short answer
Green tea extract can contribute caffeine, which may increase clozapine levels. Check the actual caffeine content with your pharmacist before starting, stopping or changing the product. A large extract dose does not necessarily mean a large caffeine dose.
What this answer covers
Oral Camellia Sinensis Leaf Extract that contains caffeine. Catechin or extract mass alone does not establish caffeine exposure. Coffea arabica seed extract is a separate botanical and is not assessed in this pair.
- Supplement or preparation
- Camellia Sinensis Leaf Extract
- Medication ingredient
- clozapine
Which product matters
A USDA and NIH study tested 32 green tea products and found substantial variation in caffeine content. Some low-caffeine or decaffeinated products still had measurable caffeine. The weight of extract on the label cannot reliably tell you how much caffeine it supplies.
Why caffeine matters with clozapine
Caffeine can slow the breakdown of clozapine. A small healthy-volunteer study found increased clozapine exposure, and a small patient study found higher concentrations during caffeinated coffee use. Neither study tested this botanical. These results justify checking caffeine exposure without predicting the same effect for everyone.
Plan changes with your care team
Give your pharmacist the full product label, serving size and frequency, together with your coffee, tea, energy drinks and other supplements. Keep intake reasonably consistent until your prescriber advises how to change it. The prescriber may monitor symptoms or clozapine levels and adjust treatment if needed. Do not change the clozapine dose yourself.
Dose changes and symptoms
Taking this supplement a few hours apart from clozapine has not been shown to prevent the caffeine interaction. Any clozapine dose adjustment should be based on your prescriber's assessment, not a general rule for another medicine. Contact your care team promptly if a product change is followed by new or worsening side effects.
Evidence and practical considerations
Absorption & effectiveness
When this oral botanical preparation supplies caffeine, it may inhibit clozapine metabolism and increase clozapine exposure. The magnitude depends on actual caffeine intake and individual response.
- Exact scope
- Oral Camellia Sinensis Leaf Extract that contains caffeine. Catechin or extract mass alone does not establish caffeine exposure. Coffea arabica seed extract is a separate botanical and is not assessed in this pair. with clozapine, RxCUI 2626 IN, oral treatment.
- Medication form and route
- Oral clozapine with oral caffeine-containing botanical preparation
What remains uncertain
- Evidence is indirect for this botanical. The studies used caffeine or coffee, not this exact preparation. The effect size, safe caffeine threshold and frequency of clinical toxicity cannot be predicted for an individual product. This does not establish increased absorption, a fixed dose reduction or an effective hour-based separation rule.
Factors that may matter: Actual caffeine per serving; Total caffeine from all sources; Starting, stopping or changing intake; Individual response.
Read the supporting source summaries
Source 1: current product label
dailymed.nlm.nih.gov · Source check Sep 10, 2026
Population: People prescribed clozapine.
Advises monitoring for adverse reactions and considering a clinician-directed clozapine reduction if needed. The one-third dose rule is specified for strong CYP1A2 inhibitors, not caffeine.
How this applies: Exact clozapine guidance for caffeine. Applied to this botanical only when the oral preparation supplies caffeine; the label does not name this botanical.
Label does not provide a fixed caffeine dose, a universal coffee amount, or an hour-based separation instruction.
Source 2: randomized crossover pharmacokinetic study
ebi.ac.uk · Source check Sep 10, 2026
Population: 12 healthy nonsmoking men.
Clozapine AUC rose 19% and clearance fell 14%; both reported P=.05.
How this applies: Direct caffeine-clozapine evidence, indirect for this botanical. Supports a constituent-based metabolism or clearance precaution only when the product contributes relevant caffeine exposure; does not establish absorption or a botanical-specific risk magnitude.
Single-dose healthy-volunteer study, not maintenance clozapine patients; abstract-only access after failed full-text request.
Source 3: coffee-phase patient study
ebi.ac.uk · Source check Sep 10, 2026
Population: 12 hospitalized patients entered coffee and decaffeinated-coffee seven-day phases; two were excluded. Six fully compliant participants had a separate analysis.
Six fully compliant participants had 26% higher clozapine trough concentrations, not statistically significant (95% CI -3% to 54%, P=.07). Combined data showed 20% higher concentrations (95% CI 3% to 37%, P=.03).
How this applies: Direct caffeine-clozapine evidence, indirect for this botanical. Supports a constituent-based metabolism or clearance precaution only when the product contributes relevant caffeine exposure; does not establish absorption or a botanical-specific risk magnitude.
Do not merge the compliant-subgroup and combined estimates or state that all 12 were analyzed; abstract does not establish a universal caffeine dose threshold.
Source 4: Original analytical product study
api.ods.od.nih.gov · Source check Sep 10, 2026
Population: Botanical materials and preparations; not clozapine-treated participants.
Caffeine content varied markedly across products. Extract mass did not reliably predict caffeine. Table 2 records measurable caffeine even in some products labeled decaffeinated or caffeine free.
How this applies: Establishes botanical constituent/preparation scope only. It does not establish an exact botanical-clozapine interaction.
Historical analytical sample, not clinical co-use. The web summary reports zero for liquid extracts, whereas the linked report table lists 3.9 and 27.0 mg/day; no categorical caffeine-free-liquid conclusion is used. The range is not a clozapine safety limit.
Research assessment: · Open full citations ↗
Review and change history
- Publication status
- Published research summary
- Clinical review
- Not yet recorded
| Date | Update |
|---|---|
| Article prepared | |
| Sources checked and article drafted. | |
| Clarified practical advice about timing and clinician-directed dose changes. | |
| Research summary published |
Article revision: f893d25dd4b4bf13
This guide brings together the evidence records used by our interaction checker. Each finding retains its own preparation limits, research date, and source summaries.
Full citations require verification. Reading this answer and the source summaries does not.
Taking other supplements or medications?
Use the checker to explore your other combinations. Ask a pharmacist to review the exact products, amounts and medical conditions in your complete list.
Open the interaction checkerInformation, not medical advice. Do not change prescribed treatment based on this guide.